Title of Invention	METHOD TO DETECT A MODE-GEAR MISMATCH DURING STEADY STATE OPERATION OF AN ELECTRO-MECHANICAL TRANSMISSION AND MODIFYING THE OPERATION OF POWERTRAIN
Abstract	Control of operation of a hybrid powertrain is provided, wherein mechanical power flow to an output is controlled through selective actuation of torque-transfer clutches. Electric machines are coupled to an energy storage system for electric power flow. The electro-mechanical transmission is operated in a continuously variable operating range state, and, operation of the transmission is monitored. Absence of a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission is determined. Presence of a mismatch between the commanded operating range state and the actual operating state of the transmission may be determined. Operation of the powertrain is modified when a mismatch between the commanded operating range state and the actual operating state of the transmission is detected.

Title of Invention

METHOD TO DETECT A MODE-GEAR MISMATCH DURING STEADY STATE OPERATION OF AN ELECTRO-MECHANICAL TRANSMISSION AND MODIFYING THE OPERATION OF POWERTRAIN

Abstract

Control of operation of a hybrid powertrain is provided, wherein mechanical power flow to an output is controlled through selective actuation of torque-transfer clutches. Electric machines are coupled to an energy storage system for electric power flow. The electro-mechanical transmission is operated in a continuously variable operating range state, and, operation of the transmission is monitored. Absence of a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission is determined. Presence of a mismatch between the commanded operating range state and the actual operating state of the transmission may be determined. Operation of the powertrain is modified when a mismatch between the commanded operating range state and the actual operating state of the transmission is detected.

Full Text	METHOD AND APPARATUS TO DETECT A MODE-GEAR MISMATCH DURING STEADY STATE OPERATION OF AN ELECTRO MECHANICAL TRANSMISSION TECHNICAL FIELD [0001] This disclosure pertains generally to control systems for electro- mechanical transmissions. BACKGROUND OF THE INVENTION [0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. [0003] Powertrain architectures comprise torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to a vehicle driveline. One such transmission includes a two-mode, compound-split, electro-mechanical transmission which utilizes an input member for receiving motive torque from a prime mover power source, typically an internal combustion engine, and an output member for delivering motive torque from the transmission to the vehicle driveline and to wheels of the vehicle. Electric machines, operatively connected to an electrical energy storage device, comprise motor/generators operable to generate motive torque for input to the transmission, independently of torque input from the internal combustion engine. The electric machines are further operable to transform vehicle kinetic energy, transmitted through the vehicle driveline, to electrical energy that is storable in the electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the powertrain system, including controlling transmission gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange between the electrical energy storage device and the electric machines. [0004] The exemplary electro-mechanical transmissions are selectively operative in fixed gear operation and continuously variable operation through actuation of torque-transfer clutches, typically employing a hydraulic circuit to effect clutch actuation. A fixed gear operation occurs when the ratio of the rotational speed of the transmission output member to the rotational speed of the input member is constant, typically due to actuation of one or more torque- transfer clutches. A continuously variable operation occurs when the ratio of the rotational speed of the transmission output member to the rotational speed of the input member is variable based upon operating speeds of one or more electric machines. The electric machines can be selectively connected to the output member via actuation of a clutch, or directly by fixed mechanical connections. Clutch actuation and deactivation is typically effected through a hydraulic circuit, including electrically-actuated hydraulic flow management valves, pressure control solenoids, and pressure monitoring devices controlled by a control module. [0005] During operation, there is a need to monitor operation to identify a mismatch between a commanded operating range state and an actual operating range state. In such a situation, a mode-gear mismatch may occur, including for example the control system commanding continuously variable operation, when the transmission is actually operating in fixed gear operation. However, operation of the powertrain may mask presence of the mismatch. When this occurs, the control system tries to force engine speed to a calculated optimum speed intended for a continuously variable operation. The result may be an unwanted change in operation of the vehicle. There is a need to effectively identify absence of a mismatch, identify presence of a mismatch, and mitigate effects of any mismatch. SUMMARY OF THE INVENTION [0006] A powertrain includes an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and a pair of electric machines for mechanical power flow to an output through selective actuation of a plurality of torque-transfer clutches. The electric machines are electrically-operatively coupled to an energy storage system for electric power flow therebetween. A method for controlling the powertrain includes commanding operation of the electro-mechanical transmission in a continuously variable operating range state and monitoring operation of the transmission. Absence of a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission is determined. And, presence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission is detected. When a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission is detected, powertrain operation is modified. BRIEF DESCRIPTION OF THE DRAWINGS [0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in accordance with an embodiment of the present invention; [0008] Fig. 2 is a schematic diagram of an exemplary architecture for a control system and powertrain, in accordance with an embodiment of the present invention; [0009] Fig. 3 is a graphical depiction, in accordance with an embodiment of the present invention; [0010] Fig. 4 is a schematic diagram of a hydraulic circuit, in accordance with an embodiment of the present invention; and, [0011] Fig. 5 is an algorithmic flowchart, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT [0012] Referring now to the drawings, wherein the depictions are for the purpose of illustrating embodiments of the invention only and not for the purpose of limiting the same, Figs. 1 and 2 depict a system comprising an engine 14, transmission 10, driveline 90, control system, and hydraulic control circuit 42 (Fig. 4) which has been constructed in accordance with an embodiment of the present invention. The exemplary hybrid powertrain system is configured to execute the control scheme depicted hereinbelow with reference to Fig. 5. Mechanical aspects of the exemplary transmission 10 are disclosed in detail in commonly assigned U.S. Patent No. 6,953,409, which is incorporated herein by reference. The exemplary two-mode, compound-split, electro-mechanical hybrid transmission embodying the concepts of the present invention is depicted in Fig. 1. The transmission 10 includes an input shaft 12 having an input speed, N1 that is preferably driven by the internal combustion engine 14, and an output shaft 64 having an output rotational speed, No. [0013] The exemplary engine 14 comprises a multi-cylinder internal combustion engine selectively operative in several states to transmit torque to the transmission via shaft 12, and can be either a spark-ignition or a compression-ignition engine. The engine 14 has a crankshaft having characteristic speed NE which is operatively connected to the transmission input shaft 12. The output of the engine, comprising speed NE and output torque TE can differ from transmission input speed NI and engine input torque TI when a torque management device (not shown) is placed therebetween. [0014] The transmission 10 utilizes three planetary-gear sets 24, 26 and 28, and four torque-transmitting devices, i.e., clutches Cl 70, C2 62, C3 73, and C4 75. An electro-hydraulic control system 42, preferably controlled by transmission control module (TCM) 17, is operative to control actuation and deactivation of the clutches. Clutches C2 and C4 preferably comprise hydraulically-actuated rotating friction clutches. Clutches Cl and C3 preferably comprise comprising hydraulically-actuated stationary devices grounded to the transmission case 68. Each clutch is preferably hydraulically actuated, receiving pressurized hydraulic fluid from a pump 88 via an electro- hydraulic control circuit 42. [0015] There is a first electric machine comprising a motor/generator 56, referred to as MG-A, and a second electric machine comprising a motor/generator 72, referred to as MG-B operatively connected to the transmission via the planetary gears. Each of the machines includes a stator, a rotor, and a resolver assembly 80, 82. The stator for each machine is grounded to outer transmission case 68, and includes a stator core with coiled electrical windings extending therefrom. The rotor for MG-A 56 is supported on a hub plate gear that is operably attached to output shaft 60 via carrier 26. The rotor for MG-B 72 is attached to sleeve shaft hub 66. The resolver assemblies 80, 82 are appropriately positioned and assembled on MG-A 56 and MG-B 72. Each resolver assembly 80, 82 comprises a known variable reluctance device including a resolver stator, operably connected to the stator of each electric machine, and a resolver rotor, operably connected to the rotor of each electric machine. Each resolver 80, 82 comprises a sensing device adapted to sense rotational position of the resolver stator relative to the resolver rotor, and identify the rotational position. Signals output from the resolvers are interpreted to provide rotational speeds for MG-A 56 and MG-B 72, referred to as NA and NB. Transmission output shaft 64 is operably connected to a vehicle driveline 90 to provide motive output torque, To, to vehicle wheels. There is a transmission output speed sensor 84, operative to monitor rotational speed of the output shaft 64. Each of the vehicle wheels is equipped with a sensor 94 adapted to monitor wheel speed, the output of which is monitored by the control system and used to determine absolute wheel speed and relative wheel speed for braking control, traction control, and vehicle acceleration management. [0016] The transmission 10 receives input torque from the torque-generative devices, including the engine 14, and MG-A 56 and MG-B 72, referred to as 'TI', 'TA', and 'TB' respectively, as a result of energy conversion from fuel or electrical potential stored in an electrical energy storage device (ESD) 74. The ESD 74 is high voltage DC-coupled to transmission power inverter module (TPIM) 19 via DC transfer conductors 27. The TPIM 19 is an element of the control system described hereinafter with regard to Fig. 2. The TPIM 19 transmits electrical energy to and from MG-A 56 by transfer conductors 29, and the TPIM 19 similarly transmits electrical energy to and from MG-B 72 by transfer conductors 31. Electrical current is transmitted to and from the ESD 74 in accordance with whether the ESD 74 is being charged or discharged. TPIM 19 includes the pair of power inverters and respective motor control modules configured to receive motor control commands and control inverter states therefrom for providing motor drive or regeneration functionality. Preferably, MG-A 56 and MG-B 72 are three-phase AC machines each having a rotor operable to rotate within a stator that is mounted on a case of the transmission. The inverters comprise known complementary three-phase power electronics devices. [0017] Referring now to Fig. 2, a schematic block diagram of the control system, comprising a distributed control module architecture, is shown. The elements described hereinafter comprise a subset of an overall vehicle control architecture, and are operable to provide coordinated system control of the powertrain system described herein. The control system is operable to synthesize pertinent information and inputs, and execute algorithms to control various actuators to achieve control targets, including such parameters as fuel economy, emissions, performance, driveability, and protection of hardware, including batteries of ESD 74 and MG-A 56 and MG-B 72. The distributed control module architecture includes engine control module (ECM) 23, transmission control module (TCM) 17, battery pack control module (BPCM) 21, and TPIM 19. A hybrid control module (HCP) 5 provides overarching control and coordination of the aforementioned control modules. There is a User Interface (UI) 13 operably connected to a plurality of devices through which a vehicle operator typically controls or directs operation of the powertrain including the transmission 10, including an operator torque request (To_req) and operator brake request (BRAKE). Exemplary vehicle input devices to the UI 13 include an accelerator pedal, a brake pedal, a transmission gear selector, and a vehicle speed cruise control. Each of the aforementioned control modules communicates with other control modules, sensors, and actuators via a local area network (LAN) bus 6. The LAN bus 6 allows for structured communication of control parameters and commands among the various control modules. The specific communication protocol utilized is application-specific. The LAN bus and appropriate protocols provide for robust messaging and multi-control module interfacing between the aforementioned control modules, and other control modules providing functionality such as antilock braking, traction control, and vehicle stability. [0018] The HCP 5 provides overarching control of the hybrid powertrain system, serving to coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21. Based upon various input signals from the UI 13 and the powertrain, including the battery pack, the HCP 5 generates various commands, including: the operator torque request (Toreq), the engine input torque TI, clutch torque, (TCL_N) for the N various torque-transfer clutches Cl, C2, C3, C4 of the transmission 10; and motor torques TAand TB for MG-A 56 and MG-B 72. The TCM 17 is operatively connected to the electro-hydraulic control circuit 42, including for monitoring various pressure sensing devices (not shown) and generating and executing control signals for various solenoids to control pressure switches and control valves contained therein. [0019] The ECM 23 is operably connected to the engine 14, and functions to acquire data from a variety of sensors and control a variety of actuators, respectively, of the engine 14 over a plurality of discrete lines collectively shown as aggregate line 35. The ECM 23 receives the engine input torque command from the HCP 5, and generates a desired axle torque, and an indication of actual engine input torque, T,, to the transmission, which is communicated to the HCP 5. For simplicity, ECM 23 is shown generally having bi-directional interface with engine 14 via aggregate line 35. Various other parameters that may be sensed by ECM 23 include engine coolant temperature, engine input speed, NE, to shaft 12 (which translate to transmission input speed, NI) manifold pressure, ambient air temperature, and ambient pressure. Various actuators that may be controlled by the ECM 23 include fuel injectors, ignition modules, and throttle control modules. [0020] The TCM 17 is operably connected to the transmission 10 and functions to acquire data from a variety of sensors and provide command signals to the transmission. Inputs from the TCM ] 7 to the HCP 5 include estimated clutch torques (TCL_N) for each of the N clutches, i.e., C1, C2, C3, and C4, and rotational output speed, No, of the output shaft 64. Other actuators and sensors may be used to provide additional information from the TCM to the HCP for control purposes. The TCM 17 monitors inputs from pressure switches and selectively actuates pressure control solenoids and shift solenoids to actuate various clutches to achieve various transmission operating modes, as described hereinbelow. [0021] The BPCM 21 is signally connected one or more sensors operable to monitor electrical current or voltage parameters of the ESD 74 to provide information about the state of the batteries to the HCP 5. Such information includes battery state-of-charge, amp-hour throughput, battery temperature, battery voltage and available battery power. [0022] Each of the aforementioned control modules is preferably a general- purpose digital computer generally comprising a microprocessor or central processing unit, storage mediums comprising read only memory (ROM), random access memory (RAM), electrically programmable read only memory (EPROM), high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, and input/output circuitry and devices (I/O) and appropriate signal conditioning and buffer circuitry. Each control module has a set of control algorithms, comprising resident program instructions and calibrations stored in ROM and executed to provide the respective functions of each computer. Information transfer between the various computers is preferably accomplished using the aforementioned LAN 6. [0023] Algorithms for control and state estimation in each of the control modules are typically executed during preset loop cycles such that each algorithm is executed at least once each loop cycle. Algorithms stored in the non-volatile memory devices are executed by one of the central processing units and are operable to monitor inputs from the sensing devices and execute control and diagnostic routines to control operation of the respective device, using preset calibrations. Loop cycles are typically executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engine and vehicle operation. Alternatively, algorithms may be executed in response to occurrence of an event. [0024] Referring now to Fig. 3, the exemplary two-mode, compound-split, electro-mechanical transmission operates in one of several operating range states comprising fixed gear operation and continuously variable operation, described with reference to Table 1, below. [0025] The various transmission operating range states described in the table indicate which of the specific clutches Cl, C2, C3, and CA are engaged or actuated for each of the operating range states. A first continuously variable operating range state, i.e., Mode I, is selected when clutch Cl 70 is actuated in order to "ground" the outer gear member of the third planetary gear set 28. The engine 14 can be either on or off. A second continuously variable operating range state, i.e., Mode II, is selected when clutch C1 70 is released and clutch C2 62 is simultaneously actuated to connect the shaft 60 to the carrier of the third planetary gear set 28. Again, the engine 14 can be either on or off. For purposes of this description, Engine Off is defined by engine input speed, NE, being equal to zero revolutions per minute (RPM), i.e., the engine crankshaft is not rotating, typically as a result of the engine being decoupled from the transmission. Other factors outside the scope of this disclosure affect when the electric machines 56, 72 operate as motors and generators, and are not discussed herein. [0026] Mode I and Mode II are characterized by single clutch applications, i.e., either clutch Cl 62 or C2 70, and by the controlled speed and torque of the electric machines 56 and 72, which can be referred to as a continuously variable transmission mode. Certain operating rage states are described below in which fixed gear ratios are achieved by applying an additional clutch. This additional clutch may be clutch C3 73 or C4 75, as shown in the table, above. When the additional clutch is applied, fixed gear operation of input-to-output speed of the transmission, i.e., NI/No, is achieved. During fixed gear operation, the rotations of machines MG-A 56 and MG-B 72, i.e., NA and NB, are dependent on internal rotation of the mechanism as defined by the clutching and proportional to the input speed measured at shaft 12. [0027] In response to an operator's action, as captured by the UI 13, the supervisory HCP control module 5 and one or more of the other control modules determine the operator torque request to be executed at shaft 64. Final vehicle acceleration is affected by other factors, including, e.g., road load, road grade, and vehicle mass. The transmission operating range state is determined for the exemplary transmission based upon a variety of operating characteristics of the powertrain. This includes an operator demand for torque, typically communicated through inputs to the UI 13 as previously described. Additionally, a demand for output torque is predicated on external conditions, including, e.g., road grade, road surface conditions, or wind load. The transmission operating range state may be predicated on a powertrain torque demand caused by a control module command to operate one of the electric machines as an electrical generator or as an electric motor. The transmission operating range state can be determined by an optimization algorithm or routine operable to determine optimum system efficiency based upon operator demand for power, battery state of charge, and energy efficiencies of the engine 14 and MG-A 56 and MG-B 72. The control system manages torque inputs from the engine 14 and MG-A 56 and MG-B 72 based upon an outcome of the executed optimization routine, and system optimization occurs to optimize system efficiencies to improve fuel economy and manage battery charging. Furthermore, operation can be determined based upon a fault in a component or system. The HCP 5 monitors the parametric states of the torque-generative devices, and determines the output of the transmission required to arrive at the desired torque output, as described hereinbelow. Under the direction of the HCP 5, the transmission 10 operates over a range of output speeds from slow to fast in order to meet the operator demand. [0028] The energy storage system and electric machines MG-A 56 and MG- B 72 are electrically-operatively coupled for power flow therebetween. Furthermore, the engine, the electric machines, and the electro-mechanical transmission are mechanically-operatively coupled to transmit power therebetween to generate a power flow to the output. In Mode I operation, the transmission operates as an input-split electrically variable transmission (EVT). In Mode II operation, the transmission operates as a compound-split EVT. While operating in either of these two modes, the control system performs closed loop control on an engine speed which optimizes fuel economy while still meeting the torque request and given power constraints. It then commands motor speeds to vary the input-to-output speed ratio to accelerate the vehicle, in response to the operator torque request. Through use of the two additional clutches, the transmission also has the capability of achieving one of four fixed gear ratios. While operating in a fixed gear, the vehicle acts as a parallel hybrid and the motors are used only for boosting and braking/regeneration the vehicle. [0029] Referring to Fig. 4, a schematic diagram is depicted which provides a more detailed description of the exemplary electro-hydraulic system for controlling flow of hydraulic fluid in the exemplary transmission. The main hydraulic pump 88, driven off the input shaft 12 from the engine 14, and auxiliary pump 110, operatively electrically controlled by the TPIM 19, provides pressurized fluid to the hydraulic circuit 42 through valve 140. The auxiliary pump 110 preferably comprises an electrically-powered pump of an appropriate size and capacity to provide sufficient flow of pressurized hydraulic fluid into the hydraulic system when operational. Pressurized hydraulic fluid flows into electro-hydraulic control circuit 42, which is operable to selectively distribute hydraulic pressure to a series of devices, including the torque-transfer clutches C\ 70, C2 62, C3 73, and C4 75, active cooling circuits for machines A and B, and a base cooling circuit for cooling and lubricating the transmission 10 via passages 142, 144 (not depicted in detail). As previously stated, the TCM 17 is preferably operable to actuate the various clutches to achieve various transmission operation through selective actuation of hydraulic circuit flow control devices comprising variable pressure control solenoids (PCS) PCS1 108, PCS2 112, PCS3 114, PCS4 116 and solenoid-controlled flow management valves X-valve 119 and Y-valve 121. The circuit is fluidly connected to pressure switches PS1, PS2, PS3, and PS4 via passages 124, 122, 126, and 128, respectively. There is an inlet spool valve 107. The pressure control solenoid PCS1 108 has a control position of normally high and is operative to modulate fluidic pressure in the hydraulic circuit through fluidic interaction with controllable pressure regulator 109. Controllable pressure regulator 109, not shown in detail, interacts with PCS1 108 to control hydraulic pressure in the hydraulic circuit 42 over a range of pressures, depending upon operating conditions as described hereinafter. Pressure control solenoid PCS2 112 has a control position of normally low, and is fluidly connected to spool valve 113 and operative to effect flow therethrough when actuated. Spool valve 113 is fluidly connected to pressure switch PS3 via passage 126. Pressure control solenoid PCS3 114 has a control position of normally low, and is fluidly connected to spool valve 115 and operative to effect flow therethrough when actuated. Spool valve 115 is fluidly connected to pressure switch PS1 via passage 124. Pressure control solenoid PCS4 116 has a control position of normally low, and is fluidly connected to spool valve 117 and operative to effect flow therethrough when actuated. Spool valve 117 is fluidly connected to pressure switch PS4 via passage 128. [0030] The X-Valve 119 and Y-Valve 121 each comprise flow management valves controlled by solenoids 118, 120, respectively, in the exemplary system, and have control states of High (1) and Low (0). The control states refer to positions of each valve with which to control flow to different devices in the hydraulic circuit 42 and the transmission 10. The X-valve 119 is operative to direct pressurized fluid to clutches C3 and C4 and cooling systems for stators of MG-A 56 and MG-B 72 via fluidic passages 136, 138, 144, 142 respectively, depending upon the source of the fluidic input, as is described hereinafter. The Y-valve 121 is operative to direct pressurized fluid to clutches Cl and C2 via fluidic passages 132 and 134 respectively, depending upon the source of the fluidic input, as is described hereinafter. The Y-valve 121 is fluidly connected to pressure switch PS2 via passage 122. A more detailed description of the exemplary electro-hydraulic control circuit 42 is provided in commonly assigned U.S. Patent Application No. 11/263,216, which is incorporated herein by reference. [0031] An exemplary logic table to accomplish control of the exemplary electro-hydraulic control circuit 42 is provided with reference to Table 2, below. [0032] Selective control of the X and Y valves and actuation of the solenoids PCS2, PCS3, and PCS4 facilitate flow of hydraulic fluid to actuate clutches C1, C2, C3, and C4, and provide cooling for the stators of MG-A 56 and MG- B 72. [0033] In operation, one of the fixed gear and continuously variable operating range states is determined for the exemplary transmission based upon a variety of operating characteristics of the powertrain. This includes an operator torque request, typically communicated through inputs to the UI 13 as previously described. Additionally, a demand for output torque is predicated on external conditions, including, e.g., road grade, road surface conditions, or wind load. Transmission operating range state may be predicated on a powertrain torque demand caused by a control module command to operate of the electric machines as an electrical generator or as an electrical motor. Operation can be determined by an optimization algorithm or routine operable to determine optimum system efficiency based upon operator demand for power, battery state of charge, and energy efficiencies of the engine 14 and MG-A 56 and MG-B 72. The control system manages torque inputs from the engine 14 and MG-A 56 and MG-B 72 based upon an outcome of the executed optimization routine, and system optimization occurs to optimize system efficiencies to improve fuel economy and manage battery charging. Furthermore, operation can be determined based upon a fault in a component or system. [0034] Referring now to the transmission described with reference to Figs. 1, 2, 3, and 4, and Tables 1 and 2, specific aspects of the transmission and control system are described herein. The control system is operative to selectively actuate the pressure control devices and the flow management valves based upon a demand for torque, presence of a fault, and temperatures of the electric motors. The control system selectively commands one of a low- range continuously variable operation, a high-range continuously variable operation, a low range state, and a high range state based upon selective actuation of the X-valve 118 and Y-valve 120 flow management valves. The control system effects actuation of the stator cooling system for the first electric machine (MG-A Stator Cool), the stator cooling system for the second electric machine (MG-B Stator Cool), and the first hydraulically-actuated clutch (C1) based upon selective actuation of the pressure control devices PCS2, PCS3, and PCS4 when the low-range continuously variable operation has been commanded. Furthermore, the control system is operative to effect actuation of the stator cooling system for MG-A 56, stator cooling system for MG-B 72, and the second hydraulically-actuated clutch C2 based upon selective actuation of the pressure control devices when a high-range continuously variable operation has been commanded. The control system is operative to effect actuation of the first, second, and fourth hydraulically- actuated clutches (i.e., C1, C2, C4) based upon selective actuation of the pressure control devices when a low-range state has been commanded, comprising operation in one of FG1, FG2, Mode I via selective actuation of the clutches. The control system is operative to effect actuation of the second, third, and fourth hydraulically-actuated clutches (i.e., C2, C3, C4) based upon selective actuation of the pressure control devices when a high-range state has been commanded, comprising operation in one of FG3, FG4, and Mode II via selective actuation of the clutches. [0035] As previously stated, fluid output from each of the second, third and fourth pressure control devices (i.e., PCS2, PCS3, and PCS4) is selectively mapped to one of the four hydraulically-actuated clutches and stator cooling systems for MG-A 56 and MG-B 72 based upon commanded positions of the first and second flow management valves. Therefore, selective actuation of PCS2 effects flow of hydraulic fluid to provide cooling to the stator of MG-B 72, when both the X-valve and the Y-valve are commanded to Low. Selective actuation of PCS2 effects flow of hydraulic fluid to actuate clutch C2 when either of the X-valve and the Y-valve are commanded to High. Selective actuation of PCS3 effects flow of hydraulic fluid to actuate clutch Cl when both the X-valve and the Y-valve are commanded to Low. Selective actuation of PCS3 effects flow of hydraulic fluid to provide cooling to the stator of MG- B 72 when the X-valve is commanded to Low and the Y-valve is commanded to High. Selective actuation of PCS3 effects flow of hydraulic fluid to actuate clutch Cl when the X-valve is commanded to High and the Y-valve is commanded to Low. Selective actuation of PCS3 effects flow of hydraulic fluid to actuate clutch C3 when both the X-valve and the Y-valve are commanded to High. Selective actuation of PCS4 effects flow of hydraulic fluid to provide cooling to the stator of MG-A 56 when the X-valve is commanded to Low, regardless of the position to which the Y-valve is commanded. Selective actuation of PCS4 effects flow of hydraulic fluid to actuate clutch C4 when the X-valve is commanded to High, regardless of the position to which the Y-valve is commanded. [0036] Referring now to the flowchart 400 depicted in Fig. 5, with reference to the exemplary transmission described with reference to Figs. 1, 2, 3, and 4, and Tables 1 and 2, specific aspects of controlling operation of the exemplary transmission and control system are described. In operation, the electro- mechanical transmission is commanded by one of the control modules to operate in one of the continuously variable operating range states (Step 410), i.e., either Mode I or II, through selective actuation of either clutch C1 or clutch C2. Operation of the transmission is monitored, including the rotational speeds of various elements, including specifically transmission speeds No, NA, and NB (Step 412). Other elements are monitored, as required for operation of the system, e.g., NE, TA, and TB. An absence of a mismatch between the commanded operating range state and the actual operating state of the transmission is determined based upon the monitored operation of the transmission (Step 414). Presence of a mismatch between the commanded operating range state and the actual operating state of the transmission is detected based upon the monitored operation of the transmission, including presence of excess motor torque and clutch slippage (Steps 416, 418). The commanded operation of the internal combustion engine is modified when a mismatch between the commanded operating range state and an actual operating state of the transmission is detected (Step 420). This is now described in detail. [0037] A potential powertrain system fault includes a mismatch between a commanded operating range state and an actual operating state of the transmission. This includes the control system commanding operation in one of the continuously variable operating range states, whereas the transmission actually operates in one of the fixed gear operating range states. This is referred to as a mode-gear mismatch. During ongoing operation, the control system commands either of continuously variable operating range states, Mode 1 and Mode II, as depicted in Table 2. In each Mode operation only one clutch is applied for the exemplary embodiment, which corresponds to one pressure control solenoid (PCS) in the hydraulically high state. The hydraulic system is designed such that if a hardware fault occurs affecting either of the remaining two pressure control solenoids while operating in either Mode I or Mode II, the only result is motor stator cooling. [0038] It can be seen that in both Mode I or Mode II, the X-valve 119 is in a hydraulically low state. If there is a fault in the X-valve causing it to remain in a hydraulically high state, a single fault in one of the PCS devices can lead to an unacceptable operating condition. For example, were the X valve to have a fault causing it to remain 'HIGH', the vehicle continues to operate in Mode I by operating in the 'Low Range' state and commanding PCS3 hydraulically high. However, any subsequent fault on PCS2 in HIGH position may result in application of clutch C2, with a corresponding mismatch, in that Mode I is commanded, whereas FG2 is executed in the transmission. [0039] A first tactic for detecting a mode-gear mismatch includes affirmatively determining an absence of any mode-gear mismatch by monitoring clutch slippage. This detection tactic comprises monitoring and detecting clutch slippage during steady state operation in one of Mode I and II, wherein only a single clutch is applied, i.e., commanded actuated. During operation, only a single clutch, i.e., either C1 or C2, is expected to demonstrate clutch slippage at or near-zero during any given period of time. When there is a significant amount of slip across a clutch for a period of time it can be determined that the specific clutch is not actuated, and there is no mode-gear mismatch. Thus, in Mode I, Clutch C1 is commanded actuated, with slippage occurring across each of clutches C2, C3, and C4. Thus, in Mode II, Clutch C2 is commanded actuated, with slippage occurring across each of clutches C1, C3, and C4. When such slippage conditions are determined for the clutches whose actuation is not commanded, the control strategy affirms the absence of a mode-gear mismatch. However, if a condition occurs wherein it is determined that one of the unactuated clutches has slippage at or near zero slip speed for more than a minimal amount of time, then there is a potential that the clutch is actuated, and a potential for a mode-gear mismatch. Slippage across each of the clutches is determined based upon the various measured rotational speeds of NE, No, NA, and NB. [0040] A second tactic for detecting a mode-gear mismatch includes affirmatively determining an absence of a mode-gear mismatch by monitoring engine input speed. During operation in Mode I or Mode II, the control system controls input speed, NI, to a calculated optimum engine speed, Ni_opt. In closed loop control around the optimum input speed, Niopt, the input speed is expected to follow an optimum speed profile, determined based upon operating conditions and operator inputs. In the system described hereinabove, the relationship between various speeds is fixed by the hardware, comprising (NA + NB)/2 = NI. In this tactic, the motor speeds NA and NB are measured with the resolvers 80, 82, and input speed, NI, is calculated therefrom. In the event of a mode-gear mismatch, it is likely that there is a significant difference between the current engine speed, NI, and the optimum input speed, Niopt, which is determined as a part of the engine and system operation. Therefore, when the input speed, NI, follows the optimum input speed, Niopt, the control strategy affirms the absence of a mode-gear mismatch, and when there is a difference in the input speed and the optimum input speed, there is potentially a mode-gear mismatch. [0041] When the outcomes of the first and second tactics are unable to affirm the absence of a mode-gear mismatch, additional tactics are executed to detect the presence of a mode-gear mismatch. For example, during steady state operation a mode-gear mismatch may occur which is unperceivable to the vehicle operator, or results in a light acceleration event. A third tactic for detecting a mode-gear mismatch includes affirmatively detecting presence of the mode-gear mismatch by monitoring motor torque from both of the electric machines. During operation in either Mode I or Mode II, the control system calculates the motor torque needed from both the electric machines to achieve the optimum closed loop engine speed control, Niopt. The current motor torques from the machines are determined based upon electric power transferred thereto. Excess torque for each motor, based upon a difference between the current motor torque and calculated motor torque, is calculated. A calculation indicating a significant amount of excess torque being applied by one of the electric machines to one of the clutches indicates presence of a mode-gear mismatch. [0042] A fourth tactic for detecting a mode-gear mismatch includes affirmatively detecting presence of the mode-gear mismatch by monitoring slippage of the clutches to detect zero-slip conditions. During operation in either Mode I or Mode II, a clutch which is not actuated is expected to have slippage. By monitoring clutch slippage, a zero-slip condition can be determined. When the output speed is not decelerating, then slip speed of an oncoming clutch eventually reaches near-zero speed (steady state), even during a mode-gear mismatch. Therefore, when there is no clutch slippage in an unapplied clutch, the control strategy is able to detect a mode-gear mismatch. [0043] When a mode-gear mismatch is experienced and detected, operation of the powertrain is preferably modified in a timely manner. Modifying powertrain operation includes disabling the closed loop engine speed control, to prevent the control system from varying the engine input speed, preferably within 200 msec of the detection. This includes sending a software control flag to the control system to disable the closed loop engine control, and subsequently informing the operator by illuminating a dashboard lamp. When affirmative pass is subsequently detected, i.e., an outcome of executing the first or second tactics results in a pass condition for a calibratable length of time, the closed loop engine control is preferably re-enabled. [0044] There are preferably different conditions for affirmatively determining an absence of the mode-gear mismatch, and affirmatively determining a presence of a mode-gear mismatch. Therefore, there can be a condition wherein a vehicle may both determine an absence and determine a presence of a mode-gear mismatch at the same time. This may occur during a short time window when the vehicle is experiencing a sharp deceleration due to an oncoming clutch which still has a slip speed above the threshold of the pass criteria. For this reason the action of disabling the closed loop speed control continues until the pass condition has been met for a calibratable amount of time, typically less than four seconds. If the clutch continues to be applied, the clutch slip speed drops below the pass condition threshold within the calibratable amount of time and engine closed loop remains disabled. If the clutch is no longer applied, and the test continues to pass, engine closed loop control is re-enabled. [0045] The invention has been described with specific reference to the disclosed embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the invention. Having thus described the invention, it is claimed: 1. Method for operating a powertrain including an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and a pair of electric machines for mechanical power flow to an output through selective actuation of a plurality of torque-transfer clutches, said electric machines electrically-operatively coupled to an energy storage system for electric power flow therebetween, the method comprising: commanding operation of the electro-mechanical transmission in a continuously variable operating range state; monitoring operation of the transmission; determining absence of a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission; detecting presence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission; and, modifying operation of the powertrain when a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission is detected. 2. The method of claim 1, wherein commanding operation of the electro- mechanical transmission in a continuously variable operating range state comprises selectively actuating a single one of the torque-transfer clutches. 3. The method of claim 2, wherein monitoring operation of the transmission comprises monitoring rotational speeds of inputs and an output of the transmission and monitoring torque output from the electric machines. 4. The method of claim 3, wherein determining the absence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission comprises: determining slippage across each of the clutches based upon the monitored rotational speeds of the inputs and the output of the transmission and the electric machines; and, determining clutch slippage is greater than zero for each of the torque transfer clutches not selectively actuated. 5. The method of claim 4, wherein determining absence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission further comprises: determining an optimum input speed, and, determining the input speed is substantially close to the optimum input speed. 6. The method of claim 5, wherein detecting a presence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission further comprises: calculating motor torque from the electric machines to achieve the optimum input speed; and, determining application of excess torque to one of the clutches. 7. The method of claim 6, wherein detecting the presence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission comprises determining clutch slippage is substantially near zero for only the selectively actuated single one of the torque-transfer clutches. 8. The method of claim 1, wherein determining absence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission comprises: determining an optimum input speed, and, determining the input speed is substantially close to the optimum input speed. 9. The method of claim 1, wherein determining absence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission comprises: determining slippage across each of the clutches based upon monitored rotational speeds of an input and an output of the transmission and the electric machines; and, determining clutch slippage is greater than zero for each of the torque transfer clutches not selectively actuated. 10. The method of claim 1, wherein determining the absence of a mismatch between the commanded continuously variable operating range state and the actual operating state of the transmission comprises: determining slippage across each of the clutches based upon monitored rotational speeds of an input and an output of the transmission and the electric machines; determining clutch slippage is greater than zero for each of the torque transfer clutches not selectively actuated; and, determining clutch slippage is substantially zero for only the selectively actuated single one of the torque-transfer clutches. 11. The method of claim 1, wherein modifying operation of the powertrain when a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission is detected comprises modifying a commanded operation of the internal combustion engine. 12. Method for operating a powertrain including an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and a pair of electric machines for mechanical power flow to an output through selective actuation of a plurality of torque-transfer clutches, said electric machines electrically-operatively coupled to an energy storage system for electric power flow therebetween, the method comprising: commanding operation of the electro-mechanical transmission in a continuously variable operating range state; controlling the internal combustion engine in closed loop engine speed control based upon an optimum engine speed; monitoring operation of the transmission; determining absence of a mismatch between the commanded operation of the electro-mechanical transmission and an actual operation of the electro- mechanical transmission; detecting presence of a mismatch between the commanded operation of the electro-mechanical transmission and the actual operation of the electro- mechanical transmission; and, disabling the closed loop engine speed control when a mismatch between the commanded operation of the electro-mechanical transmission and the actual operation of the electro-mechanical transmission is detected. 13. The method of claim 12, further comprising re-enabling the closed loop engine speed control when the detected mismatch between the commanded operation of the electro-mechanical transmission and the actual operation of the electro-mechanical transmission is subsequently determined absent. 14. Method for operating a powertrain including an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and a pair of electric machines for mechanical power flow to an output through selective actuation of a plurality of torque-transfer clutches, said electric machines electrically-operatively coupled to an energy storage system for electric power flow therebetween, the method comprising: selectively commanding actuation of a single one of the torque transfer clutches; determining absence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and an actual operating state of the transmission; detecting presence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission; and, modifying operation of the powertrain when a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission is detected. 15. The method of claim 14, wherein the determining absence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission comprises: determining slippage across each of the clutches based upon monitored rotational speeds of transmission inputs and the transmission and the electric machines; and, determining clutch slippage is greater than zero for each of the torque transfer clutches not selectively actuated. 16. The method of claim 14, wherein determining absence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission further comprises: determining an optimum input speed to the transmission, and, determining the input speed is substantially close to the optimum input speed to the transmission. 17. The method of claim 14, wherein detecting presence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission further comprises: calculating motor torque from the electric machines to achieve the optimum engine speed; and, determining application of excess torque to any one of the clutches. 18. The method of claim 14, wherein detecting presence of a mismatch between the commanded actuation of the single one of the torque transfer clutches and the actual operating state of the transmission comprises determining clutch slippage is substantially zero for only the selectively actuated single one of the torque-transfer clutches. Control of operation of a hybrid powertrain is provided, wherein mechanical power flow to an output is controlled through selective actuation of torque-transfer clutches. Electric machines are coupled to an energy storage system for electric power flow. The electro-mechanical transmission is operated in a continuously variable operating range state, and, operation of the transmission is monitored. Absence of a mismatch between the commanded continuously variable operating range state and an actual operating state of the transmission is determined. Presence of a mismatch between the commanded operating range state and the actual operating state of the transmission may be determined. Operation of the powertrain is modified when a mismatch between the commanded operating range state and the actual operating state of the transmission is detected.

Full Text

METHOD AND APPARATUS TO DETECT A MODE-GEAR
MISMATCH DURING STEADY STATE OPERATION
OF AN ELECTRO MECHANICAL TRANSMISSION
TECHNICAL FIELD
[0001] This disclosure pertains generally to control systems for electro-
mechanical transmissions.
BACKGROUND OF THE INVENTION
[0002] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0003] Powertrain architectures comprise torque-generative devices,
including internal combustion engines and electric machines, which transmit
torque through a transmission device to a vehicle driveline. One such
transmission includes a two-mode, compound-split, electro-mechanical
transmission which utilizes an input member for receiving motive torque from
a prime mover power source, typically an internal combustion engine, and an
output member for delivering motive torque from the transmission to the
vehicle driveline and to wheels of the vehicle. Electric machines, operatively
connected to an electrical energy storage device, comprise motor/generators
operable to generate motive torque for input to the transmission,
independently of torque input from the internal combustion engine. The
electric machines are further operable to transform vehicle kinetic energy,
transmitted through the vehicle driveline, to electrical energy that is storable in
the electrical energy storage device. A control system monitors various inputs
from the vehicle and the operator and provides operational control of the
powertrain system, including controlling transmission gear shifting,
controlling the torque-generative devices, and regulating the electrical power
interchange between the electrical energy storage device and the electric
machines.

[0004] The exemplary electro-mechanical transmissions are selectively
operative in fixed gear operation and continuously variable operation through
actuation of torque-transfer clutches, typically employing a hydraulic circuit to
effect clutch actuation. A fixed gear operation occurs when the ratio of the
rotational speed of the transmission output member to the rotational speed of
the input member is constant, typically due to actuation of one or more torque-
transfer clutches. A continuously variable operation occurs when the ratio of
the rotational speed of the transmission output member to the rotational speed
of the input member is variable based upon operating speeds of one or more
electric machines. The electric machines can be selectively connected to the
output member via actuation of a clutch, or directly by fixed mechanical
connections. Clutch actuation and deactivation is typically effected through a
hydraulic circuit, including electrically-actuated hydraulic flow management
valves, pressure control solenoids, and pressure monitoring devices controlled
by a control module.
[0005] During operation, there is a need to monitor operation to identify a
mismatch between a commanded operating range state and an actual operating
range state. In such a situation, a mode-gear mismatch may occur, including
for example the control system commanding continuously variable operation,
when the transmission is actually operating in fixed gear operation. However,
operation of the powertrain may mask presence of the mismatch. When this
occurs, the control system tries to force engine speed to a calculated optimum
speed intended for a continuously variable operation. The result may be an
unwanted change in operation of the vehicle. There is a need to effectively
identify absence of a mismatch, identify presence of a mismatch, and mitigate
effects of any mismatch.

SUMMARY OF THE INVENTION
[0006] A powertrain includes an electro-mechanical transmission
mechanically-operatively coupled to an internal combustion engine and a pair
of electric machines for mechanical power flow to an output through selective
actuation of a plurality of torque-transfer clutches. The electric machines are
electrically-operatively coupled to an energy storage system for electric power
flow therebetween. A method for controlling the powertrain includes
commanding operation of the electro-mechanical transmission in a
continuously variable operating range state and monitoring operation of the
transmission. Absence of a mismatch between the commanded continuously
variable operating range state and an actual operating state of the transmission
is determined. And, presence of a mismatch between the commanded
continuously variable operating range state and the actual operating state of
the transmission is detected. When a mismatch between the commanded
continuously variable operating range state and the actual operating state of
the transmission is detected, powertrain operation is modified.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in
accordance with an embodiment of the present invention;
[0008] Fig. 2 is a schematic diagram of an exemplary architecture for a
control system and powertrain, in accordance with an embodiment of the
present invention;
[0009] Fig. 3 is a graphical depiction, in accordance with an embodiment of
the present invention;
[0010] Fig. 4 is a schematic diagram of a hydraulic circuit, in accordance
with an embodiment of the present invention; and,
[0011] Fig. 5 is an algorithmic flowchart, in accordance with an embodiment
of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0012] Referring now to the drawings, wherein the depictions are for the
purpose of illustrating embodiments of the invention only and not for the
purpose of limiting the same, Figs. 1 and 2 depict a system comprising an
engine 14, transmission 10, driveline 90, control system, and hydraulic control
circuit 42 (Fig. 4) which has been constructed in accordance with an
embodiment of the present invention. The exemplary hybrid powertrain
system is configured to execute the control scheme depicted hereinbelow with
reference to Fig. 5. Mechanical aspects of the exemplary transmission 10 are
disclosed in detail in commonly assigned U.S. Patent No. 6,953,409, which is
incorporated herein by reference. The exemplary two-mode, compound-split,
electro-mechanical hybrid transmission embodying the concepts of the present
invention is depicted in Fig. 1. The transmission 10 includes an input shaft 12
having an input speed, N1 that is preferably driven by the internal combustion
engine 14, and an output shaft 64 having an output rotational speed, No.
[0013] The exemplary engine 14 comprises a multi-cylinder internal
combustion engine selectively operative in several states to transmit torque to
the transmission via shaft 12, and can be either a spark-ignition or a
compression-ignition engine. The engine 14 has a crankshaft having
characteristic speed NE which is operatively connected to the transmission
input shaft 12. The output of the engine, comprising speed NE and output
torque TE can differ from transmission input speed NI and engine input torque
TI when a torque management device (not shown) is placed therebetween.
[0014] The transmission 10 utilizes three planetary-gear sets 24, 26 and 28,
and four torque-transmitting devices, i.e., clutches Cl 70, C2 62, C3 73, and
C4 75. An electro-hydraulic control system 42, preferably controlled by
transmission control module (TCM) 17, is operative to control actuation and
deactivation of the clutches. Clutches C2 and C4 preferably comprise
hydraulically-actuated rotating friction clutches. Clutches Cl and C3
preferably comprise comprising hydraulically-actuated stationary devices

grounded to the transmission case 68. Each clutch is preferably hydraulically
actuated, receiving pressurized hydraulic fluid from a pump 88 via an electro-
hydraulic control circuit 42.
[0015] There is a first electric machine comprising a motor/generator 56,
referred to as MG-A, and a second electric machine comprising a
motor/generator 72, referred to as MG-B operatively connected to the
transmission via the planetary gears. Each of the machines includes a stator, a
rotor, and a resolver assembly 80, 82. The stator for each machine is
grounded to outer transmission case 68, and includes a stator core with coiled
electrical windings extending therefrom. The rotor for MG-A 56 is supported
on a hub plate gear that is operably attached to output shaft 60 via carrier 26.
The rotor for MG-B 72 is attached to sleeve shaft hub 66. The resolver
assemblies 80, 82 are appropriately positioned and assembled on MG-A 56
and MG-B 72. Each resolver assembly 80, 82 comprises a known variable
reluctance device including a resolver stator, operably connected to the stator
of each electric machine, and a resolver rotor, operably connected to the rotor
of each electric machine. Each resolver 80, 82 comprises a sensing device
adapted to sense rotational position of the resolver stator relative to the
resolver rotor, and identify the rotational position. Signals output from the
resolvers are interpreted to provide rotational speeds for MG-A 56 and MG-B
72, referred to as NA and NB. Transmission output shaft 64 is operably
connected to a vehicle driveline 90 to provide motive output torque, To, to
vehicle wheels. There is a transmission output speed sensor 84, operative to
monitor rotational speed of the output shaft 64. Each of the vehicle wheels is
equipped with a sensor 94 adapted to monitor wheel speed, the output of
which is monitored by the control system and used to determine absolute
wheel speed and relative wheel speed for braking control, traction control, and
vehicle acceleration management.
[0016] The transmission 10 receives input torque from the torque-generative
devices, including the engine 14, and MG-A 56 and MG-B 72, referred to as

'TI', 'TA', and 'TB' respectively, as a result of energy conversion from fuel or
electrical potential stored in an electrical energy storage device (ESD) 74. The
ESD 74 is high voltage DC-coupled to transmission power inverter module
(TPIM) 19 via DC transfer conductors 27. The TPIM 19 is an element of the
control system described hereinafter with regard to Fig. 2. The TPIM 19
transmits electrical energy to and from MG-A 56 by transfer conductors 29,
and the TPIM 19 similarly transmits electrical energy to and from MG-B 72
by transfer conductors 31. Electrical current is transmitted to and from the
ESD 74 in accordance with whether the ESD 74 is being charged or
discharged. TPIM 19 includes the pair of power inverters and respective motor
control modules configured to receive motor control commands and control
inverter states therefrom for providing motor drive or regeneration
functionality. Preferably, MG-A 56 and MG-B 72 are three-phase AC
machines each having a rotor operable to rotate within a stator that is mounted
on a case of the transmission. The inverters comprise known complementary
three-phase power electronics devices.
[0017] Referring now to Fig. 2, a schematic block diagram of the control
system, comprising a distributed control module architecture, is shown. The
elements described hereinafter comprise a subset of an overall vehicle control
architecture, and are operable to provide coordinated system control of the
powertrain system described herein. The control system is operable to
synthesize pertinent information and inputs, and execute algorithms to control
various actuators to achieve control targets, including such parameters as fuel
economy, emissions, performance, driveability, and protection of hardware,
including batteries of ESD 74 and MG-A 56 and MG-B 72. The distributed
control module architecture includes engine control module (ECM) 23,
transmission control module (TCM) 17, battery pack control module (BPCM)
21, and TPIM 19. A hybrid control module (HCP) 5 provides overarching
control and coordination of the aforementioned control modules. There is a
User Interface (UI) 13 operably connected to a plurality of devices through

which a vehicle operator typically controls or directs operation of the
powertrain including the transmission 10, including an operator torque request
(To_req) and operator brake request (BRAKE). Exemplary vehicle input
devices to the UI 13 include an accelerator pedal, a brake pedal, a transmission
gear selector, and a vehicle speed cruise control. Each of the aforementioned
control modules communicates with other control modules, sensors, and
actuators via a local area network (LAN) bus 6. The LAN bus 6 allows for
structured communication of control parameters and commands among the
various control modules. The specific communication protocol utilized is
application-specific. The LAN bus and appropriate protocols provide for
robust messaging and multi-control module interfacing between the
aforementioned control modules, and other control modules providing
functionality such as antilock braking, traction control, and vehicle stability.
[0018] The HCP 5 provides overarching control of the hybrid powertrain
system, serving to coordinate operation of the ECM 23, TCM 17, TPIM 19,
and BPCM 21. Based upon various input signals from the UI 13 and the
powertrain, including the battery pack, the HCP 5 generates various
commands, including: the operator torque request (Toreq), the engine input
torque TI, clutch torque, (TCL_N) for the N various torque-transfer clutches Cl,
C2, C3, C4 of the transmission 10; and motor torques TAand TB for MG-A 56
and MG-B 72. The TCM 17 is operatively connected to the electro-hydraulic
control circuit 42, including for monitoring various pressure sensing devices
(not shown) and generating and executing control signals for various solenoids
to control pressure switches and control valves contained therein.
[0019] The ECM 23 is operably connected to the engine 14, and functions to
acquire data from a variety of sensors and control a variety of actuators,
respectively, of the engine 14 over a plurality of discrete lines collectively
shown as aggregate line 35. The ECM 23 receives the engine input torque
command from the HCP 5, and generates a desired axle torque, and an
indication of actual engine input torque, T,, to the transmission, which is

communicated to the HCP 5. For simplicity, ECM 23 is shown generally
having bi-directional interface with engine 14 via aggregate line 35. Various
other parameters that may be sensed by ECM 23 include engine coolant
temperature, engine input speed, NE, to shaft 12 (which translate to
transmission input speed, NI) manifold pressure, ambient air temperature, and
ambient pressure. Various actuators that may be controlled by the ECM 23
include fuel injectors, ignition modules, and throttle control modules.
[0020] The TCM 17 is operably connected to the transmission 10 and
functions to acquire data from a variety of sensors and provide command
signals to the transmission. Inputs from the TCM ] 7 to the HCP 5 include
estimated clutch torques (TCL_N) for each of the N clutches, i.e., C1, C2, C3,
and C4, and rotational output speed, No, of the output shaft 64. Other
actuators and sensors may be used to provide additional information from the
TCM to the HCP for control purposes. The TCM 17 monitors inputs from
pressure switches and selectively actuates pressure control solenoids and shift
solenoids to actuate various clutches to achieve various transmission operating
modes, as described hereinbelow.
[0021] The BPCM 21 is signally connected one or more sensors operable to
monitor electrical current or voltage parameters of the ESD 74 to provide
information about the state of the batteries to the HCP 5. Such information
includes battery state-of-charge, amp-hour throughput, battery temperature,
battery voltage and available battery power.
[0022] Each of the aforementioned control modules is preferably a general-
purpose digital computer generally comprising a microprocessor or central
processing unit, storage mediums comprising read only memory (ROM),
random access memory (RAM), electrically programmable read only memory
(EPROM), high speed clock, analog to digital (A/D) and digital to analog
(D/A) circuitry, and input/output circuitry and devices (I/O) and appropriate
signal conditioning and buffer circuitry. Each control module has a set of
control algorithms, comprising resident program instructions and calibrations

stored in ROM and executed to provide the respective functions of each
computer. Information transfer between the various computers is preferably
accomplished using the aforementioned LAN 6.
[0023] Algorithms for control and state estimation in each of the control
modules are typically executed during preset loop cycles such that each
algorithm is executed at least once each loop cycle. Algorithms stored in the
non-volatile memory devices are executed by one of the central processing
units and are operable to monitor inputs from the sensing devices and execute
control and diagnostic routines to control operation of the respective device,
using preset calibrations. Loop cycles are typically executed at regular
intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during
ongoing engine and vehicle operation. Alternatively, algorithms may be
executed in response to occurrence of an event.
[0024] Referring now to Fig. 3, the exemplary two-mode, compound-split,
electro-mechanical transmission operates in one of several operating range
states comprising fixed gear operation and continuously variable operation,
described with reference to Table 1, below.

[0025] The various transmission operating range states described in the table
indicate which of the specific clutches Cl, C2, C3, and CA are engaged or
actuated for each of the operating range states. A first continuously variable
operating range state, i.e., Mode I, is selected when clutch Cl 70 is actuated in
order to "ground" the outer gear member of the third planetary gear set 28. The
engine 14 can be either on or off. A second continuously variable operating
range state, i.e., Mode II, is selected when clutch C1 70 is released and clutch
C2 62 is simultaneously actuated to connect the shaft 60 to the carrier of the
third planetary gear set 28. Again, the engine 14 can be either on or off. For
purposes of this description, Engine Off is defined by engine input speed, NE,
being equal to zero revolutions per minute (RPM), i.e., the engine crankshaft
is not rotating, typically as a result of the engine being decoupled from the
transmission. Other factors outside the scope of this disclosure affect when
the electric machines 56, 72 operate as motors and generators, and are not
discussed herein.
[0026] Mode I and Mode II are characterized by single clutch applications,
i.e., either clutch Cl 62 or C2 70, and by the controlled speed and torque of
the electric machines 56 and 72, which can be referred to as a continuously
variable transmission mode. Certain operating rage states are described below
in which fixed gear ratios are achieved by applying an additional clutch. This
additional clutch may be clutch C3 73 or C4 75, as shown in the table, above.
When the additional clutch is applied, fixed gear operation of input-to-output
speed of the transmission, i.e., NI/No, is achieved. During fixed gear
operation, the rotations of machines MG-A 56 and MG-B 72, i.e., NA and NB,
are dependent on internal rotation of the mechanism as defined by the
clutching and proportional to the input speed measured at shaft 12.
[0027] In response to an operator's action, as captured by the UI 13, the
supervisory HCP control module 5 and one or more of the other control
modules determine the operator torque request to be executed at shaft 64.
Final vehicle acceleration is affected by other factors, including, e.g., road

load, road grade, and vehicle mass. The transmission operating range state is
determined for the exemplary transmission based upon a variety of operating
characteristics of the powertrain. This includes an operator demand for
torque, typically communicated through inputs to the UI 13 as previously
described. Additionally, a demand for output torque is predicated on external
conditions, including, e.g., road grade, road surface conditions, or wind load.
The transmission operating range state may be predicated on a powertrain
torque demand caused by a control module command to operate one of the
electric machines as an electrical generator or as an electric motor. The
transmission operating range state can be determined by an optimization
algorithm or routine operable to determine optimum system efficiency based
upon operator demand for power, battery state of charge, and energy
efficiencies of the engine 14 and MG-A 56 and MG-B 72. The control system
manages torque inputs from the engine 14 and MG-A 56 and MG-B 72 based
upon an outcome of the executed optimization routine, and system
optimization occurs to optimize system efficiencies to improve fuel economy
and manage battery charging. Furthermore, operation can be determined
based upon a fault in a component or system. The HCP 5 monitors the
parametric states of the torque-generative devices, and determines the output
of the transmission required to arrive at the desired torque output, as described
hereinbelow. Under the direction of the HCP 5, the transmission 10 operates
over a range of output speeds from slow to fast in order to meet the operator
demand.
[0028] The energy storage system and electric machines MG-A 56 and MG-
B 72 are electrically-operatively coupled for power flow therebetween.
Furthermore, the engine, the electric machines, and the electro-mechanical
transmission are mechanically-operatively coupled to transmit power
therebetween to generate a power flow to the output. In Mode I operation, the
transmission operates as an input-split electrically variable transmission
(EVT). In Mode II operation, the transmission operates as a compound-split

EVT. While operating in either of these two modes, the control system
performs closed loop control on an engine speed which optimizes fuel
economy while still meeting the torque request and given power constraints.
It then commands motor speeds to vary the input-to-output speed ratio to
accelerate the vehicle, in response to the operator torque request. Through use
of the two additional clutches, the transmission also has the capability of
achieving one of four fixed gear ratios. While operating in a fixed gear, the
vehicle acts as a parallel hybrid and the motors are used only for boosting and
braking/regeneration the vehicle.
[0029] Referring to Fig. 4, a schematic diagram is depicted which provides a
more detailed description of the exemplary electro-hydraulic system for
controlling flow of hydraulic fluid in the exemplary transmission. The main
hydraulic pump 88, driven off the input shaft 12 from the engine 14, and
auxiliary pump 110, operatively electrically controlled by the TPIM 19,
provides pressurized fluid to the hydraulic circuit 42 through valve 140. The
auxiliary pump 110 preferably comprises an electrically-powered pump of an
appropriate size and capacity to provide sufficient flow of pressurized
hydraulic fluid into the hydraulic system when operational. Pressurized
hydraulic fluid flows into electro-hydraulic control circuit 42, which is
operable to selectively distribute hydraulic pressure to a series of devices,
including the torque-transfer clutches C\ 70, C2 62, C3 73, and C4 75, active
cooling circuits for machines A and B, and a base cooling circuit for cooling
and lubricating the transmission 10 via passages 142, 144 (not depicted in
detail). As previously stated, the TCM 17 is preferably operable to actuate the
various clutches to achieve various transmission operation through selective
actuation of hydraulic circuit flow control devices comprising variable
pressure control solenoids (PCS) PCS1 108, PCS2 112, PCS3 114, PCS4 116
and solenoid-controlled flow management valves X-valve 119 and Y-valve
121. The circuit is fluidly connected to pressure switches PS1, PS2, PS3, and
PS4 via passages 124, 122, 126, and 128, respectively. There is an inlet spool

valve 107. The pressure control solenoid PCS1 108 has a control position of
normally high and is operative to modulate fluidic pressure in the hydraulic
circuit through fluidic interaction with controllable pressure regulator 109.
Controllable pressure regulator 109, not shown in detail, interacts with PCS1
108 to control hydraulic pressure in the hydraulic circuit 42 over a range of
pressures, depending upon operating conditions as described hereinafter.
Pressure control solenoid PCS2 112 has a control position of normally low,
and is fluidly connected to spool valve 113 and operative to effect flow
therethrough when actuated. Spool valve 113 is fluidly connected to pressure
switch PS3 via passage 126. Pressure control solenoid PCS3 114 has a control
position of normally low, and is fluidly connected to spool valve 115 and
operative to effect flow therethrough when actuated. Spool valve 115 is
fluidly connected to pressure switch PS1 via passage 124. Pressure control
solenoid PCS4 116 has a control position of normally low, and is fluidly
connected to spool valve 117 and operative to effect flow therethrough when
actuated. Spool valve 117 is fluidly connected to pressure switch PS4 via
passage 128.
[0030] The X-Valve 119 and Y-Valve 121 each comprise flow management
valves controlled by solenoids 118, 120, respectively, in the exemplary
system, and have control states of High (1) and Low (0). The control states
refer to positions of each valve with which to control flow to different devices
in the hydraulic circuit 42 and the transmission 10. The X-valve 119 is
operative to direct pressurized fluid to clutches C3 and C4 and cooling
systems for stators of MG-A 56 and MG-B 72 via fluidic passages 136, 138,
144, 142 respectively, depending upon the source of the fluidic input, as is
described hereinafter. The Y-valve 121 is operative to direct pressurized fluid
to clutches Cl and C2 via fluidic passages 132 and 134 respectively,
depending upon the source of the fluidic input, as is described hereinafter.
The Y-valve 121 is fluidly connected to pressure switch PS2 via passage 122.
A more detailed description of the exemplary electro-hydraulic control circuit

42 is provided in commonly assigned U.S. Patent Application No. 11/263,216,
which is incorporated herein by reference.
[0031] An exemplary logic table to accomplish control of the exemplary
electro-hydraulic control circuit 42 is provided with reference to Table 2,
below.

[0032] Selective control of the X and Y valves and actuation of the solenoids
PCS2, PCS3, and PCS4 facilitate flow of hydraulic fluid to actuate clutches
C1, C2, C3, and C4, and provide cooling for the stators of MG-A 56 and MG-
B 72.

[0033] In operation, one of the fixed gear and continuously variable
operating range states is determined for the exemplary transmission based
upon a variety of operating characteristics of the powertrain. This includes an
operator torque request, typically communicated through inputs to the UI 13 as
previously described. Additionally, a demand for output torque is predicated
on external conditions, including, e.g., road grade, road surface conditions, or
wind load. Transmission operating range state may be predicated on a
powertrain torque demand caused by a control module command to operate of
the electric machines as an electrical generator or as an electrical motor.
Operation can be determined by an optimization algorithm or routine operable
to determine optimum system efficiency based upon operator demand for
power, battery state of charge, and energy efficiencies of the engine 14 and
MG-A 56 and MG-B 72. The control system manages torque inputs from the
engine 14 and MG-A 56 and MG-B 72 based upon an outcome of the executed
optimization routine, and system optimization occurs to optimize system
efficiencies to improve fuel economy and manage battery charging.
Furthermore, operation can be determined based upon a fault in a component
or system.
[0034] Referring now to the transmission described with reference to Figs. 1,
2, 3, and 4, and Tables 1 and 2, specific aspects of the transmission and
control system are described herein. The control system is operative to
selectively actuate the pressure control devices and the flow management
valves based upon a demand for torque, presence of a fault, and temperatures
of the electric motors. The control system selectively commands one of a low-
range continuously variable operation, a high-range continuously variable
operation, a low range state, and a high range state based upon selective
actuation of the X-valve 118 and Y-valve 120 flow management valves. The
control system effects actuation of the stator cooling system for the first
electric machine (MG-A Stator Cool), the stator cooling system for the second
electric machine (MG-B Stator Cool), and the first hydraulically-actuated

clutch (C1) based upon selective actuation of the pressure control devices
PCS2, PCS3, and PCS4 when the low-range continuously variable operation
has been commanded. Furthermore, the control system is operative to effect
actuation of the stator cooling system for MG-A 56, stator cooling system for
MG-B 72, and the second hydraulically-actuated clutch C2 based upon
selective actuation of the pressure control devices when a high-range
continuously variable operation has been commanded. The control system is
operative to effect actuation of the first, second, and fourth hydraulically-
actuated clutches (i.e., C1, C2, C4) based upon selective actuation of the
pressure control devices when a low-range state has been commanded,
comprising operation in one of FG1, FG2, Mode I via selective actuation of
the clutches. The control system is operative to effect actuation of the second,
third, and fourth hydraulically-actuated clutches (i.e., C2, C3, C4) based upon
selective actuation of the pressure control devices when a high-range state has
been commanded, comprising operation in one of FG3, FG4, and Mode II via
selective actuation of the clutches.
[0035] As previously stated, fluid output from each of the second, third and
fourth pressure control devices (i.e., PCS2, PCS3, and PCS4) is selectively
mapped to one of the four hydraulically-actuated clutches and stator cooling
systems for MG-A 56 and MG-B 72 based upon commanded positions of the
first and second flow management valves. Therefore, selective actuation of
PCS2 effects flow of hydraulic fluid to provide cooling to the stator of MG-B
72, when both the X-valve and the Y-valve are commanded to Low. Selective
actuation of PCS2 effects flow of hydraulic fluid to actuate clutch C2 when
either of the X-valve and the Y-valve are commanded to High. Selective
actuation of PCS3 effects flow of hydraulic fluid to actuate clutch Cl when
both the X-valve and the Y-valve are commanded to Low. Selective actuation
of PCS3 effects flow of hydraulic fluid to provide cooling to the stator of MG-
B 72 when the X-valve is commanded to Low and the Y-valve is commanded
to High. Selective actuation of PCS3 effects flow of hydraulic fluid to actuate

clutch Cl when the X-valve is commanded to High and the Y-valve is
commanded to Low. Selective actuation of PCS3 effects flow of hydraulic
fluid to actuate clutch C3 when both the X-valve and the Y-valve are
commanded to High. Selective actuation of PCS4 effects flow of hydraulic
fluid to provide cooling to the stator of MG-A 56 when the X-valve is
commanded to Low, regardless of the position to which the Y-valve is
commanded. Selective actuation of PCS4 effects flow of hydraulic fluid to
actuate clutch C4 when the X-valve is commanded to High, regardless of the
position to which the Y-valve is commanded.
[0036] Referring now to the flowchart 400 depicted in Fig. 5, with reference
to the exemplary transmission described with reference to Figs. 1, 2, 3, and 4,
and Tables 1 and 2, specific aspects of controlling operation of the exemplary
transmission and control system are described. In operation, the electro-
mechanical transmission is commanded by one of the control modules to
operate in one of the continuously variable operating range states (Step 410),
i.e., either Mode I or II, through selective actuation of either clutch C1 or
clutch C2. Operation of the transmission is monitored, including the rotational
speeds of various elements, including specifically transmission speeds No, NA,
and NB (Step 412). Other elements are monitored, as required for operation of
the system, e.g., NE, TA, and TB. An absence of a mismatch between the
commanded operating range state and the actual operating state of the
transmission is determined based upon the monitored operation of the
transmission (Step 414). Presence of a mismatch between the commanded
operating range state and the actual operating state of the transmission is
detected based upon the monitored operation of the transmission, including
presence of excess motor torque and clutch slippage (Steps 416, 418). The
commanded operation of the internal combustion engine is modified when a
mismatch between the commanded operating range state and an actual
operating state of the transmission is detected (Step 420). This is now
described in detail.

[0037] A potential powertrain system fault includes a mismatch between a
commanded operating range state and an actual operating state of the
transmission. This includes the control system commanding operation in one
of the continuously variable operating range states, whereas the transmission
actually operates in one of the fixed gear operating range states. This is
referred to as a mode-gear mismatch. During ongoing operation, the control
system commands either of continuously variable operating range states,
Mode 1 and Mode II, as depicted in Table 2. In each Mode operation only one
clutch is applied for the exemplary embodiment, which corresponds to one
pressure control solenoid (PCS) in the hydraulically high state. The hydraulic
system is designed such that if a hardware fault occurs affecting either of the
remaining two pressure control solenoids while operating in either Mode I or
Mode II, the only result is motor stator cooling.
[0038] It can be seen that in both Mode I or Mode II, the X-valve 119 is in a
hydraulically low state. If there is a fault in the X-valve causing it to remain
in a hydraulically high state, a single fault in one of the PCS devices can lead
to an unacceptable operating condition. For example, were the X valve to
have a fault causing it to remain 'HIGH', the vehicle continues to operate in
Mode I by operating in the 'Low Range' state and commanding PCS3
hydraulically high. However, any subsequent fault on PCS2 in HIGH position
may result in application of clutch C2, with a corresponding mismatch, in that
Mode I is commanded, whereas FG2 is executed in the transmission.
[0039] A first tactic for detecting a mode-gear mismatch includes
affirmatively determining an absence of any mode-gear mismatch by
monitoring clutch slippage. This detection tactic comprises monitoring and
detecting clutch slippage during steady state operation in one of Mode I and II,
wherein only a single clutch is applied, i.e., commanded actuated. During
operation, only a single clutch, i.e., either C1 or C2, is expected to
demonstrate clutch slippage at or near-zero during any given period of time.
When there is a significant amount of slip across a clutch for a period of time

it can be determined that the specific clutch is not actuated, and there is no
mode-gear mismatch. Thus, in Mode I, Clutch C1 is commanded actuated,
with slippage occurring across each of clutches C2, C3, and C4. Thus, in
Mode II, Clutch C2 is commanded actuated, with slippage occurring across
each of clutches C1, C3, and C4. When such slippage conditions are
determined for the clutches whose actuation is not commanded, the control
strategy affirms the absence of a mode-gear mismatch. However, if a
condition occurs wherein it is determined that one of the unactuated clutches
has slippage at or near zero slip speed for more than a minimal amount of
time, then there is a potential that the clutch is actuated, and a potential for a
mode-gear mismatch. Slippage across each of the clutches is determined
based upon the various measured rotational speeds of NE, No, NA, and NB.
[0040] A second tactic for detecting a mode-gear mismatch includes
affirmatively determining an absence of a mode-gear mismatch by monitoring
engine input speed. During operation in Mode I or Mode II, the control
system controls input speed, NI, to a calculated optimum engine speed,
Ni_opt. In closed loop control around the optimum input speed, Niopt, the
input speed is expected to follow an optimum speed profile, determined based
upon operating conditions and operator inputs. In the system described
hereinabove, the relationship between various speeds is fixed by the hardware,
comprising (NA + NB)/2 = NI. In this tactic, the motor speeds NA and NB are
measured with the resolvers 80, 82, and input speed, NI, is calculated
therefrom. In the event of a mode-gear mismatch, it is likely that there is a
significant difference between the current engine speed, NI, and the optimum
input speed, Niopt, which is determined as a part of the engine and system
operation. Therefore, when the input speed, NI, follows the optimum input
speed, Niopt, the control strategy affirms the absence of a mode-gear
mismatch, and when there is a difference in the input speed and the optimum
input speed, there is potentially a mode-gear mismatch.

[0041] When the outcomes of the first and second tactics are unable to
affirm the absence of a mode-gear mismatch, additional tactics are executed to
detect the presence of a mode-gear mismatch. For example, during steady
state operation a mode-gear mismatch may occur which is unperceivable to
the vehicle operator, or results in a light acceleration event. A third tactic for
detecting a mode-gear mismatch includes affirmatively detecting presence of
the mode-gear mismatch by monitoring motor torque from both of the electric
machines. During operation in either Mode I or Mode II, the control system
calculates the motor torque needed from both the electric machines to achieve
the optimum closed loop engine speed control, Niopt. The current motor
torques from the machines are determined based upon electric power
transferred thereto. Excess torque for each motor, based upon a difference
between the current motor torque and calculated motor torque, is calculated.
A calculation indicating a significant amount of excess torque being applied
by one of the electric machines to one of the clutches indicates presence of a
mode-gear mismatch.
[0042] A fourth tactic for detecting a mode-gear mismatch includes
affirmatively detecting presence of the mode-gear mismatch by monitoring
slippage of the clutches to detect zero-slip conditions. During operation in
either Mode I or Mode II, a clutch which is not actuated is expected to have
slippage. By monitoring clutch slippage, a zero-slip condition can be
determined. When the output speed is not decelerating, then slip speed of an
oncoming clutch eventually reaches near-zero speed (steady state), even
during a mode-gear mismatch. Therefore, when there is no clutch slippage in
an unapplied clutch, the control strategy is able to detect a mode-gear
mismatch.

[0043] When a mode-gear mismatch is experienced and detected, operation
of the powertrain is preferably modified in a timely manner. Modifying
powertrain operation includes disabling the closed loop engine speed control,
to prevent the control system from varying the engine input speed, preferably
within 200 msec of the detection. This includes sending a software control
flag to the control system to disable the closed loop engine control, and
subsequently informing the operator by illuminating a dashboard lamp. When
affirmative pass is subsequently detected, i.e., an outcome of executing the
first or second tactics results in a pass condition for a calibratable length of
time, the closed loop engine control is preferably re-enabled.
[0044] There are preferably different conditions for affirmatively
determining an absence of the mode-gear mismatch, and affirmatively
determining a presence of a mode-gear mismatch. Therefore, there can be a
condition wherein a vehicle may both determine an absence and determine a
presence of a mode-gear mismatch at the same time. This may occur during a
short time window when the vehicle is experiencing a sharp deceleration due
to an oncoming clutch which still has a slip speed above the threshold of the
pass criteria. For this reason the action of disabling the closed loop speed
control continues until the pass condition has been met for a calibratable
amount of time, typically less than four seconds. If the clutch continues to be
applied, the clutch slip speed drops below the pass condition threshold within
the calibratable amount of time and engine closed loop remains disabled. If
the clutch is no longer applied, and the test continues to pass, engine closed
loop control is re-enabled.
[0045] The invention has been described with specific reference to the
disclosed embodiments and modifications thereto. Further modifications and
alterations may occur to others upon reading and understanding the
specification. It is intended to include all such modifications and alterations
insofar as they come within the scope of the invention.

Having thus described the invention, it is claimed:
1. Method for operating a powertrain including an electro-mechanical
transmission mechanically-operatively coupled to an internal combustion
engine and a pair of electric machines for mechanical power flow to an output
through selective actuation of a plurality of torque-transfer clutches, said
electric machines electrically-operatively coupled to an energy storage system
for electric power flow therebetween, the method comprising:
commanding operation of the electro-mechanical transmission in a
continuously variable operating range state;
monitoring operation of the transmission;
determining absence of a mismatch between the commanded continuously
variable operating range state and an actual operating state of the
transmission;
detecting presence of a mismatch between the commanded continuously
variable operating range state and the actual operating state of the
transmission; and,
modifying operation of the powertrain when a mismatch between the
commanded continuously variable operating range state and the actual
operating state of the transmission is detected.
2. The method of claim 1, wherein commanding operation of the electro-
mechanical transmission in a continuously variable operating range state
comprises selectively actuating a single one of the torque-transfer clutches.
3. The method of claim 2, wherein monitoring operation of the
transmission comprises monitoring rotational speeds of inputs and an output of
the transmission and monitoring torque output from the electric machines.

4. The method of claim 3, wherein determining the absence of a
mismatch between the commanded continuously variable operating range state
and the actual operating state of the transmission comprises:
determining slippage across each of the clutches based upon the monitored
rotational speeds of the inputs and the output of the transmission and
the electric machines; and,
determining clutch slippage is greater than zero for each of the torque transfer
clutches not selectively actuated.
5. The method of claim 4, wherein determining absence of a mismatch
between the commanded continuously variable operating range state and the
actual operating state of the transmission further comprises:
determining an optimum input speed, and,
determining the input speed is substantially close to the optimum input speed.
6. The method of claim 5, wherein detecting a presence of a mismatch
between the commanded continuously variable operating range state and the
actual operating state of the transmission further comprises:
calculating motor torque from the electric machines to achieve the optimum
input speed; and,
determining application of excess torque to one of the clutches.
7. The method of claim 6, wherein detecting the presence of a mismatch
between the commanded continuously variable operating range state and the
actual operating state of the transmission comprises determining clutch
slippage is substantially near zero for only the selectively actuated single one
of the torque-transfer clutches.

8. The method of claim 1, wherein determining absence of a mismatch
between the commanded continuously variable operating range state and the
actual operating state of the transmission comprises:
determining an optimum input speed, and,
determining the input speed is substantially close to the optimum input speed.
9. The method of claim 1, wherein determining absence of a mismatch
between the commanded continuously variable operating range state and the
actual operating state of the transmission comprises:
determining slippage across each of the clutches based upon monitored
rotational speeds of an input and an output of the transmission and the
electric machines; and,
determining clutch slippage is greater than zero for each of the torque transfer
clutches not selectively actuated.
10. The method of claim 1, wherein determining the absence of a
mismatch between the commanded continuously variable operating range state
and the actual operating state of the transmission comprises:
determining slippage across each of the clutches based upon monitored
rotational speeds of an input and an output of the transmission and the
electric machines;
determining clutch slippage is greater than zero for each of the torque transfer
clutches not selectively actuated; and,
determining clutch slippage is substantially zero for only the selectively
actuated single one of the torque-transfer clutches.
11. The method of claim 1, wherein modifying operation of the powertrain
when a mismatch between the commanded continuously variable operating
range state and an actual operating state of the transmission is detected
comprises modifying a commanded operation of the internal combustion
engine.

12. Method for operating a powertrain including an electro-mechanical
transmission mechanically-operatively coupled to an internal combustion
engine and a pair of electric machines for mechanical power flow to an output
through selective actuation of a plurality of torque-transfer clutches, said
electric machines electrically-operatively coupled to an energy storage system
for electric power flow therebetween, the method comprising:
commanding operation of the electro-mechanical transmission in a
continuously variable operating range state;
controlling the internal combustion engine in closed loop engine speed control
based upon an optimum engine speed;
monitoring operation of the transmission;
determining absence of a mismatch between the commanded operation of the
electro-mechanical transmission and an actual operation of the electro-
mechanical transmission;
detecting presence of a mismatch between the commanded operation of the
electro-mechanical transmission and the actual operation of the electro-
mechanical transmission; and,
disabling the closed loop engine speed control when a mismatch between the
commanded operation of the electro-mechanical transmission and the
actual operation of the electro-mechanical transmission is detected.
13. The method of claim 12, further comprising re-enabling the closed
loop engine speed control when the detected mismatch between the
commanded operation of the electro-mechanical transmission and the actual
operation of the electro-mechanical transmission is subsequently determined
absent.

14. Method for operating a powertrain including an electro-mechanical
transmission mechanically-operatively coupled to an internal combustion
engine and a pair of electric machines for mechanical power flow to an output
through selective actuation of a plurality of torque-transfer clutches, said
electric machines electrically-operatively coupled to an energy storage system
for electric power flow therebetween, the method comprising:
selectively commanding actuation of a single one of the torque transfer
clutches;
determining absence of a mismatch between the commanded actuation of the
single one of the torque transfer clutches and an actual operating state
of the transmission;
detecting presence of a mismatch between the commanded actuation of the
single one of the torque transfer clutches and the actual operating state
of the transmission; and,
modifying operation of the powertrain when a mismatch between the
commanded actuation of the single one of the torque transfer clutches
and the actual operating state of the transmission is detected.
15. The method of claim 14, wherein the determining absence of a
mismatch between the commanded actuation of the single one of the torque
transfer clutches and the actual operating state of the transmission comprises:
determining slippage across each of the clutches based upon monitored
rotational speeds of transmission inputs and the transmission and the
electric machines; and,
determining clutch slippage is greater than zero for each of the torque transfer
clutches not selectively actuated.

16. The method of claim 14, wherein determining absence of a mismatch
between the commanded actuation of the single one of the torque transfer
clutches and the actual operating state of the transmission further comprises:
determining an optimum input speed to the transmission, and,
determining the input speed is substantially close to the optimum input speed
to the transmission.
17. The method of claim 14, wherein detecting presence of a mismatch
between the commanded actuation of the single one of the torque transfer
clutches and the actual operating state of the transmission further comprises:
calculating motor torque from the electric machines to achieve the optimum
engine speed; and,
determining application of excess torque to any one of the clutches.
18. The method of claim 14, wherein detecting presence of a mismatch
between the commanded actuation of the single one of the torque transfer
clutches and the actual operating state of the transmission comprises
determining clutch slippage is substantially zero for only the selectively
actuated single one of the torque-transfer clutches.

Control of operation of a hybrid powertrain is provided, wherein mechanical power flow to an output is controlled through selective actuation
of torque-transfer clutches. Electric machines are coupled to an energy storage system for electric power flow. The electro-mechanical transmission is operated in a continuously variable operating range state, and, operation of
the transmission is monitored. Absence of a mismatch between the commanded continuously variable operating range state and an actual
operating state of the transmission is determined. Presence of a mismatch between the commanded operating range state and the actual operating state of the transmission may be determined. Operation of the powertrain is modified when a mismatch between the commanded operating range state and the actual operating state of the transmission is detected.

Documents:

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Patent Number

268603

Indian Patent Application Number

1713/KOL/2008

PG Journal Number

37/2015

Publication Date

11-Sep-2015

Grant Date

07-Sep-2015

Date of Filing

03-Oct-2008

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS INC.

Applicant Address

300 RENAISSANCE CENTER, DETROIT, MICHIGAN

Inventors:

#	Inventor's Name	Inventor's Address
1	CHARLES J VAN HORN	47218 MANHATTAN CIRCLE NOVI, MICHIGAN, 48374
2	RYAN D. MARTINI	412 E. KENIL WORTH AVENUE ROYAL OAK, MICHIGAN 48067
3	ANDREW M. ZETTEL	1839 MICHELLE COURT, ANN ARBOR, MICHIGAN 48105
4	OSAMA ALMASRI	39738 VILLAGE WOODE CIRCLE, NOVI, MICHIGAN 48375
5	JY-JEN F. SAH	1915 BLOOMFIELD, MICHIGAN OAKS DRIVE, WEST BLOOMFIELD, MICHIGAN 48324
6	SAM ALMASRI	39738 VILLAGE WOODE CIRCLE NOVI, MICHIGAN 48375
7	PETER E. WU	5230 RED FOX DRIVE, BRIGHTON, MICHIGAN 48114

PCT International Classification Number

F16H37/06; G06F11/00; F16H37/06; G06F11/

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	11/866100	2007-10-02	U.S.A.