Title of Invention	A METHOD FOR CONTROLLING AN ELECTRO-MECHANICAL TRANSMISSION MECHANICALLY COUPLED TO FIRST AND SECOND ELECTRIC MACHINES TO TRANSMIT POWER TO AN OUTPUT MEMBER BY DETERMINING MOTOR TORQUE CONSTRAINTS AND BATTERY POWER CONSTRAINTS
Abstract	A method for controlling an electro-mechanical transmission mechanically coupled to first and second electric machines to transmit power to an output member includes determining motor torque constraints and battery power constraints. A preferred output torque to an output member is determined that is achievable within the motor torque constraints, within a range for an additional torque input and based upon the battery power constraints.

Title of Invention

A METHOD FOR CONTROLLING AN ELECTRO-MECHANICAL TRANSMISSION MECHANICALLY COUPLED TO FIRST AND SECOND ELECTRIC MACHINES TO TRANSMIT POWER TO AN OUTPUT MEMBER BY DETERMINING MOTOR TORQUE CONSTRAINTS AND BATTERY POWER CONSTRAINTS

Abstract

A method for controlling an electro-mechanical transmission mechanically coupled to first and second electric machines to transmit power to an output member includes determining motor torque constraints and battery power constraints. A preferred output torque to an output member is determined that is achievable within the motor torque constraints, within a range for an additional torque input and based upon the battery power constraints.

Full Text	SYSTEM CONSTRAINTS METHOD OF CONTROLLING OPERATION OF AN ELECTRO-MECHANICAL TRANSMISSION WITH AN ADDITIONAL CONSTRAINT RANGE CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/984,492 filed on 11/01/2007 which is hereby incorporated herein by reference. TECHNICAL FIELD [0002] This disclosure pertains to control systems for electro-mechanical transmissions. BACKGROUND [0003] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. [0004] Known hybrid powertrain architectures can include multiple torque-generative devices, including internal combustion engines and non- combustion machines, e.g., electric machines, which transmit torque through a transmission device to an output member. One exemplary hybrid powertrain includes a two-mode, compound-split, electro-mechanical transmission which utilizes an input member for receiving tractive torque from a prime mover power source, preferably an internal combustion engine, and an output member. The output member can be operatively connected to a driveline for a motor vehicle for transmitting tractive torque thereto. Machines, operative as motors or generators, can generate torque inputs to the transmission independently of a torque input from the internal combustion engine. The machines may transform vehicle kinetic energy transmitted through the vehicle driveline to energy that is storable in an energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling transmission operating state and gear shifting, controlling the torque- generative devices, and regulating the power interchange among the energy storage device and the machines to manage outputs of the transmission, including torque and rotational speed. SUMMARY [0005] A powertrain includes an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and first and second electric machines to transmit power to an output member. A method for controlling the electro-mechanical transmission includes determining motor torque constraints for the first and second electric machines, and determining battery power constraints for an electrical energy storage device. A range for an additional torque input to the electro- mechanical transmission is determined. A preferred output torque to the output member of the electro-mechanical transmission is determined that is achievable within the motor torque constraints and within the range of the additional torque input and is based upon the battery power constraints. BRIEF DESCRIPTION OF THE DRAWINGS [0006] One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: [0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in accordance with the present disclosure; [0008] Fig. 2 is a schematic diagram of an exemplary architecture for a control system and powertrain, in accordance with the present disclosure; [0009] Figs. 3-4 are graphical diagrams, in accordance with the present disclosure; and [0010] Fig. 5 is an algorithmic flowchart, in accordance with the present disclosure. DETAILED DESCRIPTION [0011] Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, Figs. 1 and 2 depict an exemplary electro- mechanical hybrid powertrain. The exemplary electro-mechanical hybrid powertrain in accordance with the present disclosure is depicted in Fig. 1, comprising a two-mode, compound-split, electro-mechanical hybrid transmission 10 operatively connected to an engine 14 and first and second electric machines ('MG-A') 56 and ('MG-B') 72. The engine 14 and first and second electric machines 56 and 72 each generate power which can be transferred to the transmission 10. The power generated by the engine 14 and the first and second electric machines 56 and 72 and transferred to the transmission 10 is described in terms of input and motor torques, referred to herein as TI, TA, and TB respectively, and speed, referred to herein as NI, NA, and NB, respectively. [0012] The exemplary engine 14 comprises a multi-cylinder internal combustion engine selectively operative in several states to transfer torque to the transmission 10 via an input shaft 12, and can be either a spark-ignition or a compression-ignition engine. The engine 14 includes a crankshaft (not shown) operatively coupled to the input shaft 12 of the transmission 10. A rotational speed sensor 11 monitors rotational speed of the input shaft 12. Power output from the engine 14, comprising rotational speed and engine torque, can differ from the input speed NI and the input torque TI to the transmission 10 due to placement of torque-consuming components on the input shaft 12 between the engine 14 and the transmission 10, e.g., a hydraulic pump (not shown) and/or a torque management device (not shown). [0013] The exemplary transmission 10 comprises three planetary-gear sets 24, 26 and 28, and four selectively engageable torque-transferring devices, i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutches refer to any type of friction torque transfer device including single or compound plate clutches or packs, band clutches, and brakes, for example. A hydraulic control circuit 42, preferably controlled by a transmission control module (hereafter 'TCM') 17, is operative to control clutch states. Clutches C2 62 and C4 75 preferably comprise hydraulically-applied rotating friction clutches. Clutches C1 70 and C3 73 preferably comprise hydraulically-controlled stationary devices that can be selectively grounded to a transmission case 68. Each of the clutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulically applied, selectively receiving pressurized hydraulic fluid via the hydraulic control circuit 42. [0014] The first and second electric machines 56 and 72 preferably comprise three-phase AC machines, each including a stator (not shown) and a rotor (not shown), and respective resolvers 80 and 82. The motor stator for each machine is grounded to an outer portion of the transmission case 68, and includes a stator core with coiled electrical windings extending therefrom. The rotor for the first electric machine 56 is supported on a hub plate gear that is operatively attached to shaft 60 via the second planetary gear set 26. The rotor for the second electric machine 72 is fixedly attached to a sleeve shaft hub 66. [0015] Each of the resolvers 80 and 82 preferably comprises a variable reluctance device including a resolver stator (not shown) and a resolver rotor (not shown). The resolvers 80 and 82 are appropriately positioned and assembled on respective ones of the first and second electric machines 56 and 72. Stators of respective ones of the resolvers 80 and 82 are operatively connected to one of the stators for the first and second electric machines 56 and 72. The resolver rotors are operatively connected to the rotor for the corresponding first and second electric machines 56 and 72. Each of the resolvers 80 and 82 is signally and operatively connected to a transmission power inverter control module (hereafter 'TPIM') 19, and each senses and monitors rotational position of the resolver rotor relative to the resolver stator, thus monitoring rotational position of respective ones of first and second electric machines 56 and 72. Additionally, the signals output from the resolvers 80 and 82 are interpreted to provide the rotational speeds for first and second electric machines 56 and 72, i.e., NAand NB, respectively. [0016] The transmission 10 includes an output member 64, e.g. a shaft, which is operably connected to a driveline 90 for a vehicle (not shown), to provide output power to the driveline 90 that is transferred to vehicle wheels 93, one of which is shown in Fig. 1. The output power at the output member 64 is characterized in terms of an output rotational speed NO and an output torque TO. A transmission output speed sensor 84 monitors rotational speed and rotational direction of the output member 64. Each of the vehicle wheels 93 is preferably equipped with a sensor 94 adapted to monitor wheel speed, the output of which is monitored by a control module of a distributed control module system described with respect to Fig. 2, to determine vehicle speed, and absolute and relative wheel speeds for braking control, traction control, and vehicle acceleration management. [0017] The input torque from the engine 14 and the motor torques from the first and second electric machines 56 and 72 (TI, TA, and TB respectively) are generated as a result of energy conversion from fuel or electrical potential stored in an electrical energy storage device (hereafter 'ESD') 74. The ESD 74 is high voltage DC-coupled to the TPIM 19 via DC transfer conductors 27. The transfer conductors 27 include a contactor switch 38. When the contactor switch 38 is closed, under normal operation, electric current can flow between the ESD 74 and the TPIM 19. When the contactor switch 38 is opened electric current flow between the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmits electrical power to and from the first electric machine 56 by transfer conductors 29, and the TPIM 19 similarly transmits electrical power to and from the second electric machine 72 by transfer conductors 31 to meet the torque commands for the first and second electric machines 56 and 72 in response to the motor torques TA and TB. Electrical current is transmitted to and from the ESD 74 in accordance with whether the ESD 74 is being charged or discharged. [0018] The TPIM 19 includes the pair of power inverters (not shown) and respective motor control modules (not shown) configured to receive the torque commands and control inverter states therefrom for providing motor drive or regeneration functionality to meet the commanded motor torques TA and TB. The power inverters comprise known complementary three-phase power electronics devices, and each includes a plurality of insulated gate bipolar transistors (not shown) for converting DC power from the ESD 74 to AC power for powering respective ones of the first and second electric machines 56 and 72, by switching at high frequencies. The insulated gate bipolar transistors form a switch mode power supply configured to receive control commands. There is typically one pair of insulated gate bipolar transistors for each phase of each of the three-phase electric machines. States of the insulated gate bipolar transistors are controlled to provide motor drive mechanical power generation or electric power regeneration functionality. The three-phase inverters receive or supply DC electric power via DC transfer conductors 27 and transform it to or from three-phase AC power, which is conducted to or from the first and second electric machines 56 and 72 for operation as motors or generators via transfer conductors 29 and 31 respectively. [0019] Fig. 2 is a schematic block diagram of the distributed control module system. The elements described hereinafter comprise a subset of an overall vehicle control architecture, and provide coordinated system control of the exemplary hybrid powertrain described in Fig. 1. The distributed control module system synthesizes pertinent information and inputs, and executes algorithms to control various actuators to meet control objectives, including objectives related to fuel economy, emissions, performance, drivability, and protection of hardware, including batteries of ESD 74 and the first and second electric machines 56 and 72. The distributed control module system includes an engine control module (hereafter 'ECM') 23, the TCM 17, a battery pack control module (hereafter 'BPCM') 21, and the TPIM 19. A hybrid control module (hereafter 'HCP') 5 provides supervisory control and coordination of the ECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface ('UI') 13 is signally connected to a plurality of devices through which a vehicle operator controls or directs operation of the electro-mechanical hybrid powertrain. The devices include an accelerator pedal 113 ('AP'), an operator brake pedal 112 ('BP'), a transmission gear selector 114 ('PRNDL'), and a vehicle speed cruise control (not shown). The transmission gear selector 114 may have a discrete number of operator-selectable positions, including the rotational direction of the output member 64 to enable one of a forward and a reverse direction. [0020] The aforementioned control modules communicate with other control modules, sensors, and actuators via a local area network (hereafter 'LAN') bus 6. The LAN bus 6 allows for structured communication of states of operating parameters and actuator command signals between the various control modules. The specific communication protocol utilized is application- specific. The LAN bus 6 and appropriate protocols provide for robust messaging and multi-control module interfacing between the aforementioned control modules, and other control modules providing functionality including e.g., antilock braking, traction control, and vehicle stability. Multiple communications buses may be used to improve communications speed and provide some level of signal redundancy and integrity. Communication between individual control modules can also be effected using a direct link, e.g., a serial peripheral interface ('SPI') bus (not shown). [0021] The HCP 5 provides supervisory control of the hybrid powertrain, serving to coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21. Based upon various input signals from the user interface 13 and the hybrid powertrain, including the ESD 74, the HCP 5 determines an operator torque request, an output torque command, an engine input torque command, clutch torque(s) for the applied torque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, and the motor torques TA and TB for the first and second electric machines 56 and 72. The TCM 17 is operatively connected to the hydraulic control circuit 42 and provides various functions including monitoring various pressure sensing devices (not shown) and generating and communicating control signals to various solenoids (not shown) thereby controlling pressure switches and control valves contained within the hydraulic control circuit 42. [0022] The ECM 23 is operatively connected to the engine 14, and functions to acquire data from sensors and control actuators of the engine 14 over a plurality of discrete lines, shown for simplicity as an aggregate bi- directional interface cable 35. The ECM 23 receives the engine input torque command from the HCP 5. The ECM 23 determines the actual engine input torque, T\|, provided to the transmission 10 at that point in time based upon monitored engine speed and load, which is communicated to the HCP 5. The ECM 23 monitors input from the rotational speed sensor 11 to determine the engine input speed to the input shaft 12, which translates to the transmission input speed, N\. The ECM 23 monitors inputs from sensors (not shown) to determine states of other engine operating parameters including, e.g., a manifold pressure, engine coolant temperature, ambient air temperature, and ambient pressure. The engine load can be determined, for example, from the manifold pressure, or alternatively, from monitoring operator input to the accelerator pedal 113. The ECM 23 generates and communicates command signals to control engine actuators, including, e.g., fuel injectors, ignition modules, and throttle control modules, none of which are shown. [0023] The TCM 17 is operatively connected to the transmission 10 and monitors inputs from sensors (not shown) to determine states of transmission operating parameters. The TCM 17 generates and communicates command signals to control the transmission 10, including controlling the hydraulic circuit 42. Inputs from the TCM 17 to the HCP 5 include estimated clutch torques for each of the clutches, i.e., C1 70, C2 62, C3 73, and C4 75, and rotational output speed, NO, of the output member 64. Other actuators and sensors may be used to provide additional information from the TCM 17 to the HCP 5 for control purposes. The TCM 17 monitors inputs from pressure switches (not shown) and selectively actuates pressure control solenoids (not shown) and shift solenoids (not shown) of the hydraulic circuit 42 to selectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75 to achieve various transmission operating range states, as described hereinbelow. [0024] The BPCM 21 is signally connected to sensors (not shown) to monitor the ESD 74, including states of electrical current and voltage parameters, to provide information indicative of parametric states of the batteries of the ESD 74 to the HCP 5. The parametric states of the batteries preferably include battery state-of-charge, battery voltage, battery temperature, and available battery power, referred to as a range PBAT_MIN to PBAT_MAX. [0025] A brake control module (hereafter 'BrCM') 22 is operatively connected to friction brakes (not shown) on each of the vehicle wheels 93. The BrCM 22 monitors the operator input to the brake pedal 112 and generates control signals to control the friction brakes and sends a control signal to the HCP 5 to operate the first and second electric machines 56 and 72 based thereon. [0026] Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM 21, and BrCM 22 is preferably a general-purpose digital computer comprising a microprocessor or central processing unit, storage mediums comprising read only memory ('ROM'), random access memory ('RAM'), electrically programmable read only memory ('EPROM'), a 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 of the control modules has a set of control algorithms, comprising resident program instructions and calibrations stored in one of the storage mediums and executed to provide the respective functions of each computer. Information transfer between the control modules is preferably accomplished using the LAN bus 6 and serial peripheral interface buses. The control algorithms are 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 to monitor inputs from the sensing devices and execute control and diagnostic routines to control operation of the actuators, using preset calibrations. Loop cycles are executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing operation of the hybrid powertrain. Alternatively, algorithms may be executed in response to the occurrence of an event. [0027] The exemplary hybrid powertrain selectively operates in one of several operating range states that can be described in terms of an engine state comprising one of an engine-on state ('ON') and an engine-off state ('OFF'), and a transmission state comprising a plurality of fixed gears and continuously variable operating modes, described with reference to Table 1, below. Table 1 [0028] Each of the transmission operating range states is described in the table and indicates which of the specific clutches C1 70, C2 62, C3 73, and C4 75 are applied for each of the operating range states. A first continuously variable mode, i.e., EVT Mode 1, or Ml, is selected by applying clutch C1 70 only in order to "ground" the outer gear member of the third planetary gear set 28. The engine state can be one of ON ('M1_Eng_On') or OFF ('M1_Eng_Off). A second continuously variable mode, i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 only to connect the shaft 60 to the carrier of the third planetary gear set 28. The engine state can be one of ON ('M2_Eng_On') or OFF ('M2_Eng_Off). For purposes of this description, when the engine state is OFF, the engine input speed is equal to zero revolutions per minute ('RPM'), i.e., the engine crankshaft is not rotating. A fixed gear operation provides a fixed ratio operation of input-to-output speed of the transmission 10, i.e., NI/NO. A first fixed gear operation ('G1') is selected by applying clutches C1 70 and C4 75. A second fixed gear operation ('G2') is selected by applying clutches C1 70 and C2 62. A third fixed gear operation ('G3') is selected by applying clutches C2 62 and C4 75. A fourth fixed gear operation ('G4') is selected by applying clutches C2 62 and C3 73. The fixed ratio operation of input-to-output speed increases with increased fixed gear operation due to decreased gear ratios in the planetary gears 24, 26, and 28. The rotational speeds of the first and second electric machines 56 and 72, NAand NB respectively, are dependent on internal rotation of the mechanism as defined by the clutching and are proportional to the input speed measured at the input shaft 12. [0029] In response to operator input via the accelerator pedal 113 and brake pedal 112 as captured by the user interface 13, the HCP 5 and one or more of the other control modules determine torque commands to control the torque generative devices comprising the engine 14 and first and second electric machines 56 and 72 to meet the operator torque request at the output member 64 and transferred to the driveline 90. Based upon input signals from the user interface 13 and the hybrid powertrain including the ESD 74, the HCP 5 determines the operator torque request, a commanded output torque between the transmission 10 and the driveline 90, an input torque from the engine 14, clutch torques for the torque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission 10; and the motor torques for the first and second electric machines 56 and 72, respectively, as is described hereinbelow, The commanded output torque can be a tractive torque wherein torque flow originates in the engine 14 and the first and second electric machines 56 and 72 and is transferred through the transmission 10 to the driveline 90, and can be a reactive torque wherein torque flow originates in the vehicle wheels 93 of the driveline 90 and is transferred through the transmission 10 to first and second electric machines 56 and 72 and the engine 14. [0030] Final vehicle acceleration can be affected by other factors including, e.g., road load, road grade, and vehicle mass. The operating range state is determined for the transmission 10 based upon a variety of operating characteristics of the hybrid powertrain. This includes the operator torque request communicated through the accelerator pedal 113 and brake pedal 112 to the user interface 13 as previously described. The operating range state may be predicated on a hybrid powertrain torque demand caused by a command to operate the first and second electric machines 56 and 72 in an electrical energy generating mode or in a torque generating mode. The operating range state can be determined by an optimization algorithm or routine which determines optimum system efficiency based upon operator demand for power, battery state of charge, and energy efficiencies of the engine 14 and the first and second electric machines 56 and 72. The control system manages torque inputs from the engine 14 and the first and second electric machines 56 and 72 based upon an outcome of the executed optimization routine, and system efficiencies are optimized thereby, to manage fuel economy and battery charging. Furthermore, operation can be determined based upon a fault in a component or system. The HCP 5 monitors the torque- generative devices, and determines the power output from the transmission 10 required in response to the desired output torque at output member 64 to meet the operator torque request. As should be apparent from the description above, the ESD 74 and the first and second electric machines 56 and 72 are electrically-operatively coupled for power flow therebetween. Furthermore, the engine 14, the first and second electric machines 56 and 72, and the electro-mechanical transmission 10 are mechanically-operatively coupled to transfer power therebetween to generate a power flow to the output member 64. [0031] Operation of the engine 14 and transmission 10 is constrained by power, torque and speed limits of the engine 14, the first and second electric machines 56 and 72, the ESD 74 and the clutches C1 70, C2 62, C3 73, and C4 75. The operating constraints on the engine 14 and transmission 10 can be translated to a set of system constraint equations executed as one or more algorithms in one of the control modules, e.g., the HCP 5. [0032] Referring again to Fig. 1, in overall operation, the transmission 10 operates in one of the operating range states through selective actuation of one or two of the torque-transfer clutches. Torque constraints for each of the engine 14 and the first and second electric machines 56 and 72 and speed constraints for each of the engine 14, the first and second electric machines 56 and 72, and the output shaft 64 of the transmission 10 are determined. Battery power constraints for the ESD 74 are determined, and are applied to further limit the motor torque constraints for the first and second electrical machines 56 and 72. The preferred operating region for the powertrain is determined using the system constraint equation, based upon the battery power constraints, the motor torque constraints, and the speed constraints. The preferred operating region comprises a range of permissible operating torques or speeds for the engine 14 and the first and second electric machines 56 and 72. wherein, in this embodiment, [00331 By deriving and simultaneously solving dynamics equations of the transmission 10, the torque limit, in this embodiment the output torque TO, can be determined using the following linear equations: TM1 represents the output torque TO at output member 64, TM2 represents the input torque TI at input shaft 12, TM3 represents the reactive clutch torque(s) for the applied torque- transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, TA to TMI, TA toTM2, TA toTM3 are contributing factors of TA to TM1, TM2, TM3, respectively, TB to TM1, TB to TM2, TB to TM3 are contributing factors of TB to TM1, TM2, TM3, respectively, Misc_TM1, Misc_TM2, and Misc_TM3 are constants which contribute to TM1, TM2, TM3 by NI_DOT, NO_DOT, and NC_DOT (time-rate changes in the input speed, output speed and clutch slip speed) respectively, and TA and TB are the motor torques from the first and second electric machines 56 and 72. The torque parameters TM1, TM2, TM3 can be any three independent parameters, depending upon the application. [0034] The engine 14 and transmission 10 and the first and second electric machines 56 and 72 have speed constraints, torque constraints, and battery power constraints due to mechanical and system limitations. [0035] The speed constraints can include engine speed constraints of NI = 0 (engine off state), and NI ranging from 600 rpm (idle) to 6000 rpm for the engine 14. The speed constraints for the first and second electric machines 56 and 72 can be as follows: -10,500 rpm ≤NB≤+10,500 rpm. [0036] The torque constraints include engine torque constraints including TI_MIN electric machines including TA_MIN The motor torque constraints TA_MAX and TA_MIN comprise torque limits for the first electric machine 56 when working as a torque-generative motor and an electrical generator, respectively. The motor torque constraints TB_MAX and TB_MIN comprise torque limits for the second electric machine 72 when working as a torque-generative motor and an electrical generator, respectively. The maximum and minimum motor torque constraints TA_MAX, TA_MIN, TB_MAX, TB_MIN are preferably obtained from data sets stored in tabular format within one of the memory devices of one of the control modules. Such data sets are empirically derived from conventional dynamometer testing of the combined motor and power electronics (e.g., power inverter) at various temperature and voltage conditions. [0037] Battery power constraints comprise the available battery power within the range of PBAT_MIN to PBAT_MAX, wherein PBAT_MIN is maximum allowable battery charging power and PBAT_MAX is the maximum allowable battery discharging power. Battery power is defined as positive when discharging and negative when charging. [0038] Minimum and maximum values for TM1 are determined within the speed constraints, the motor torque constraints, clutch torque constraints, and the battery power constraints during ongoing operation, in order to control operation of the engine 14, the first and second electric machines 56 and 72, also referred to hereinafter as Motor A 56 and Motor B 72, and the transmission 10 to meet the operator torque request and the commanded output torque. [0039] An operating range, comprising a torque output range is determinable based upon the battery power constraints of the ESD 74. Calculation of battery power usage, PBAT is as follows: wherein PA,ELEC comprises electrical power from Motor A 56, PB,ELEC comprises electrical power from Motor B 72, and PDC_LOAD comprises known DC load, including accessory loads. [0040] Substituting equations for PA,ELEC and PB,ELEC, yields the following: wherein PA,MECH comprises mechanical power from Motor A 56, PA,LOSS comprises power losses from Motor A 56, PB,MECH comprises mechanical power from Motor B 72, and PB,LOSS comprises power losses from Motor B 72. [0041] Eq. 5 can be restated as Eq. 6, below, wherein speeds, NA and NB, and torques, TA and TB, are substituted for powers PA and PB. This includes an assumption that motor and inverter losses can be mathematically modeled as a quadratic equation based upon torque as follows: wherein NA, NB comprise speeds of Motors A and B 56 and 72, TA, TB comprise torques of Motors A and B 56 and 72, and a1, a2, a3, b1, b2, b3 each comprise quadratic coefficients which are a function of respective motor speeds, NA, NB. [0043] This reduces to Eq. 8 as follows. [0044] This reduces to Eq. 9 as follows. [0042] This can be restated as Eq. 7 as follows. [0045] This reduces to Eq. 10 as follows. [0046] This reduces to Eq. 11 as follows. [0047] The motor torques TA and TB can be transformed to Tx and Ty as follows: wherein TX is the transformation of TA, TY is the transformation of TB, and A1, A2, B1, B2 comprise application-specific scalar values. [0048] Eq. 11 can thus be further reduced as follows. [0049] Eq. 12 specifies the transformation of motor torque TA to Tx and the transformation of motor torque TB to TY. Thus, a new coordinate system referred to as TX/TY space is defined, and Eq. 13 comprises battery power, PBAT, transformed into TX/TY space. Therefore, the battery power range between maximum and minimum battery power PBAT_MAX and PBAT_MIN can be calculated and graphed as radii RMax and RMin with a center at locus (0, 0) in the transformed space TX/TY, designated by the letter K as shown with reference to Fig. 3, wherein: [0050] The minimum and maximum battery powers, PBAT_MIN and PBAT_MAX, are preferably correlated to battery physics, e.g. state of charge, temperature, voltage and usage (amp-hour/hour). The parameter C, above, is defined as the absolute minimum possible battery power at given motor speeds, NA and NB, within the motor torque limits. Physically, when TA=0 and TB=0 the output power from the first and second electric machines 56 and 72 is zero. Physically TX= 0 and TY= 0 corresponds to a maximum charging power for the ESD 74. The positive sign ('+') is defined as discharging power from the ESD 74, and the negative sign ('-') is defined as charging power into the ESD 74. RMax defines a maximum battery power, typically a discharging power, and RMin defines a maximum battery charging power. [0051] The forgoing transformations to the TX/TY space are shown in Fig. 3, with representations of the battery power constraints as concentric circles having radii of RMin and RMax ('Battery Power Constraints') and linear representations of the motor torque constraints ('Motor Torque Constraints') circumscribing an allowable operating region. Analytically, the transformed vector [TX TY] determined in Eq. 12 is solved simultaneously with the vector defined in Eq. 13 comprising the minimum and maximum battery powers identified by RMin and RMax to identify a range of allowable torques in the TX/TY space which are made up of motor torques TA and TB constrained by the minimum and maximum battery powers PBAT_MIN to PBAT_MAX. The range of allowable torques in the TX/TY space is shown with reference to Fig. 3, wherein points A, B, C, D, and E represent the bounds, and lines and radii are defined. [0052] A constant torque line can be defined in the TX/TY space, and depicted in Fig. 3 ('TM1 = C1'), comprising the limit torque TM1, described in Eq. 1, above. The limit torque TM1 comprises the output torque TO in this embodiment, Eqs. 1, 2, and 3 restated in the TX/TY space are as follows. [0053] Defining TM1_XY, TM2_XY , and TM3_XY as parts of TM1, TM2 and TM3, contributed by TA and TB only, then: [0054] The following coefficients can be defined: [0055] Thus, Eqs. 1, 2, and 3 are transformed to TX/TY space as follows. [0056] The speed constraints, motor torque constraints, and battery power constraints can be determined during ongoing operation and expressed in linear equations which are transformed to TX/TY space. Eq. 21 comprises a limit torque function describing the output torque constraint TM1, e.g., TO. [0057] The torque limit of the transmission 10, in this embodiment the output torque To, can be determined by using Eq. 21 subject to the TM2 and TM3 constraints defined by Eqs. 22 and 23to determine a transformed maximum or minimum limit torque in the TX/TY space, comprising one of TM1_XYMax and TM1_XYMin, e.g., maximum and minimum output torques TO_Max and TO_Min that have been transformed. Subsequently the transformed maximum or minimum limit torque in the TX/TY space can be retransformed out of the TX/TY space to determine maximum or minimum limit torques TM1_Max and TM1_Min for managing control and operation of the transmission 14 and the first and second electric machines 56 and 72. [0058] Fig. 4 shows motor torque constraints comprising the minimum and maximum motor torques for TA and TB transformed to TX/TY space ('Tx_ Min', 'Tx_Max', 'Ty_Min', 'Ty_Max'). Battery power constraints are transformed to the TX/TY space ('R_Min', 'R_Max') and have a center locus point K comprising (Kx, Ky) = (0,0). Constraints comprising maximum and minimum limits for an additional constraint torque are depicted ('Tm2 = Tm2_High_Lmt' and 'Tm2 = Tm2_Low_Lmt'), and comprise the range of input torques TI at input shaft 12 transformed to TX/TY space in this embodiment and can be mathematically represented by the line TM2_XY described with reference to Eq. 22, above. The lines TM2_XY described in Eq. 22 includes the TM2_Intercept having two different values corresponding to the maximum limit and the minimum limit for the engine input torque TI. Alternatively, the second input torque TM2_XY can comprise a range of clutch torques or another torque input. [0059] The operating range of the output torque To shown as the lines representing the maximum limit ('Tm1= -Tx + Ty (max)') and the minimum limit ('Tm1= -Tx + Ty (min)'). [0060] A constant torque line ('Tm1') representing line TM1_XY has a positive slope of a/b of the general form in Eq. 24: wherein a 0 and C is a constant term. In the ensuing descriptions, the line TM1_XY has a positive slope of 1:1 for purposes of illustration. The x- intercept C of Eq. 24 can change to be one of a minimum or a maximum torque. Thus, the operating range of output torque TO is shown as the lines representing the maximum limit ('Tm1= -Tx + Ty (max)') and the minimum limit ('Tml= -Tx + Ty (min)'). [0061] Fig. 5 depicts a process for determining one of the maximum and minimum output torques TO_Max and TO_Min based upon the speed constraints, motor torque constraints, and battery power constraints and constrained within the range of the additional torque input comprising Tm2. The process includes determining whether the preferred solution is a maximum value for the output, i.e., TMI_XYMax as indicated by setting a flag Tm1_Max_Flag, or alternatively whether the preferred solution is a minimum value for the output, i.e., TM1_XYMin as indicated by not setting the flag Tm1_Max_Flag. A maximum (or minimum) value for the first torque Tm1 is calculated based upon the motor torque constraints and battery power constraints in TX/TY space, comprising one of TM1_XYMax and TM1_ XYMin, and depicted as point P (or point Q) and having coordinates of (Tx, Ty) on Fig. 4 (502). A value for the second input torque TM2_XY ('Tm2_Value') is calculated using Eq. 22 (504). It is determined whether the value for the second input torque TM2_XY ('Tm2 Value') is within the operating range of the second input torque, shown as the lines representing the high limit ('Tm2_High_Lmt') and the low limit ('Tm2_Low_Lmt') (506). When it is determined that the value for the second input torque TM2_XY (Tm2_Value') is within the operating range of the second input torque, the maximum (or minimum) value for the first torque Tml depicted as point P (or point Q) and having the coordinates of (Tx, Ty) is accepted as the valid answer (518). The (Tx, Ty) point represents the preferred solution for controlling operation that can be retransformed to motor torques (TA, TB) to control operation of the first and second electric machines 56 and 72. [0062] When it is determined that the value for the second input torque TM2_XY ('Tm2_Value') is less than the operating range of the second input torque, shown as the line representing the low limit (Tm2_Low_Lmt') as shown in Fig. 4 (508), the second torque Tm2 is set to the low limit, i.e., Tm2 = Tm2_min is set equal to the line Tm2 = Tm2_Low_Lmt (510), and a search is conducted to determine a minimum (or maximum) value for the first torque Tml that is within the motor torque constraints and the battery power constraints and at the low limit (Tm2_Low_Lmt') (514). In any case, the solution comprises the minimum (or maximum) value for the first torque Tm1 that is within the motor torque constraints and the battery power constraints and the constraints of the second torque Tm2 (520). [0063] When it is determined that the value for the second input torque TM2_XY ('Tm2_Value') is greater than the operating range of the second input torque, shown as the line representing the high limit ('Tm2_High_Lmt') (508, 512), a search is conducted to determine a maximum (or minimum) value for the first torque Tm1 that is within the motor torque constraints and the battery power constraints and at the high limit ('Tm2_High_Lmt') (516). In any case, the solution comprises the minimum (or maximum) value for the first torque Tml that is within the motor torque constraints and the battery power constraints and the constraints of the second torque Tm2 (520). [0064] The preferred solution for this set of constraints (520) is the solution that has the lesser Tml point, i.e., the lesser output torque constraint TM1, when maximizing the output torque or the solution that has the greater Tm1 point, when minimizing the output torque. The solution set preferably comprises a (Tx, Ty) point representing a preferred solution for controlling operation that can be retransformed to motor torques (TA, TB) to control operation of the first and second electric machines 56 and 72. [0065] The embodiment described hereinabove is based upon the line TM1_XY having a positive slope of a/b of the general form in Eq. 24 (as above): wherein a 0 and C is a constant term, with a slope of a/b = 1:1 for purposes of illustration with the x-intercept C being changeable. The description is applicable to combinations of a > 0, b being less than 1:1 and being greater than 1:1. [0066] The disclosure has described certain preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims. CLAIMS 1. A method for controlling an electro-mechanical transmission mechanically coupled to first and second electric machines to transmit power to an output member, the method comprising: determining motor torque constraints for the first and second electric machines; determining battery power constraints for an electrical energy storage device electrically connected to the first and second electric machines; determining a range for an additional torque input to the electro- mechanical transmission; and determining a preferred output torque to the output member of the electro-mechanical transmission that is achievable within the motor torque constraints, is achievable within the range of the additional torque input, and is based upon the battery power constraints. 2. The method of claim 1, wherein the preferred output torque comprises a commanded output torque to the output member in response an operator torque request. 3. The method of claim 2, wherein the preferred output torque comprises a maximum tractive torque to the output member. 4. The method of claim 2, wherein the preferred output torque comprises a maximum regenerative torque to the output member. 5. The method of claim 1, wherein the additional torque input comprises an engine input torque. 6. The method of claim 1, wherein the additional torque input comprises a clutch reactive torque. 7. The method of claim 1, further comprising controlling operation of the electro-mechanical transmission and the first and second electric machines to achieve the preferred output torque at the output member based upon the motor torque constraints, the range of the additional torque input and the battery power constraints. 8. The method of claim 7, further comprising determining a preferred output torque to the output member of the electro-mechanical transmission that is achievable within the range of the additional torque input and that minimizes a violation of a maximum battery power constraint when the additional torque input is achievable within the motor torque constraints and the additional torque input exceeds the maximum battery power constraint. 9. The method of claim 7, further comprising determining a preferred output torque to the output member of the electro-mechanical transmission that is achievable within the range of the additional torque input and is constrained by a maximum battery power constraint when the additional torque input is achievable within the motor torque constraints and the additional torque input is achievable within the maximum battery power constraint. 10. The method of claim 7, further comprising limiting the preferred output torque to the output member of the electro-mechanical transmission to an output torque achievable within the motor torque constraints and achievable within the battery power constraints. 11. The method of claim 10, wherein the maximum battery power constraint comprises a maximum battery discharging power. 12. The method of claim 10, wherein the minimum battery power constraint comprises a minimum battery charging power. 13. The method of claim 1, wherein the additional torque input comprises an input torque to an input shaft from an internal combustion engine mechanically coupled to the electro-mechanical transmission. 14. The method of claim 1, wherein the additional torque input comprises torque transfer across an applied torque transfer clutch in the transmission. 15. The method of claim 1, further comprising: formulating mathematical equations representing maximum and minimum motor torque constraints for the first and second electric machines and representing maximum and minimum battery power constraints; formulating a mathematical equation representing the output torque; formulating mathematical equations representing the range for the additional torque input; transforming the mathematical equations representing the maximum and minimum battery power constraints to equations of concentric circles having respective radii; transforming the mathematical equations representing the maximum and minimum motor torque constraints for the first and second electric machines to equations comprising lines; transforming the mathematical equations representing the range for the additional torque input to equations comprising lines; and transforming the mathematical equation representing the output torque to an equation comprising a line. 16. The method of claim 15, further comprising: determining at least one transformed achievable output torque based upon the transformed motor torque constraints for the first and second electric machines, the transformed battery power constraints, and the transformed range for the additional torque input; determining a transformed achievable maximum output torque from the electro-mechanical transmission; and, retransforming the transformed achievable maximum output torque to determine preferred motor torques for the first and second electric machines. 34 7. The method of claim 15, comprising calculating at least one intersection of the transformed mathematical equations representing the maximum and minimum battery power constraints, the transformed mathematical equations representing the maximum and minimum motor torque constraints for the first and second electric machines, the transformed mathematical equations representing the range for the additional torque input, and the transformed mathematical equation representing the output torque. A method for controlling an electro-mechanical transmission mechanically coupled to first and second electric machines to transmit power to an output member includes determining motor torque constraints and battery power constraints. A preferred output torque to an output member is determined that is achievable within the motor torque constraints, within a range for an additional torque input and based upon the battery power constraints.

Full Text

SYSTEM CONSTRAINTS METHOD OF CONTROLLING OPERATION
OF AN ELECTRO-MECHANICAL TRANSMISSION WITH AN
ADDITIONAL CONSTRAINT RANGE
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application
No. 60/984,492 filed on 11/01/2007 which is hereby incorporated herein by
reference.
TECHNICAL FIELD
[0002] This disclosure pertains to control systems for electro-mechanical
transmissions.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0004] Known hybrid powertrain architectures can include multiple
torque-generative devices, including internal combustion engines and non-
combustion machines, e.g., electric machines, which transmit torque through a
transmission device to an output member. One exemplary hybrid powertrain
includes a two-mode, compound-split, electro-mechanical transmission which
utilizes an input member for receiving tractive torque from a prime mover
power source, preferably an internal combustion engine, and an output
member. The output member can be operatively connected to a driveline for a
motor vehicle for transmitting tractive torque thereto. Machines, operative as

motors or generators, can generate torque inputs to the transmission
independently of a torque input from the internal combustion engine. The
machines may transform vehicle kinetic energy transmitted through the
vehicle driveline to energy that is storable in an energy storage device. A
control system monitors various inputs from the vehicle and the operator and
provides operational control of the hybrid powertrain, including controlling
transmission operating state and gear shifting, controlling the torque-
generative devices, and regulating the power interchange among the energy
storage device and the machines to manage outputs of the transmission,
including torque and rotational speed.
SUMMARY
[0005] A powertrain includes an electro-mechanical transmission
mechanically-operatively coupled to an internal combustion engine and first
and second electric machines to transmit power to an output member. A
method for controlling the electro-mechanical transmission includes
determining motor torque constraints for the first and second electric
machines, and determining battery power constraints for an electrical energy
storage device. A range for an additional torque input to the electro-
mechanical transmission is determined. A preferred output torque to the
output member of the electro-mechanical transmission is determined that is
achievable within the motor torque constraints and within the range of the
additional torque input and is based upon the battery power constraints.
BRIEF DESCRIPTION OF THE DRAWINGS

[0006] One or more embodiments will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in
accordance with the present disclosure;
[0008] Fig. 2 is a schematic diagram of an exemplary architecture for a
control system and powertrain, in accordance with the present disclosure;
[0009] Figs. 3-4 are graphical diagrams, in accordance with the present
disclosure; and
[0010] Fig. 5 is an algorithmic flowchart, in accordance with the present
disclosure.
DETAILED DESCRIPTION
[0011] Referring now to the drawings, wherein the showings are for the
purpose of illustrating certain exemplary embodiments only and not for the
purpose of limiting the same, Figs. 1 and 2 depict an exemplary electro-
mechanical hybrid powertrain. The exemplary electro-mechanical hybrid
powertrain in accordance with the present disclosure is depicted in Fig. 1,
comprising a two-mode, compound-split, electro-mechanical hybrid
transmission 10 operatively connected to an engine 14 and first and second
electric machines ('MG-A') 56 and ('MG-B') 72. The engine 14 and first and
second electric machines 56 and 72 each generate power which can be
transferred to the transmission 10. The power generated by the engine 14 and
the first and second electric machines 56 and 72 and transferred to the
transmission 10 is described in terms of input and motor torques, referred to

herein as TI, TA, and TB respectively, and speed, referred to herein as NI, NA,
and NB, respectively.
[0012] The exemplary engine 14 comprises a multi-cylinder internal
combustion engine selectively operative in several states to transfer torque to
the transmission 10 via an input shaft 12, and can be either a spark-ignition or
a compression-ignition engine. The engine 14 includes a crankshaft (not
shown) operatively coupled to the input shaft 12 of the transmission 10. A
rotational speed sensor 11 monitors rotational speed of the input shaft 12.
Power output from the engine 14, comprising rotational speed and engine
torque, can differ from the input speed NI and the input torque TI to the
transmission 10 due to placement of torque-consuming components on the
input shaft 12 between the engine 14 and the transmission 10, e.g., a hydraulic
pump (not shown) and/or a torque management device (not shown).
[0013] The exemplary transmission 10 comprises three planetary-gear sets
24, 26 and 28, and four selectively engageable torque-transferring devices, i.e.,
clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutches refer to
any type of friction torque transfer device including single or compound plate
clutches or packs, band clutches, and brakes, for example. A hydraulic control
circuit 42, preferably controlled by a transmission control module (hereafter
'TCM') 17, is operative to control clutch states. Clutches C2 62 and C4 75
preferably comprise hydraulically-applied rotating friction clutches. Clutches
C1 70 and C3 73 preferably comprise hydraulically-controlled stationary
devices that can be selectively grounded to a transmission case 68. Each of
the clutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulically

applied, selectively receiving pressurized hydraulic fluid via the hydraulic
control circuit 42.
[0014] The first and second electric machines 56 and 72 preferably
comprise three-phase AC machines, each including a stator (not shown) and a
rotor (not shown), and respective resolvers 80 and 82. The motor stator for
each machine is grounded to an outer portion of the transmission case 68, and
includes a stator core with coiled electrical windings extending therefrom.
The rotor for the first electric machine 56 is supported on a hub plate gear that
is operatively attached to shaft 60 via the second planetary gear set 26. The
rotor for the second electric machine 72 is fixedly attached to a sleeve shaft
hub 66.
[0015] Each of the resolvers 80 and 82 preferably comprises a variable
reluctance device including a resolver stator (not shown) and a resolver rotor
(not shown). The resolvers 80 and 82 are appropriately positioned and
assembled on respective ones of the first and second electric machines 56 and
72. Stators of respective ones of the resolvers 80 and 82 are operatively
connected to one of the stators for the first and second electric machines 56
and 72. The resolver rotors are operatively connected to the rotor for the
corresponding first and second electric machines 56 and 72. Each of the
resolvers 80 and 82 is signally and operatively connected to a transmission
power inverter control module (hereafter 'TPIM') 19, and each senses and
monitors rotational position of the resolver rotor relative to the resolver stator,
thus monitoring rotational position of respective ones of first and second
electric machines 56 and 72. Additionally, the signals output from the

resolvers 80 and 82 are interpreted to provide the rotational speeds for first
and second electric machines 56 and 72, i.e., NAand NB, respectively.
[0016] The transmission 10 includes an output member 64, e.g. a shaft,
which is operably connected to a driveline 90 for a vehicle (not shown), to
provide output power to the driveline 90 that is transferred to vehicle wheels
93, one of which is shown in Fig. 1. The output power at the output member
64 is characterized in terms of an output rotational speed NO and an output
torque TO. A transmission output speed sensor 84 monitors rotational speed
and rotational direction of the output member 64. Each of the vehicle wheels
93 is preferably equipped with a sensor 94 adapted to monitor wheel speed,
the output of which is monitored by a control module of a distributed control
module system described with respect to Fig. 2, to determine vehicle speed,
and absolute and relative wheel speeds for braking control, traction control,
and vehicle acceleration management.
[0017] The input torque from the engine 14 and the motor torques from
the first and second electric machines 56 and 72 (TI, TA, and TB respectively)
are generated as a result of energy conversion from fuel or electrical potential
stored in an electrical energy storage device (hereafter 'ESD') 74. The ESD
74 is high voltage DC-coupled to the TPIM 19 via DC transfer conductors 27.
The transfer conductors 27 include a contactor switch 38. When the contactor
switch 38 is closed, under normal operation, electric current can flow between
the ESD 74 and the TPIM 19. When the contactor switch 38 is opened electric
current flow between the ESD 74 and the TPIM 19 is interrupted. The TPIM
19 transmits electrical power to and from the first electric machine 56 by
transfer conductors 29, and the TPIM 19 similarly transmits electrical power

to and from the second electric machine 72 by transfer conductors 31 to meet
the torque commands for the first and second electric machines 56 and 72 in
response to the motor torques TA and TB. Electrical current is transmitted to
and from the ESD 74 in accordance with whether the ESD 74 is being charged
or discharged.
[0018] The TPIM 19 includes the pair of power inverters (not shown) and
respective motor control modules (not shown) configured to receive the torque
commands and control inverter states therefrom for providing motor drive or
regeneration functionality to meet the commanded motor torques TA and TB.
The power inverters comprise known complementary three-phase power
electronics devices, and each includes a plurality of insulated gate bipolar
transistors (not shown) for converting DC power from the ESD 74 to AC
power for powering respective ones of the first and second electric machines
56 and 72, by switching at high frequencies. The insulated gate bipolar
transistors form a switch mode power supply configured to receive control
commands. There is typically one pair of insulated gate bipolar transistors for
each phase of each of the three-phase electric machines. States of the
insulated gate bipolar transistors are controlled to provide motor drive
mechanical power generation or electric power regeneration functionality.
The three-phase inverters receive or supply DC electric power via DC transfer
conductors 27 and transform it to or from three-phase AC power, which is
conducted to or from the first and second electric machines 56 and 72 for
operation as motors or generators via transfer conductors 29 and 31
respectively.

[0019] Fig. 2 is a schematic block diagram of the distributed control
module system. The elements described hereinafter comprise a subset of an
overall vehicle control architecture, and provide coordinated system control of
the exemplary hybrid powertrain described in Fig. 1. The distributed control
module system synthesizes pertinent information and inputs, and executes
algorithms to control various actuators to meet control objectives, including
objectives related to fuel economy, emissions, performance, drivability, and
protection of hardware, including batteries of ESD 74 and the first and second
electric machines 56 and 72. The distributed control module system includes
an engine control module (hereafter 'ECM') 23, the TCM 17, a battery pack
control module (hereafter 'BPCM') 21, and the TPIM 19. A hybrid control
module (hereafter 'HCP') 5 provides supervisory control and coordination of
the ECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface
('UI') 13 is signally connected to a plurality of devices through which a
vehicle operator controls or directs operation of the electro-mechanical hybrid
powertrain. The devices include an accelerator pedal 113 ('AP'), an operator
brake pedal 112 ('BP'), a transmission gear selector 114 ('PRNDL'), and a
vehicle speed cruise control (not shown). The transmission gear selector 114
may have a discrete number of operator-selectable positions, including the
rotational direction of the output member 64 to enable one of a forward and a
reverse direction.
[0020] The aforementioned control modules communicate with other
control modules, sensors, and actuators via a local area network (hereafter
'LAN') bus 6. The LAN bus 6 allows for structured communication of states
of operating parameters and actuator command signals between the various

control modules. The specific communication protocol utilized is application-
specific. The LAN bus 6 and appropriate protocols provide for robust
messaging and multi-control module interfacing between the aforementioned
control modules, and other control modules providing functionality including
e.g., antilock braking, traction control, and vehicle stability. Multiple
communications buses may be used to improve communications speed and
provide some level of signal redundancy and integrity. Communication
between individual control modules can also be effected using a direct link,
e.g., a serial peripheral interface ('SPI') bus (not shown).
[0021] The HCP 5 provides supervisory control of the hybrid powertrain,
serving to coordinate operation of the ECM 23, TCM 17, TPIM 19, and
BPCM 21. Based upon various input signals from the user interface 13 and
the hybrid powertrain, including the ESD 74, the HCP 5 determines an
operator torque request, an output torque command, an engine input torque
command, clutch torque(s) for the applied torque-transfer clutches C1 70, C2
62, C3 73, C4 75 of the transmission 10, and the motor torques TA and TB for
the first and second electric machines 56 and 72. The TCM 17 is operatively
connected to the hydraulic control circuit 42 and provides various functions
including monitoring various pressure sensing devices (not shown) and
generating and communicating control signals to various solenoids (not
shown) thereby controlling pressure switches and control valves contained
within the hydraulic control circuit 42.
[0022] The ECM 23 is operatively connected to the engine 14, and
functions to acquire data from sensors and control actuators of the engine 14
over a plurality of discrete lines, shown for simplicity as an aggregate bi-

directional interface cable 35. The ECM 23 receives the engine input torque
command from the HCP 5. The ECM 23 determines the actual engine input
torque, T|, provided to the transmission 10 at that point in time based upon
monitored engine speed and load, which is communicated to the HCP 5. The
ECM 23 monitors input from the rotational speed sensor 11 to determine the
engine input speed to the input shaft 12, which translates to the transmission
input speed, N\. The ECM 23 monitors inputs from sensors (not shown) to
determine states of other engine operating parameters including, e.g., a
manifold pressure, engine coolant temperature, ambient air temperature, and
ambient pressure. The engine load can be determined, for example, from the
manifold pressure, or alternatively, from monitoring operator input to the
accelerator pedal 113. The ECM 23 generates and communicates command
signals to control engine actuators, including, e.g., fuel injectors, ignition
modules, and throttle control modules, none of which are shown.
[0023] The TCM 17 is operatively connected to the transmission 10 and
monitors inputs from sensors (not shown) to determine states of transmission
operating parameters. The TCM 17 generates and communicates command
signals to control the transmission 10, including controlling the hydraulic
circuit 42. Inputs from the TCM 17 to the HCP 5 include estimated clutch
torques for each of the clutches, i.e., C1 70, C2 62, C3 73, and C4 75, and
rotational output speed, NO, of the output member 64. Other actuators and
sensors may be used to provide additional information from the TCM 17 to the
HCP 5 for control purposes. The TCM 17 monitors inputs from pressure
switches (not shown) and selectively actuates pressure control solenoids (not
shown) and shift solenoids (not shown) of the hydraulic circuit 42 to

selectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75 to
achieve various transmission operating range states, as described hereinbelow.
[0024] The BPCM 21 is signally connected to sensors (not shown) to
monitor the ESD 74, including states of electrical current and voltage
parameters, to provide information indicative of parametric states of the
batteries of the ESD 74 to the HCP 5. The parametric states of the batteries
preferably include battery state-of-charge, battery voltage, battery temperature,
and available battery power, referred to as a range PBAT_MIN to PBAT_MAX.
[0025] A brake control module (hereafter 'BrCM') 22 is operatively
connected to friction brakes (not shown) on each of the vehicle wheels 93.
The BrCM 22 monitors the operator input to the brake pedal 112 and
generates control signals to control the friction brakes and sends a control
signal to the HCP 5 to operate the first and second electric machines 56 and 72
based thereon.
[0026] Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM
21, and BrCM 22 is preferably a general-purpose digital computer comprising
a microprocessor or central processing unit, storage mediums comprising read
only memory ('ROM'), random access memory ('RAM'), electrically
programmable read only memory ('EPROM'), a 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 of the control modules has a set of control algorithms,
comprising resident program instructions and calibrations stored in one of the
storage mediums and executed to provide the respective functions of each
computer. Information transfer between the control modules is preferably

accomplished using the LAN bus 6 and serial peripheral interface buses. The
control algorithms are 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 to monitor inputs from the sensing devices and execute control and
diagnostic routines to control operation of the actuators, using preset
calibrations. Loop cycles are executed at regular intervals, for example each
3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing operation of the
hybrid powertrain. Alternatively, algorithms may be executed in response to
the occurrence of an event.
[0027] The exemplary hybrid powertrain selectively operates in one of
several operating range states that can be described in terms of an engine state
comprising one of an engine-on state ('ON') and an engine-off state ('OFF'),
and a transmission state comprising a plurality of fixed gears and continuously
variable operating modes, described with reference to Table 1, below.
Table 1

[0028] Each of the transmission operating range states is described in the
table and indicates which of the specific clutches C1 70, C2 62, C3 73, and C4
75 are applied for each of the operating range states. A first continuously
variable mode, i.e., EVT Mode 1, or Ml, is selected by applying clutch C1 70
only in order to "ground" the outer gear member of the third planetary gear set
28. The engine state can be one of ON ('M1_Eng_On') or OFF
('M1_Eng_Off). A second continuously variable mode, i.e., EVT Mode 2, or
M2, is selected by applying clutch C2 62 only to connect the shaft 60 to the
carrier of the third planetary gear set 28. The engine state can be one of ON
('M2_Eng_On') or OFF ('M2_Eng_Off). For purposes of this description,
when the engine state is OFF, the engine input speed is equal to zero
revolutions per minute ('RPM'), i.e., the engine crankshaft is not rotating. A
fixed gear operation provides a fixed ratio operation of input-to-output speed
of the transmission 10, i.e., NI/NO. A first fixed gear operation ('G1') is
selected by applying clutches C1 70 and C4 75. A second fixed gear operation
('G2') is selected by applying clutches C1 70 and C2 62. A third fixed gear
operation ('G3') is selected by applying clutches C2 62 and C4 75. A fourth
fixed gear operation ('G4') is selected by applying clutches C2 62 and C3 73.
The fixed ratio operation of input-to-output speed increases with increased
fixed gear operation due to decreased gear ratios in the planetary gears 24, 26,
and 28. The rotational speeds of the first and second electric machines 56 and
72, NAand NB respectively, are dependent on internal rotation of the
mechanism as defined by the clutching and are proportional to the input speed
measured at the input shaft 12.

[0029] In response to operator input via the accelerator pedal 113 and
brake pedal 112 as captured by the user interface 13, the HCP 5 and one or
more of the other control modules determine torque commands to control the
torque generative devices comprising the engine 14 and first and second
electric machines 56 and 72 to meet the operator torque request at the output
member 64 and transferred to the driveline 90. Based upon input signals from
the user interface 13 and the hybrid powertrain including the ESD 74, the HCP
5 determines the operator torque request, a commanded output torque between
the transmission 10 and the driveline 90, an input torque from the engine 14,
clutch torques for the torque-transfer clutches C1 70, C2 62, C3 73, C4 75 of
the transmission 10; and the motor torques for the first and second electric
machines 56 and 72, respectively, as is described hereinbelow, The
commanded output torque can be a tractive torque wherein torque flow
originates in the engine 14 and the first and second electric machines 56 and
72 and is transferred through the transmission 10 to the driveline 90, and can
be a reactive torque wherein torque flow originates in the vehicle wheels 93 of
the driveline 90 and is transferred through the transmission 10 to first and
second electric machines 56 and 72 and the engine 14.
[0030] Final vehicle acceleration can be affected by other factors
including, e.g., road load, road grade, and vehicle mass. The operating range
state is determined for the transmission 10 based upon a variety of operating
characteristics of the hybrid powertrain. This includes the operator torque
request communicated through the accelerator pedal 113 and brake pedal 112
to the user interface 13 as previously described. The operating range state
may be predicated on a hybrid powertrain torque demand caused by a

command to operate the first and second electric machines 56 and 72 in an
electrical energy generating mode or in a torque generating mode. The
operating range state can be determined by an optimization algorithm or
routine which determines optimum system efficiency based upon operator
demand for power, battery state of charge, and energy efficiencies of the
engine 14 and the first and second electric machines 56 and 72. The control
system manages torque inputs from the engine 14 and the first and second
electric machines 56 and 72 based upon an outcome of the executed
optimization routine, and system efficiencies are optimized thereby, to manage
fuel economy and battery charging. Furthermore, operation can be determined
based upon a fault in a component or system. The HCP 5 monitors the torque-
generative devices, and determines the power output from the transmission 10
required in response to the desired output torque at output member 64 to meet
the operator torque request. As should be apparent from the description
above, the ESD 74 and the first and second electric machines 56 and 72 are
electrically-operatively coupled for power flow therebetween. Furthermore,
the engine 14, the first and second electric machines 56 and 72, and the
electro-mechanical transmission 10 are mechanically-operatively coupled to
transfer power therebetween to generate a power flow to the output member
64.
[0031] Operation of the engine 14 and transmission 10 is constrained by
power, torque and speed limits of the engine 14, the first and second electric
machines 56 and 72, the ESD 74 and the clutches C1 70, C2 62, C3 73, and
C4 75. The operating constraints on the engine 14 and transmission 10 can be

translated to a set of system constraint equations executed as one or more
algorithms in one of the control modules, e.g., the HCP 5.
[0032] Referring again to Fig. 1, in overall operation, the transmission 10
operates in one of the operating range states through selective actuation of one
or two of the torque-transfer clutches. Torque constraints for each of the
engine 14 and the first and second electric machines 56 and 72 and speed
constraints for each of the engine 14, the first and second electric machines 56
and 72, and the output shaft 64 of the transmission 10 are determined. Battery
power constraints for the ESD 74 are determined, and are applied to further
limit the motor torque constraints for the first and second electrical machines
56 and 72. The preferred operating region for the powertrain is determined
using the system constraint equation, based upon the battery power
constraints, the motor torque constraints, and the speed constraints. The
preferred operating region comprises a range of permissible operating torques
or speeds for the engine 14 and the first and second electric machines 56 and
72.
wherein, in this embodiment,
[00331 By deriving and simultaneously solving dynamics equations of the
transmission 10, the torque limit, in this embodiment the output torque TO, can
be determined using the following linear equations:

TM1 represents the output torque TO at output member 64,
TM2 represents the input torque TI at input shaft 12,
TM3 represents the reactive clutch torque(s) for the applied torque-
transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission
10,
TA to TMI, TA toTM2, TA toTM3 are contributing factors of TA to TM1,
TM2, TM3, respectively,
TB to TM1, TB to TM2, TB to TM3 are contributing factors of TB to TM1,
TM2, TM3, respectively,
Misc_TM1, Misc_TM2, and Misc_TM3 are constants which contribute
to TM1, TM2, TM3 by NI_DOT, NO_DOT, and NC_DOT (time-rate
changes in the input speed, output speed and clutch slip speed)
respectively, and
TA and TB are the motor torques from the first and second electric
machines 56 and 72.
The torque parameters TM1, TM2, TM3 can be any three independent
parameters, depending upon the application.
[0034] The engine 14 and transmission 10 and the first and second electric
machines 56 and 72 have speed constraints, torque constraints, and battery
power constraints due to mechanical and system limitations.
[0035] The speed constraints can include engine speed constraints of NI =
0 (engine off state), and NI ranging from 600 rpm (idle) to 6000 rpm for the
engine 14. The speed constraints for the first and second electric machines 56
and 72 can be as follows:

-10,500 rpm ≤NB≤+10,500 rpm.
[0036] The torque constraints include engine torque constraints including
TI_MIN electric machines including TA_MIN The motor torque constraints TA_MAX and TA_MIN comprise torque limits for
the first electric machine 56 when working as a torque-generative motor and
an electrical generator, respectively. The motor torque constraints TB_MAX and
TB_MIN comprise torque limits for the second electric machine 72 when
working as a torque-generative motor and an electrical generator, respectively.
The maximum and minimum motor torque constraints TA_MAX, TA_MIN,
TB_MAX, TB_MIN are preferably obtained from data sets stored in tabular format
within one of the memory devices of one of the control modules. Such data
sets are empirically derived from conventional dynamometer testing of the
combined motor and power electronics (e.g., power inverter) at various
temperature and voltage conditions.
[0037] Battery power constraints comprise the available battery power
within the range of PBAT_MIN to PBAT_MAX, wherein PBAT_MIN is maximum
allowable battery charging power and PBAT_MAX is the maximum allowable
battery discharging power. Battery power is defined as positive when
discharging and negative when charging.
[0038] Minimum and maximum values for TM1 are determined within the
speed constraints, the motor torque constraints, clutch torque constraints, and
the battery power constraints during ongoing operation, in order to control
operation of the engine 14, the first and second electric machines 56 and 72,
also referred to hereinafter as Motor A 56 and Motor B 72, and the

transmission 10 to meet the operator torque request and the commanded
output torque.
[0039] An operating range, comprising a torque output range is
determinable based upon the battery power constraints of the ESD 74.
Calculation of battery power usage, PBAT is as follows:

wherein PA,ELEC comprises electrical power from Motor A 56,
PB,ELEC comprises electrical power from Motor B 72, and
PDC_LOAD comprises known DC load, including accessory loads.
[0040] Substituting equations for PA,ELEC and PB,ELEC, yields the following:

wherein PA,MECH comprises mechanical power from Motor A 56,
PA,LOSS comprises power losses from Motor A 56,
PB,MECH comprises mechanical power from Motor B 72, and
PB,LOSS comprises power losses from Motor B 72.
[0041] Eq. 5 can be restated as Eq. 6, below, wherein speeds, NA and NB,
and torques, TA and TB, are substituted for powers PA and PB. This includes an
assumption that motor and inverter losses can be mathematically modeled as a
quadratic equation based upon torque as follows:

wherein NA, NB comprise speeds of Motors A and B 56 and 72,
TA, TB comprise torques of Motors A and B 56 and 72, and
a1, a2, a3, b1, b2, b3 each comprise quadratic coefficients which are
a function of respective motor speeds, NA, NB.
[0043] This reduces to Eq. 8 as follows.
[0044] This reduces to Eq. 9 as follows.
[0042] This can be restated as Eq. 7 as follows.

[0045] This reduces to Eq. 10 as follows.

[0046] This reduces to Eq. 11 as follows.

[0047] The motor torques TA and TB can be transformed to Tx and Ty as
follows:

wherein TX is the transformation of TA,
TY is the transformation of TB, and

A1, A2, B1, B2 comprise application-specific scalar values.
[0048] Eq. 11 can thus be further reduced as follows.

[0049] Eq. 12 specifies the transformation of motor torque TA to Tx and
the transformation of motor torque TB to TY. Thus, a new coordinate system
referred to as TX/TY space is defined, and Eq. 13 comprises battery power,
PBAT, transformed into TX/TY space. Therefore, the battery power range
between maximum and minimum battery power PBAT_MAX and PBAT_MIN can be
calculated and graphed as radii RMax and RMin with a center at locus (0, 0) in
the transformed space TX/TY, designated by the letter K as shown with
reference to Fig. 3, wherein:

[0050] The minimum and maximum battery powers, PBAT_MIN and
PBAT_MAX, are preferably correlated to battery physics, e.g. state of charge,
temperature, voltage and usage (amp-hour/hour). The parameter C, above, is
defined as the absolute minimum possible battery power at given motor
speeds, NA and NB, within the motor torque limits. Physically, when TA=0 and
TB=0 the output power from the first and second electric machines 56 and 72

is zero. Physically TX= 0 and TY= 0 corresponds to a maximum charging
power for the ESD 74. The positive sign ('+') is defined as discharging power
from the ESD 74, and the negative sign ('-') is defined as charging power into
the ESD 74. RMax defines a maximum battery power, typically a discharging
power, and RMin defines a maximum battery charging power.
[0051] The forgoing transformations to the TX/TY space are shown in Fig.
3, with representations of the battery power constraints as concentric circles
having radii of RMin and RMax ('Battery Power Constraints') and linear
representations of the motor torque constraints ('Motor Torque Constraints')
circumscribing an allowable operating region. Analytically, the transformed
vector [TX TY] determined in Eq. 12 is solved simultaneously with the vector
defined in Eq. 13 comprising the minimum and maximum battery powers
identified by RMin and RMax to identify a range of allowable torques in the
TX/TY space which are made up of motor torques TA and TB constrained by the
minimum and maximum battery powers PBAT_MIN to PBAT_MAX. The range of
allowable torques in the TX/TY space is shown with reference to Fig. 3,
wherein points A, B, C, D, and E represent the bounds, and lines and radii are
defined.
[0052] A constant torque line can be defined in the TX/TY space, and
depicted in Fig. 3 ('TM1 = C1'), comprising the limit torque TM1, described in
Eq. 1, above. The limit torque TM1 comprises the output torque TO in this
embodiment, Eqs. 1, 2, and 3 restated in the TX/TY space are as follows.

[0053] Defining TM1_XY, TM2_XY , and TM3_XY as parts of TM1, TM2 and TM3,
contributed by TA and TB only, then:

[0054] The following coefficients can be defined:

[0055] Thus, Eqs. 1, 2, and 3 are transformed to TX/TY space as follows.

[0056] The speed constraints, motor torque constraints, and battery power
constraints can be determined during ongoing operation and expressed in
linear equations which are transformed to TX/TY space. Eq. 21 comprises a
limit torque function describing the output torque constraint TM1, e.g., TO.
[0057] The torque limit of the transmission 10, in this embodiment the
output torque To, can be determined by using Eq. 21 subject to the TM2
and TM3 constraints defined by Eqs. 22 and 23to determine a transformed
maximum or minimum limit torque in the TX/TY space, comprising one
of TM1_XYMax and TM1_XYMin, e.g., maximum and minimum output
torques TO_Max and TO_Min that have been transformed. Subsequently the
transformed maximum or minimum limit torque in the TX/TY space can
be retransformed out of the TX/TY space to determine maximum or
minimum limit torques TM1_Max and TM1_Min for managing control and
operation of the transmission 14 and the first and second electric
machines 56 and 72.
[0058] Fig. 4 shows motor torque constraints comprising the minimum and
maximum motor torques for TA and TB transformed to TX/TY space
('Tx_ Min', 'Tx_Max', 'Ty_Min', 'Ty_Max'). Battery power constraints are
transformed to the TX/TY space ('R_Min', 'R_Max') and have a center locus
point K comprising (Kx, Ky) = (0,0). Constraints comprising maximum and
minimum limits for an additional constraint torque are depicted ('Tm2 =
Tm2_High_Lmt' and 'Tm2 = Tm2_Low_Lmt'), and comprise the range of
input torques TI at input shaft 12 transformed to TX/TY space in this
embodiment and can be mathematically represented by the line TM2_XY

described with reference to Eq. 22, above. The lines TM2_XY described in Eq.
22 includes the TM2_Intercept having two different values corresponding to the
maximum limit and the minimum limit for the engine input torque TI.
Alternatively, the second input torque TM2_XY can comprise a range of clutch
torques or another torque input.
[0059] The operating range of the output torque To shown as the lines
representing the maximum limit ('Tm1= -Tx + Ty (max)') and the minimum
limit ('Tm1= -Tx + Ty (min)').
[0060] A constant torque line ('Tm1') representing line TM1_XY has a positive
slope of a/b of the general form in Eq. 24:

wherein a 0 and C is a constant term. In the ensuing descriptions,
the line TM1_XY has a positive slope of 1:1 for purposes of illustration. The x-
intercept C of Eq. 24 can change to be one of a minimum or a maximum
torque. Thus, the operating range of output torque TO is shown as the lines
representing the maximum limit ('Tm1= -Tx + Ty (max)') and the minimum
limit ('Tml= -Tx + Ty (min)').
[0061] Fig. 5 depicts a process for determining one of the maximum and
minimum output torques TO_Max and TO_Min based upon the speed constraints,
motor torque constraints, and battery power constraints and constrained within
the range of the additional torque input comprising Tm2. The process
includes determining whether the preferred solution is a maximum value for
the output, i.e., TMI_XYMax as indicated by setting a flag Tm1_Max_Flag, or

alternatively whether the preferred solution is a minimum value for the output,
i.e., TM1_XYMin as indicated by not setting the flag Tm1_Max_Flag. A
maximum (or minimum) value for the first torque Tm1 is calculated based
upon the motor torque constraints and battery power constraints in TX/TY
space, comprising one of TM1_XYMax and TM1_ XYMin, and depicted as point
P (or point Q) and having coordinates of (Tx, Ty) on Fig. 4 (502). A value for
the second input torque TM2_XY ('Tm2_Value') is calculated using Eq. 22
(504). It is determined whether the value for the second input torque TM2_XY
('Tm2 Value') is within the operating range of the second input torque, shown
as the lines representing the high limit ('Tm2_High_Lmt') and the low limit
('Tm2_Low_Lmt') (506). When it is determined that the value for the second
input torque TM2_XY (Tm2_Value') is within the operating range of the second
input torque, the maximum (or minimum) value for the first torque Tml
depicted as point P (or point Q) and having the coordinates of (Tx, Ty) is
accepted as the valid answer (518). The (Tx, Ty) point represents the
preferred solution for controlling operation that can be retransformed to motor
torques (TA, TB) to control operation of the first and second electric machines
56 and 72.
[0062] When it is determined that the value for the second input torque
TM2_XY ('Tm2_Value') is less than the operating range of the second input
torque, shown as the line representing the low limit (Tm2_Low_Lmt') as
shown in Fig. 4 (508), the second torque Tm2 is set to the low limit, i.e., Tm2
= Tm2_min is set equal to the line Tm2 = Tm2_Low_Lmt (510), and a search
is conducted to determine a minimum (or maximum) value for the first torque
Tml that is within the motor torque constraints and the battery power

constraints and at the low limit (Tm2_Low_Lmt') (514). In any case, the
solution comprises the minimum (or maximum) value for the first torque Tm1
that is within the motor torque constraints and the battery power constraints
and the constraints of the second torque Tm2 (520).
[0063] When it is determined that the value for the second input torque
TM2_XY ('Tm2_Value') is greater than the operating range of the second input
torque, shown as the line representing the high limit ('Tm2_High_Lmt') (508,
512), a search is conducted to determine a maximum (or minimum) value for
the first torque Tm1 that is within the motor torque constraints and the battery
power constraints and at the high limit ('Tm2_High_Lmt') (516). In any case,
the solution comprises the minimum (or maximum) value for the first torque
Tml that is within the motor torque constraints and the battery power
constraints and the constraints of the second torque Tm2 (520).
[0064] The preferred solution for this set of constraints (520) is the solution
that has the lesser Tml point, i.e., the lesser output torque constraint TM1,
when maximizing the output torque or the solution that has the greater Tm1
point, when minimizing the output torque. The solution set preferably
comprises a (Tx, Ty) point representing a preferred solution for controlling
operation that can be retransformed to motor torques (TA, TB) to control
operation of the first and second electric machines 56 and 72.
[0065] The embodiment described hereinabove is based upon the line
TM1_XY having a positive slope of a/b of the general form in Eq. 24 (as above):

wherein a 0 and C is a constant term, with a slope of a/b = 1:1 for
purposes of illustration with the x-intercept C being changeable. The
description is applicable to combinations of a > 0, b being less than 1:1 and being greater than 1:1.
[0066] The disclosure has described certain preferred embodiments and
modifications thereto. Further modifications and alterations may occur to
others upon reading and understanding the specification. Therefore, it is
intended that the disclosure not be limited to the particular embodiment(s)
disclosed as the best mode contemplated for carrying out this disclosure, but
that the disclosure will include all embodiments falling within the scope of the
appended claims.

CLAIMS
1. A method for controlling an electro-mechanical transmission
mechanically coupled to first and second electric machines to transmit
power to an output member, the method comprising:
determining motor torque constraints for the first and second electric
machines;
determining battery power constraints for an electrical energy storage
device electrically connected to the first and second electric
machines;
determining a range for an additional torque input to the electro-
mechanical transmission; and
determining a preferred output torque to the output member of the
electro-mechanical transmission that is achievable within the motor
torque constraints, is achievable within the range of the additional
torque input, and is based upon the battery power constraints.
2. The method of claim 1, wherein the preferred output torque comprises a
commanded output torque to the output member in response an operator
torque request.
3. The method of claim 2, wherein the preferred output torque comprises a
maximum tractive torque to the output member.

4. The method of claim 2, wherein the preferred output torque comprises a
maximum regenerative torque to the output member.
5. The method of claim 1, wherein the additional torque input comprises an
engine input torque.
6. The method of claim 1, wherein the additional torque input comprises a
clutch reactive torque.
7. The method of claim 1, further comprising controlling operation of the
electro-mechanical transmission and the first and second electric
machines to achieve the preferred output torque at the output member
based upon the motor torque constraints, the range of the additional
torque input and the battery power constraints.
8. The method of claim 7, further comprising determining a preferred
output torque to the output member of the electro-mechanical
transmission that is achievable within the range of the additional torque
input and that minimizes a violation of a maximum battery power
constraint when the additional torque input is achievable within the
motor torque constraints and the additional torque input exceeds the
maximum battery power constraint.
9. The method of claim 7, further comprising determining a preferred
output torque to the output member of the electro-mechanical

transmission that is achievable within the range of the additional torque
input and is constrained by a maximum battery power constraint when
the additional torque input is achievable within the motor torque
constraints and the additional torque input is achievable within the
maximum battery power constraint.
10. The method of claim 7, further comprising limiting the preferred output
torque to the output member of the electro-mechanical transmission to an
output torque achievable within the motor torque constraints and
achievable within the battery power constraints.
11. The method of claim 10, wherein the maximum battery power constraint
comprises a maximum battery discharging power.
12. The method of claim 10, wherein the minimum battery power constraint
comprises a minimum battery charging power.
13. The method of claim 1, wherein the additional torque input comprises an
input torque to an input shaft from an internal combustion engine
mechanically coupled to the electro-mechanical transmission.
14. The method of claim 1, wherein the additional torque input comprises
torque transfer across an applied torque transfer clutch in the
transmission.

15. The method of claim 1, further comprising:
formulating mathematical equations representing maximum and
minimum motor torque constraints for the first and second electric
machines and representing maximum and minimum battery power
constraints;
formulating a mathematical equation representing the output torque;
formulating mathematical equations representing the range for the
additional torque input;
transforming the mathematical equations representing the maximum and
minimum battery power constraints to equations of concentric circles
having respective radii;
transforming the mathematical equations representing the maximum and
minimum motor torque constraints for the first and second electric
machines to equations comprising lines;
transforming the mathematical equations representing the range for the
additional torque input to equations comprising lines; and
transforming the mathematical equation representing the output torque to
an equation comprising a line.
16. The method of claim 15, further comprising:
determining at least one transformed achievable output torque based
upon the transformed motor torque constraints for the first and
second electric machines, the transformed battery power constraints,
and the transformed range for the additional torque input;

determining a transformed achievable maximum output torque from the
electro-mechanical transmission; and,
retransforming the transformed achievable maximum output torque to
determine preferred motor torques for the first and second electric
machines.
34
7. The method of claim 15, comprising calculating at least one intersection
of the transformed mathematical equations representing the maximum
and minimum battery power constraints, the transformed mathematical
equations representing the maximum and minimum motor torque
constraints for the first and second electric machines, the transformed
mathematical equations representing the range for the additional torque
input, and the transformed mathematical equation representing the output
torque.

A method for controlling an electro-mechanical transmission
mechanically coupled to first and second electric machines to transmit power
to an output member includes determining motor torque constraints and
battery power constraints. A preferred output torque to an output member is
determined that is achievable within the motor torque constraints, within a
range for an additional torque input and based upon the battery power
constraints.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=W5nevXRbiE8D8JOy0AtDmQ==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

269837

Indian Patent Application Number

1854/KOL/2008

PG Journal Number

46/2015

Publication Date

13-Nov-2015

Grant Date

10-Nov-2015

Date of Filing

31-Oct-2008

Name of Patentee

DAIMLER AG

Applicant Address

70546 STUTTGART,GERMAY A CORPORATION UNDER THE LAWS OF GERMANY

Inventors:

#	Inventor's Name	Inventor's Address
1	ANTHONY H HEAP	2969 LESLIE PARK CIRCLE ANN ARBOR, MICHIGAN 48105
2	TUNG-MING HSIEH	13055 TARKINGTON COMMON CARMEL, INDIANA 46033

PCT International Classification Number

B60K6/26; B60K6/365;H02P9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/984492	2007-11-01	U.S.A.