Powertrain control procedures

Abstract

A method for powertrain control, comprising: comparing a torque request from an operator with a powertrain torque control signal; locking a first reference torque at a first predetermined value while the torque request and the torque control signal differ by more than a predetermined amount; and controlling a torque based on a difference between the torque request and the first reference torque; characterized in that the first reference torque is locked to the first predetermined value while the torque request and the torque control signal differ by more than a predetermined amount, and the torque is an axle torque;wherein: (i) controlling the driveline torque based on the difference between the torque request and the first reference torque comprises: setting a threshold based on the difference between the torque request and the first reference torque; locking a second reference torque at a second predetermined value while the torque request and the torque control signal differ by more than the threshold; and controlling the axle torque based on a difference between the torque request and the second reference torque; and / or (ii) the method further comprises tracking the first reference torque to the axle torque while the torque request and the torque control signal do not differ by more than the predetermined amount.

Description

The present invention relates to a method for drive train control according to the preamble of claim 1, as is known in the art essentially from DE 10 2013 209 086 A1.Methods which are substantially comparable in type are evident from the publications DE 10 2018 103 687 A1 and DE 10 2010 051 221 A1.INITIATIONVehicles employ various propulsion systems in various configurations that generate and transmit tractive power to a driveline in response to an operator request. The accelerator pedal position and position changes are monitored and processed to provide torque requests that are accepted by the powertrain system. The changes in accelerator pedal position correspond approximately to the operator desired change in acceleration and, consequently, the axle torque requests. However, it is challenging to properly interpret the business of the accelerator pedal, and may lead to undesirable effects on drivability, particularly in systems that can cause large torque changes very rapidly (e.g., electric, hybrid, large diesel engine, boosted gasoline engine, etc.). Interpreting the changes in accelerator pedal position to accurately reflect the operator's true intention is a tedious task performed during vehicle development by iterative calibration sessions in the vehicle.SUMMARYAccording to the invention, a method for drive train control is presented, which is distinguished by the features of claim 1.In addition to one or more of the features described herein, controlling the axle torque based on the difference between the torque request and the first reference torque may include referencing a calibration library that relates the changes in torque to the rates of change in torque.In addition to one or more of the features described herein, controlling the axle torque based on the difference between the torque request and the second reference torque may include referencing a calibration library with the difference between the torque request and the second reference torque, the calibration library relating the changes in torque to the rates of change in torque.In addition to one or more of the features described herein, the calibration library may be delimited by a drive mode.In addition to one or more of the features described herein, the method may further include tracking the second reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the threshold.In addition to one or more of the features described herein, the method may further include retarding controlling powertrain torque based on the difference between the torque request and the second reference torque during an axle torque engagement, and subsequent to the axle torque engagement, initiating controlling powertrain torque based on the difference between the torque request and the second reference torque at an initial axle torque corresponding to a final axle torque at completion of the engagement.In addition to one or more of the features described herein, the first predetermined value may include an axle torque value that is present when the torque request and the torque control signal initially deviate by more than the predetermined amount.In addition to one or more of the features described herein, the second predetermined value may include an axle torque value that is present when the torque request and the torque control signal initially deviate by more than the threshold.Further, a vehicle will be described. The vehicle may include a powertrain system having at least one actuator for controlling an axle torque, and a control system having a control module including an instruction set executable to compare an operator torque request to a powertrain torque control signal, lock a first reference torque to a first predetermined value while the torque request and the torque control signal differ by more than a predetermined amount, the first predetermined value corresponding to an axle torque value present when the torque request and the torque control signal initially differ by more than a predetermined amount, set a threshold value based on the difference between the torque request and the first reference torque, lock a second reference torque to a second predetermined value while the torque request and the torque control signal differ by more than the threshold value, wherein the second predetermined value corresponds to an axle torque value that exists when the torque request and the torque control signal initially deviate by more than the threshold value, and to control the at least one actuator based on a difference between the torque request and the second reference torque.In addition to one or more of the features described herein, the controller of the at least one actuator based on the difference between the torque request and the second reference torque may include a reference to a calibration library with the difference between the torque request and the second reference torque, the calibration library relating the torque changes to the rates of change of the torque.In addition to one or more of the features described herein, the calibration library may be delimited by a drive mode.In addition to one or more of the features described herein, the instruction set may be further executable to track the first reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the predetermined amount.In addition to one or more of the features described herein, the instruction set may be further executable to track the second reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the threshold.In addition to one or more of the features described herein, the instruction set may be further executable to delay control of the at least one actuator based on the difference between the torque request and the second reference torque during an axle torque engagement and, subsequent to the axle torque engagement, initiate control of the at least one actuator based on the difference between the torque request and the second reference torque at an initial axle torque value corresponding to a final axle torque value at the completion of the engagement.In yet another exemplary embodiment, a method of powertrain control may include receiving, at a control module, accelerator pedal position from an accelerator pedal and vehicle speed information; calculating, at the control module, a driver torque target based on the accelerator pedal position and vehicle speed; calculating, at the control module, a deviation between the driver torque target and a shaped torque request; comparing, at the control module, the deviation to a first calibration threshold; locking, at the control module, a baseline reference torque to a first predetermined value while the deviation exceeds the first calibration threshold, the first predetermined value corresponding to the shaped torque request when the deviation initially exceeds the first calibration threshold; tracking, at the control module, the baseline reference torque of the shaped torque request while the deviation does not exceed the first calibration threshold, calculating at the control module a basic driver intent as the difference between the driver torque target and the basic reference torque, referencing at the control module a second calibration threshold as a function of the basic driver intent, comparing at the control module the deviation with the second calibration threshold, locking at the control module a true reference torque to a second predetermined value while the deviation exceeds the second calibration threshold, the second predetermined value corresponding to the shaped torque request when the deviation initially exceeds the second calibration threshold, tracking at the control module the true reference torque of the shaped torque request while the deviation does not exceed the second calibration threshold, calculating at the control module a true driver intent as the difference between the driver torque target and the true reference torque, referencing at the control module a library of calibration tables with the true driver intent and returning a torque acceleration request, the library of calibration tables relating the torque changes to the rates of change of torque, determining at the control module the shaped torque request based on the driver torque target bounded by the torque acceleration request, and controlling, by the control module, at least one actuator for controlling an axle torque based on the shaped torque request.In addition to one or more of the features described herein, the library of calibration tables may be delimited by a drive mode.The above features and advantages and other features and advantages of the disclosure will be readily apparent from the following detailed description when considered in connection with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSOther features, advantages, and details appear, by way of example only, in the following detailed description, wherein the detailed description refers to the drawings, in which: FIG. 1 illustrates an example powertrain system according to the present disclosure; FIG. 2 illustrates a functional block diagram of certain aspects of an example control system according to the present disclosure; FIG. 3 illustrates a process flow routine of an example powertrain controller according to the present disclosure; FIG. 4 illustrates example metrics in determining the basic driver intent, in accordance with the present disclosure; and FIG. 5 illustrates an example calibration vector according to the present disclosure.DETAILED DESCRIPTIONThe following description is merely exemplary in nature.Referring now to the drawings, wherein the illustrations are for the purpose of illustrating certain example embodiments only, FIG. 1 schematically illustrates a vehicle 100 including an example hybrid powertrain system 20 coupled to a driveline 60 and controlled by a control system 10. Like reference numerals refer to like elements throughout the specification. The powertrain system 20 includes torque-generating devices including an internal combustion engine 40 and a non-combustion torque machine 35 that are capable of generating torque and reacting to torque transmitted to the powertrain 60 via a transmission 50. One configuration of the powertrain system 20 may include the torque machine 35 mechanically rotatably coupled to a crankshaft 36 of the engine 40. The crankshaft may be rotatably mechanically coupled to an input member 51 of a multi-speed transmission 50 via a fluidic torque coupling device (torque converter) 55. The crankshaft 36 may be mechanically rotatably coupled to the torque machine 35 via a transmission mechanism 38. Other configurations of the powertrain system 20 including the torque machine 35 rotatably mechanically coupled to the engine 40 mechanically coupled to the transmission 50 may be used. Hybrid and non-hybrid powertrains may be employed in other embodiments including, for example, internal combustion powertrains, electric powertrains, and hybrid powertrains of any topology (e.g., serial, parallel, serial / parallel, mild, full, plug-in, BAS, multimode, etc.).The engine 40 is preferably a multi-cylinder internal combustion engine that converts the fuel into a mechanical torque through a thermodynamic combustion process. The engine 40 is equipped with a plurality of actuators and sensing devices for monitoring operation and supplying fuel to form a combustion charge to generate torque responsive to an operator request for vehicle propulsion. The actuators of the engine include slow actuators and fast actuators. A fast actuator is an actuator that completes a change in engine operation, e.g., an engine torque output responsive to a change in a command to the engine actuator, within a single engine cylinder event. An example of a fast engine actuator is spark ignition timing. A slow actuator is an actuator that completes a change in engine operation, e.g., an engine torque output responsive to a change in a command to the engine actuator, only after a delay of more than a single engine cylinder event. An example of a slow engine actuator is electronic throttle control (ETC). Due to latencies associated with intake manifold fill times and other factors, the engine may require 100-500 ms to cause a change in engine torque output in response to a change in ETC. The engine 40 is configured to execute auto-start and auto-stop control schemes and fuel-cut (FCO) control schemes during ongoing operation of the powertrain system 20. The engine 40 is considered to be in an OFF state when it is not rotating. The engine 40 is considered to be in an ON state when it is rotating, including one or more FCO states in which it is rotating and not being fueled.The combustionless torque machine 35 is an electrically-driven torque machine 35 that includes a multi-phase high voltage electric machine (i.e., a motor / generator) electrically connected to an inverter module 32. The torque machine 35 includes a rotor and a stator and an associated position sensor. The torque machine 35 is operable in coordination with the inverter module 32 to convert stored electrical energy to mechanical power and convert mechanical power to electrical energy. The inverter module 32 includes fast actuators that may complete a change in operation of the torque machine 35, e.g., a torque output or a speed output responsive to a change in a command to the engine actuator, within a time period corresponding to a single engine cylinder event, i.e., within 10-20 ms. Generally, the response time of an electrically driven torque machine 35 is many times faster than that of an internal combustion engine. An example of a fast actuator for the torque machine is a power transistor. The inverter module 32 acts as a fast actuator to control the torque machine 35. The electrical energy may be consumed or stored in a high voltage battery 25, in one embodiment.In one embodiment, the electrically-driven torque machine 35 includes an output member mechanically rotatably coupled to the crankshaft 36 of the engine 40 via the transmission mechanism 38 providing a mechanical power path therebetween. The transmission mechanism 38 may be configured to effect torque transfer between the engine 40 and the torque machine 35, including torque transfer from the torque machine 35 to the engine 40 for engine auto-start and auto-stop operation, tractive torque assist, torque transfer for vehicle regenerative braking, and torque transfer from the engine 40 to the torque machine 35 for high voltage electrical charging. In one embodiment, the transmission mechanism 38 may include a planetary gear set. In one embodiment, the engine 40 may include a low voltage solenoid-operated electric starter 39 for starting the engine in response to a key-crank event.The high voltage battery 25 is electrically connected to the inverter module 32 via a high voltage DC bus 29 to transmit high voltage DC electrical power to the torque machine 35 in response to control signals generated in the control system 10. The inverter module 32 is electrically connected to the torque machine 35 via a polyphase motor control power bus 31. The inverter module 32 is configured with suitable control circuits that include power transistors, e.g., IG-BTs, for transforming high voltage DC electrical power into high voltage AC electrical power and for transforming high voltage AC electrical power into high voltage DC electrical power. The inverter module 32 preferably uses pulse width modulation (PWM) control to convert the stored DC power from the high voltage battery 25 to AC electrical power to drive the torque machine 35 to generate torque in response to motor torque commands. Similarly, in response to motor control commands including as part of a regenerative control strategy, the inverter module 32 converts the mechanical power transferred to the torque machine 35 into DC electrical power to generate electrical energy storable in the high voltage battery 25. The inverter module 32 is configured to control the power transistors to provide the motor drive and regeneration functionality in response to the motor control commands. In one embodiment, a DC / DC electrical power converter 34 is electrically connected to a low voltage bus 28 and a low voltage battery 27 and electrically connected to the high voltage bus 29. Such electrical power connections are known and will not be described in detail. The low voltage battery 27 is electrically connected to an auxiliary power system 45 to provide low voltage electrical power to low voltage systems in the vehicle including, for example, power windows, HVAC blowers, seats, and the low voltage solenoid-operated electric starter 39.The transmission 50 is configured to operate in one of a plurality of selectable fixed gear modes to operate at a gear ratio that achieves a preferred match between the operator demand for propulsion and an engine operating point, and preferably uses one or more differential gears and hydraulically activated clutches to effect torque transfer in one of a plurality of selectable modes over a range of speed ratios between the input member 51 and the output member 62. Example transmissions include, by way of example, an automatic transmission, a dual clutch transmission, a clutchless transmission, and a manual transmission. The transmission 50 performs upshifts to shift to a lower numerical multiplication ratio (gear ratio) mode and performs downshifts to shift to a higher numerical multiplication ratio mode in response to output torque requests. An upshift of the transmission requires a reduction in engine speed so that at a gear ratio associated with the target mode, the engine speed corresponds to the transmission output speed multiplied by the gear ratio. A transmission downshift requires an increase in engine speed so that at a gear ratio associated with the target mode, the engine speed corresponds to the transmission output speed multiplied by the gear ratio. Alternatively, the transmission 50 may be configured as a continuously variable transmission. The transmission preferably includes a first rotational position / speed sensor 52 to monitor rotation of the input member 51 and a second rotational position / speed sensor 54 to monitor rotation of the output member 62 of the transmission 50. The vehicle speed is easily determined from the second rotational position / speed sensor 54 and a final drive ratio (e.g., 65, 66). The powertrain system 20 may include a torque converter 55 between the engine 40 and the transmission 50.Driveline 60 may include a differential gear device 65 mechanically coupled to an axle 64, a transaxle, or a half shaft mechanically coupled to a wheel 66, in one embodiment. Driveline 60 transfers tractive power between transmission 50 and a road surface.The control system 10 may include a control module 12 signally connected to an operator interface 14. The control module 12 preferably includes a plurality of discrete devices co-located with the individual elements of the powertrain system 20 to perform operational control of the individual elements of the powertrain system 20. The control module 12 may also include a controller that provides hierarchical control of other controllers. The control module 12 is signally and operatively connected to both the high voltage battery 25, the inverter module 32, the torque machine 35, the engine 40, and the transmission 50 either directly or via a communication bus 18 to monitor their operation and determine their parametric states. The operator interface 14 of the vehicle 100 is a controller signally connected to a plurality of human / machine interface devices through which a vehicle operator inputs various operator requests for propulsion or tractive effort and other requests for operation of the vehicle 100. The human / machine interface devices are devices that monitor and evaluate operator demand for tractive effort including, for example, an accelerator pedal 112 that provides an operator accelerator pedal position (operator APP); a brake pedal 113 that provides an operator brake pedal position (operator BPP); a transmission range selector 114 that provides an operator demanded transmission range signal (PRNDL); and a vehicle speed cruise control system 116 that provides an operator demand for vehicle speed (CRUISE). Other human / machine interface devices preferably include an ignition switch to enable an operator to initiate operation of the vehicle, including starting and starting the engine 40, a steering wheel, and a headlight switch. The human / machine interface devices set forth herein are exemplary. It is also recognized that not all vehicles may include many of the human / machine interface devices. For example, autonomous and semi-autonomous vehicles may include fewer or other human / machine interface devices. The transmission range selector 114 provides a signal input indicative of the direction of operator-demanded motion of the vehicle including a discrete number of operator-selectable positions indicative of the preferred rotational direction of the output member 62 of either a forward or a reverse direction or a neutral condition. It will be appreciated that the vehicle may still move in a direction other than the indicated direction of operator demand movement due to a rollback caused by the location of a vehicle, e.g., on a hill.The powertrain system 20 includes a communication scheme including the communication bus 18 for carrying out communications in the form of sensor signals and actuator command signals between the control system 10 and the elements of the powertrain system 20. The communication scheme uses one or more communication systems and devices, e.g., communication bus 18, a direct connection, a local area network bus, a serial peripheral interface bus, and wireless communications to perform the information transfer.Throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Control module, module, controller, controller, controller, electronic controller, processor, and similar terms as used herein mean any one or various combinations of one or more application specific integrated circuit(s) (ASIC), electronic circuit(s), central processing unit(s) (preferably microprocessor(s)) and associated data memory and memory (read only memory (ROM), random access memory (RAM), electrically programmable read only memory (EPROM), hard disk drive, etc.), or microcontrollers that execute one or more software or firmware programs or routines, combinational logic circuit(s), input / output circuitry and devices (I / O), and suitable signal conditioning and buffer circuitry, a high speed clock, analog-to-digital (A / D) and digital-to-analog (D / A) circuitry and other components to provide the described functionality. A control module may include various communication interfaces including point-to-point or discrete lines and wired or wireless interfaces to networks including wide area networks and local area networks, vehicle controller area networks, and in-house and service-related networks. The functions of the control module as set forth in this disclosure may be performed in a distributed control architecture among multiple networked control modules. Software, firmware, programs, instructions, routines, code, algorithms, and similar terms mean any controller-executable instructions that include calibrations, data structures, and look-up tables. A control module includes a set of control routines that are executed to provide the described functions. The routines are executed, such as by a central processing unit, and are operable to monitor inputs from sensing devices and other networked control modules and execute control and diagnostic routines to control operation of the actuators. The routines may be executed at regular intervals during ongoing engine and vehicle operation. Alternatively, the routines may be executed in response to the occurrence of an event, software calls, or request via user interface inputs or requests.FIG. 2 illustrates a functional block diagram of certain aspects of an example control system 10. The driver axle torque module 200 may determine a final driver axle request, as discussed below.The driver axle torque module 200 may include a pedal request module 202, a translation module 210, a torque request arbitration module 222, a torque acceleration request module (TRM) 203, and a torque shaping module 224. The pedal request module 202 determines a pedal torque request (PTR). The pedal torque request may occur with respect to a range of drive torque (i.e., torque at the crankshaft or other input to the driveline). The pedal request module 202 may determine the pedal torque request based on the accelerator pedal position APP 205 and the vehicle speed information 207, among other suitable parameters, as known to those skilled in the art.The conversion module 210 receives the pedal torque request and converts the pedal torque request to the axle torque range (i.e., the torque at the wheels or axles). After the request is placed in the axle torque range, it may be referred to as a driver torque request. The conversion module 210 may convert the pedal torque request based on, e.g., driveline losses, the transmission gear ratio selected within the transmission, one or more torque ratios, and other suitable parameters.Arbitration module 222 may receive and relay the driver torque request and other torque requests 225 between the received requests. For example only, arbitration module 222 may mediate torque requests relating to longitudinal propulsion, such as driver torque requests and cruise speed torque requests. Arbitration module 222 outputs a winner of such arbitrations. In one embodiment, arbitration between prime mover torque requests and other torque requests that are not primarily for prime mover purposes, e.g., chassis control interventions such as stability controls, may result in bypassing the torque acceleration request module 203 at 223 for torque scheduling according to alternative controls and calibrations. In other embodiments, arbitrations between prime mover torque requests and other torque requests that are not primarily for prime mover purposes may be performed in other modules. The output of the arbitration module is the winner of the arbitration and represents a raw axle torque request (e.g., Nm) and may be referred to as a driver torque target (DTT). The raw axle torque request occurs with respect to the axle torque range (i.e., the torque at the wheels or axles). The driver torque target DTT may be acted upon by the torque acceleration request module (TAMM) 203, as further described herein.The torque acceleration request module (TRM) 203 may receive the raw axle torque request in the driver torque target DTT from the arbitration module 222. The torque acceleration request module 203 may use one or more calibration tables or maps that relate the axle torque requests to form the raw axle torque requests into a formed torque request (STR) with torque rate limits, as will be described in further detail herein. In particular, the calibration tables may relate a desired change in axle torque to a desired rate of change in axle torque to achieve vehicle acceleration behavior in accordance with a desired acceleration behavior. It will be appreciated that herein the calibrations and discussion are in the torque range, and particularly in the axle torque range; however, vehicle performance / drivability development may initially take place in an acceleration range that is later translated into an axle torque range for application of the controls, recognizing that one of ordinary skill in the art understands the relationships between vehicle acceleration and axle torque. A calibration table as used herein may refer to calibration elements, calibration arrays, calibration tables, or combinations and libraries thereof. A calibration table as described may be adapted for varying drive styles or conditions (drive modes), e.g., tour, sport, snow, locked distance, all-wheel drive low or high, etc. As such, a multi-dimensional library of such calibration tables may be bounded by a drive mode dimension, and accessed in accordance therewith. Therefore, the torque acceleration request module (TRM) 203 may include additional input at 211, e.g., through user interface selection, to selectively use a table corresponding to the selected drive mode. The torque acceleration request module (TRM) 203 may shape the torque acceleration request, e.g., according to the rate limits of the calibration table and one or more filters, to reduce or prevent a "erratic" or "jerky" feel that may be experienced when the driver shows accelerator pedal business or churniness. Generally, torque shaping is implemented to improve drivability and provide a comfortable, smooth, and responsive experience of the driver without being perceptibly constrained. The torque acceleration request module (TRM) 203 may provide the shaped torque request (STR) to the additional torque shaping module 224, as described in further detail herein.The shaping module 224 may receive the shaped torque request (STR) and provide additional torque shaping. In powertrains that may distribute total axle torque to different axles or individual vehicle corners, shaping module 224 may further adjust the shaped torque request (STR) for such distribution, merely by way of example. The shaped torque request STR occurs with respect to the axle torque range (i.e., the torque at the wheels or axles). The shaped torque request STRis forwarded to the torque delivery module 226 and represents the current delivered or controlled axle torque.The torque delivery module 226 receives the shaped torque request STR from the shaping module 224. The torque delivery module 226 determines a final driver axle request and may include an axle torque arbitration module 228 for arbitration with other axle torque requests. The axle torque arbitration module 228 arbitrates between the shaped torque request STR from the shaping module 224 and other axle torque requests and axle torque interventions 240. In one embodiment, axle torque interventions may be accommodated by levitation or retarding execution of the shaped torque request STRsuch that upon completion of any such intervention, the shaped torque request STRis initiated with an axle torque corresponding to the axle torque upon completion of the axle torque intervention. The axle torque interventions may come from driveline dynamic management (DDM), which is primarily used for so-called snap zone or lash zone management, to mitigate, for example, undesirable driveline gear engagement disturbances (i.e., operator perceptible noise and shock) during torque reversals or applications from rest conditions. Other axle torque interventions may also include a torque reduction requested by a traction control system when positive wheel slip is detected. Positive wheel slip may occur when axle torque (i.e., the torque for the wheels) overcomes the friction between the wheels and the road surface and the wheels slip forward with respect to the road surface. The other axle torque interventions may also include a torque increase request to counteract negative wheel slip, where a tire of the vehicle slips or drags with respect to the road surface in a reverse direction because the axle torque is negative. Other axle torque interventions may also include various brake management requests and other powertrain axle torque affecting controls related to, for example, vehicle stability and lane following management, collision avoidance, initial collision mitigation, and preparations. These example other axle torque requests and interventions are disclosed as examples only. Therefore, the torque delivery module 226 may set the final driver axle request (e.g., Nm) generally equal to the shaped torque request STR unless another axle torque request or higher priority axle torque intervention is required. The final driver axle request is forwarded to the actuation module 250.The actuation module 250 receives the final driver axle request from the torque delivery module 226. The actuation module 250 determines how the final driver axle request is achieved. The actuation module 250 may be powertrain specific. Actuation module 250 may be implemented differently for spark-ignition engines as compared to compression-ignition engines and for electric work machines in hybrid and full electric powertrains, or use other control schemes, for example only. In a spark ignition engine, actuation module 250 may vary, by way of example only, the opening of a throttle as a slow actuator that allows a wide range of torque control. The actuation module 250 may deactivate cylinders using a cylinder actuator module that may also provide a wide range of torque control, but may also be slow and may include driving behavior and emissions concerns. The actuation module 250 may use spark timing as a fast actuator. However, spark timing may not provide as large a range of torque control. In addition, the amount of torque control possible with changes in spark timing (referred to as spark reserve capacity) may vary as the air flow changes. All-electric vehicles would require the actuation module to regulate the motor torque(s) primarily through an inverter controller, which may vary the torque quickly and predictably. In various implementations, such as the hybrid embodiment of FIG. 1, the actuation module 250 may employ various controls of engine actuators and electric machine actuators (e.g., inverters) to perform the axle torque control.FIG. 3 illustrates a process flow routine (routine) 300 of an example implementation of the torque acceleration request module (TRM) 203 (FIG. 2 ) and the controller of the powertrain system 20 (FIG. 1 ). The various steps shown in routine 300 may be embodied in executable code within control module 12 of FIG. 1. During ongoing vehicle operation, routine 300 is repeatedly executed as part of overall control of powertrain system 20. The illustrated steps may be performed in the illustrated order and manner, or may be performed in alternative orders or concurrently, with routine 300 being exemplary. Routine 300 is entered at 301, including receiving various input information required for the following operations, e.g., accelerator pedal position APP 205 and vehicle speed information 207 (FIG. 2 ), and the control parameter, such as shaped torque request STR of present routine 300. The driver torque target DTT is next calculated at 305 and may include implementations of pedal torque requests into the axle torque range and arbitrations of the pedal torque request and other torque requests to arrive at the driver torque target DTT. The amount of deviation of the driver torque target DTT from the shaped torque request STR is next calculated at 307. The shaped torque request STR, as previously mentioned, can be expected to attenuate high rates of change in accordance with certain time constant constraints, yet generally approach its output (STR) to the input (DTT). Thus, deviations between the shaped torque request STR and the driver torque target DTT may be expected at higher rates of change of the driver torque target DTT and may remain until the shaped torque request STR and the driver torque target DTT converge.At 309, the deviation is compared to a first calibration threshold K1representing a predetermined minimum torque change threshold sufficient to lock a historical data set of the current input axle torque at or about the occurrence of the minimum torque change threshold. In one embodiment, the calibration threshold K 1 may be an element. In other embodiments, the calibration threshold may be vector or table derived. The shaped torque request STR is representative of the currently supplied axle torque. Thus, at 311, if the deviation exceeds the calibration threshold K 1, a baseline reference torque (BRT) may be locked to the shaped torque request value STR corresponding to the time of the deviation. In other embodiments, the locked value may deviate from the shaped torque request by, for example, some constant offset. The basic reference torque BRT remains locked at this value as long as the deviation exceeds the calibration threshold value K 1. If the deviation no longer exceeds the calibration threshold K1or as long as the deviation does not exceed the calibration threshold K1, at 313 the basic reference torque BRT folgt the shaped torque request STR. A basic driver intent BDI is calculated at 315 as the difference between the driver torque target DTT and the basic reference torque BRT. It is recognized that while the baseline reference torque BRT remains locked, the baseline driver intent BDI remains a metric of the operational history in the locked value of the shaped torque request STR from the latest deviation of the driver torque target DTT from the shaped torque request STR that exceeds the calibration threshold K 1. Consequently, it is recognized that the basic driver intent BDI provides a metric related to a temporal history that accounts for operation and represents a basic change in desired acceleration. The basic driver intent BDI therefore provides a metric that includes historical control information (e.g., the locked basic reference torque BRT), current control information (e.g., the shaped torque request STR), and future control information (e.g., the driver torque target DTT).FIG. 4 illustrates two exemplary sequences of locking and releasing the basic reference torque BRT; one sequence "A" takes place with respect to releasing the accelerator pedal, while another sequence "B" takes place with respect to depressing the accelerator pedal. In FIG. 4, the torque (TQ) is along the vertical axis, while the time (t) is along the horizontal axis. The driver torque target DTT is the solid line labeled 403, the shaped torque request STR is the dotted line labeled 405, the baseline reference torque BRT is the dashed line labeled 407, and the baseline driver intent BDI is shown as the double arrows labeled 409. Prior to time t 1, the shaped torque STR and the reference basic torque BRT follow exactly because the driver torque target DTT and the shaped torque request STR do not deviate more than the calibration threshold K 1 even when tip-out begins, as shown by the decreasing driver torque target DTT. At time t 1, the driver torque target DTT and the shaped torque request STR deviate by more than the calibration threshold K 1, locking the baseline reference torque BRT to the then current shaped torque request STR. The basic reference torque BRT remains locked between the times t 1 and t 2. At time t 2, the driver torque target DTT and the shaped torque request STR deviate no longer by more than the calibration threshold K 1, unlocking the baseline reference torque BRT and tracking the shaped torque request STR again. After time t 2, moderate pedal pressure begins, as shown by increasing driver torque target DTT. The shaped torque request STR and the basic reference torque BRT are exactly following, since the driver torque target DTT and the shaped torque request STR deviate by no more than the calibration threshold K 1. At time t 3, the driver torque target DTT and the shaped torque request STR deviate by more than the calibration threshold K 1, locking the baseline reference torque BRT to the then current shaped torque request STR. The basic reference torque BRT remains locked between the times t 3 and t 4. At time t 4, the driver torque target DTT and the shaped torque request STR deviate by no more than the calibration threshold K 1, unlocking the basic reference torque BRT and following the shaped torque request STR again.It will be appreciated that the basic driver intent BDI may vary significantly because the driver torque target DTT remains dynamic and variable in accordance with the change in the accelerator pedal, and particularly while the basic reference torque BRT remains locked and does not follow the shaped torque request STR in its tendency to converge with the driver torque target DTT. The basic driver intent BDI is next used at 317 to reference a second calibration threshold K2 that can be referenced from a calibration table to return, for each basic driver intent BDI, a respective second calibration threshold K2 that represents a predetermined minimum torque change threshold sufficient to lock a historical data set of currently supplied axle torque at or about the occurrence of the minimum torque change threshold. In one embodiment, the table referenced for the second calibration threshold K2may be a one-dimensional vector. Other embodiments may use multi-dimensional calibration tables or calibration libraries. The shaped torque request STR is representative of the currently supplied axle torque. An exemplary calibration vector is illustrated in FIG. 5. It is recognized that the second calibration threshold K 2 may change as the basic driver intent BDI changes. At 319, the deviation (i.e., the deviation between the shaped torque request STR and the driver torque target DTT) is compared to the second calibration threshold K 2. Thus, if the deviation exceeds the second calibration threshold K 2, a true reference torque (TRT) may be locked at 321 to the shaped torque request value STR corresponding to the time of the deviation. In other embodiments, the locked value may deviate from the shaped torque request by a constant offset, for example. The true reference torque TRT remains locked at this value as long as the deviation exceeds the second calibration threshold K2. If the deviation no longer exceeds the second calibration threshold K2or as long as the deviation does not exceed the second calibration threshold K2, the true reference torque TRT folgt the shaped torque request STRat 323. A true driver intent TDI is calculated at 325 as the difference between the driver torque target DTT and the true reference torque TRT. It is recognized that while the true reference torque TRT remains locked, the true driver intent TDI maintains a metric of the operational history in the locked value of the shaped torque request STR from the latest deviation of the driver torque target DTT from the shaped torque request STR of more than the second calibration threshold K 2. Thus, it is recognized that the true driver intent TDI provides a metric related to a temporal history that accounts for operation that changes with the changes in the basic driver intent BDI and represents a true change in desired acceleration that relates to the historical operation in time and torque that is increasingly closer to current operation. The true driver intent TDI therefore provides a metric that includes historical control information (e.g., the locked true reference torque TRT), the current control information (e.g., the shaped torque request STR), and the future control information (e.g., the driver torque target DTT).At 327, a torque acceleration request library, TAR library, is referenced to look up a torque acceleration request value, TAR value, corresponding to the true driver intent TDI. The library may contain a plurality of, for example, one-dimensional tables each corresponding to a specific drive mode as previously described. In one embodiment, the torque acceleration request value, TAR value, may represent a rate limit for the changes in axle torque. It will be appreciated that such control by looking up based on the true driver intent TDI as it varies with changes in the basic driver intent BDI may smooth the final transition phase of the changes in acceleration by effectively damping or cushioning the rate of change of acceleration toward the final acceleration driver torque target DTT. The final shaping of the shaped torque request STR at 329 may operate to limit the rate of the driver torque target DTT in the course of the shaping functions and filtering at 329, which may include a further adjustment of the shaped torque request, as may be advantageous in distributing the total axle torque between multiple axles or vehicle corners. The torque delivery and actuation functions of the modules 226 and 250 of FIG. 2 are implemented in controlling the powertrain system according to the shaped torque request STR at 331. Routine 300 terminates at 333, re-entering, e.g., at 301, for iterative execution.When a relationship between first and second elements is described in the above disclosure, unless expressly described as "direct", this relationship may be a direct relationship in which no other intervening elements are present between the first and second elements, but may also be an indirect relationship in which one or more intervening elements (either spatially or functionally) are present between the first and second elements.

Claims

A method for powertrain control, comprising: comparing an operator torque request with a powertrain torque control signal; locking a first reference torque to a first predetermined value while the torque request and the torque control signal differ by more than a predetermined amount; and controlling a torque based on a difference between the torque request and the first reference torque; characterized in that the first reference torque is locked to the first predetermined value while the torque request and the torque control signal differ by more than a predetermined amount, and that the torque is an axle torque; wherein: (i) controlling the powertrain torque based on the difference between the torque request and the first reference torque comprises: setting a threshold value based on the difference between the torque request and the first reference torque; locking a second reference torque to a second predetermined value while the torque request and the torque control signal deviate by more than the threshold; and controlling the axle torque based on a difference between the torque request and the second reference torque; and / or (ii) the method further comprises tracking the first reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the predetermined amount.The method of claim 1, wherein controlling the axle torque based on the difference between the torque request and the second reference torque comprises referencing a calibration library with the difference between the torque request and the second reference torque, the calibration library relating the changes in torque to the rates of change in torque.The method of claim 2, wherein the calibration library is delimited by a drive mode.The method of claim 1, further comprising tracking the first reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the predetermined amount.The method of claim 1, further comprising: tracking the second reference torque to the axle torque while the torque request and the torque control signal deviate by no more than the threshold.The method of claim 1, further comprising: delaying controlling the powertrain torque based on the difference between the torque request and the second reference torque during an axle torque engagement; and subsequent to the axle torque engagement, initiating controlling the powertrain torque based on the difference between the torque request and the second reference torque at an initial axle torque corresponding to a final axle torque at completion of the engagement.

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