CROWDED CONTROL FOR HYBRID ELECTRIC VEHICLES

Abstract

Vehicle, including the following: a drive train with an electric machine that is driven by a turbine wheel of a torque converter; and a control unit configured to instruct the electric machine to provide torque to the impeller in response to a vehicle speed of zero and a brake pedal released beyond a limit position, wherein the torque is a predetermined feed-forward torque adapted by a feedback torque based on a difference between measured and calculated rotational speeds of the electric machine, the feed-forward torque being based on the inertia of the impeller.

Description

AREA OF INVENTION

[0001] The present disclosure relates to creep control in hybrid electric vehicles (HEVs). STATE OF THE ART

[0002] A hybrid electric drive comprises a drive system and an electric machine. The torque (or power) generated by the drive system and / or the electric machine can be transmitted to the driven wheels via a transmission to propel the vehicle. A traction battery supplies the electric machine with energy. The prior art in this regard is disclosed in documents DE 10 2015 113 573 A1, DE 10 2013 224 995 A1, DE 10 2013 104 514 A1, DE 10 2015 117 563 A1 and DE 10 2014 221 014 A1. SUMMARY

[0003] According to one embodiment, a vehicle comprises a drive system and a transmission. The transmission includes a torque converter with an impeller. The vehicle further comprises an electric machine configured to provide drive torque to the impeller. The impeller is selectively coupled to the drive system via a clutch. At least one vehicle control unit is configured to instruct the electric machine to provide torque to the impeller in response to the drive system being set to OFF, the transmission being set to DRIVE, a vehicle speed of zero, and a brake pedal released beyond a limit position. The torque is a predetermined feed-forward torque adjusted by a feedback torque based on the difference between measured and calculated rotational speeds. The rotational speeds are the rotational speeds of the electric machine.The feed-forward torque is based on the inertia of the impeller.

[0004] In another embodiment, a vehicle comprises a drive system in which an electric machine is driven by the impeller of a torque converter. The vehicle also includes a control unit configured to instruct the electric machine to supply torque to the impeller in response to a zero vehicle speed and a brake pedal released beyond a limit position. This torque is a predetermined feed-forward torque adjusted by a feedback torque based on the difference between measured and calculated rotational speeds. The feed-forward torque is based on the impeller's inertia.

[0005] In yet another embodiment, a method for restarting a torque converter impeller connected to an electric machine is presented. The method comprises instructing the electric machine to supply torque to the impeller in response to a zero vehicle speed and a brake pedal released beyond a limit position. This torque is a predetermined feed-forward torque that is adjusted proportionally to a difference between measured and calculated electric machine speeds. The feed-forward torque is based on the impeller's inertia. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of an exemplary HEV. Fig. Figure 2 is a diagram illustrating rotational speeds for an example impeller / motor controlled by feedback control. Fig. Figure 3A is a diagram illustrating rotational speeds for an exemplary electric machine controlled by feed-forward and feedback controls. Fig. 3B is a diagram showing the speed deviation of the electric machine from the example in Fig. 3A illustrates this. Fig. 3C is a diagram that illustrates the electric machine from the example in Fig. 3A connected torques illustrated. Fig. Figure 4 is a flowchart illustrating an algorithm for controlling motor / generator speed in a HEV according to an embodiment of the present disclosure. Fig. Figure 5 illustrates a control unit for controlling motor / generator speed during rotation of the impeller using feed-forward and feedback controls. DETAILED DESCRIPTION

[0006] Embodiments of the present disclosure are described below. It is understood, however, that the disclosed embodiments are only examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of certain components. Therefore, the structural and functional details disclosed herein should not be interpreted as limiting, but rather as a representative basis intended to suggest to those skilled in the art the different uses of the embodiments. Those skilled in the art will understand that various features illustrated and described with reference to one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not expressly illustrated or described.The combinations of illustrated features provide representative embodiments for typical applications. However, different combinations and modifications of the features in accordance with the teachings of this disclosure may be desirable for certain applications or implementations.

[0007] With reference to Fig. Figure 1 illustrates a schematic representation of a hybrid electric vehicle (HEV) 10 according to an embodiment of the present disclosure. Fig. Figure 1 illustrates representative relationships between the components. The physical placement and orientation of the components within the vehicle may vary. The HEV 10 comprises a drive 12 with a drive system 14 that drives a transmission 16, which can be referred to as a modular hybrid transmission (MHT). As described in more detail below, a transmission 16 comprises an electric machine, such as an electric motor / generator (M / G) 18, an associated traction battery 20, a torque converter 22, and a multi-stage automatic transmission or gearbox 24.

[0008] The drive system 14 and the M / G 18 are both power sources for the HEV 10. The drive system 14 generally represents a power source that may include an internal combustion engine, such as one powered by gasoline, diesel, or natural gas, or a fuel cell. The drive system 14 generates engine power and a corresponding drive torque, which is provided to the M / G 18 when a disengagement clutch 26 between the drive system 14 and the M / G 18 is at least partially engaged. The M / G 18 can be implemented as any type of a wide variety of electric machine types. For example, the M / G 18 can be a permanent magnet synchronous motor. The power electronics 56 conditions the direct current (DC) supplied by the battery 20 to meet the requirements of the M / G 18, as described below. For example, the power electronics can supply three-phase alternating current (AC) to the M / G 18.

[0009] When the release clutch 26 is at least partially engaged, power flows from the drive system 14 to the M / G 18. Power flow from the M / G 18 to the drive system 14 is also possible. For example, the release clutch 26 can be engaged and the M / G 18 can function as a generator to convert rotational energy provided by a crankshaft 28 and M / G shaft 30 into electrical energy to be stored in the battery 20. The release clutch 26 can also be disengaged to isolate the drive system 14 from the rest of the drivetrain 12, allowing the M / G 18 to serve as the sole power source for the HEV 10. The shaft 30 runs through the M / G 18. The rotor 19 of the M / G 18 is attached to the shaft 30, whereby the drive system 14 is selectively connected to the shaft 30 only when the release clutch 26 is at least partially engaged.

[0010] The M / G 18 is drive-connected to the torque converter 22 via the shaft 30. For example, the torque converter housing can be attached to the shaft 30. The torque converter 22 is therefore drive-connected to the drive system 14 when the release clutch 26 is at least partially engaged. Two components are drive-connected when they are connected by a power flow path that forces their rotational speeds to be directly proportional. The torque converter 22 comprises an impeller 35, which is attached to the torque converter housing (and thus to the rotor 19), and a turbine 37, which is attached to a transmission input shaft 32. The torque converter 22 provides a hydraulic coupling between the shaft 30 and the transmission input shaft 32. The torque converter 22 transmits power from the impeller 35 to the turbine 37 when the impeller rotates faster than the turbine.The magnitude of the turbine torque and the impeller torque generally depend on the relative rotational speeds. If the ratio between impeller speed and turbine speed is sufficiently high, the turbine torque will be a multiple of the impeller torque. A torque converter bypass clutch 34 can be provided to, upon engagement, frictionally or mechanically couple the impeller and turbine of the torque converter 22, enabling more efficient power transmission. The torque converter bypass clutch 34 can be operated as a launch clutch to allow seamless vehicle start-up. Alternatively, or in combination with this, a launch clutch similar to the disengagement clutch 26 can be provided between the M / G 18 and the gearbox 24 for applications that do not provide a torque converter 22 or a torque converter bypass clutch 34.In some applications, the release clutch 26 is generally referred to as an upstream clutch, and the starting clutch 34 (which may be a torque converter bypass clutch) is generally referred to as a downstream clutch.

[0011] The gearbox 24 can include gear sets (not shown) that are selectively positioned in different gear ratios by the selective engagement of friction elements such as clutches and brakes (not shown) to establish the desired multiple discrete or stepped drive ratios. The friction elements are controllable via a switching scheme that connects and disconnects specific elements of the gear sets to control the ratio between a gearbox output shaft 38 and the gearbox input shaft 32. The gearbox 24 is automatically shifted from one ratio to another based on various vehicle and environmental operating conditions by an associated control unit, such as a powertrain control unit (PCU) 50. The gearbox 24 then provides drivetrain output torque to the output shaft 38. The output shaft 38 can be connected to a drivetrain 37 (e.g., a transmission, a powertrain, or a powertrain).a drive shaft and joint pieces) which connects the output shaft 38 to the differential 40.

[0012] It will be understood that the hydraulically controlled gearbox 24 used with a torque converter 22 is only one example of a gearbox or gearbox arrangement; any multi-stage gearbox that accepts input torque(s) from a drive system and / or a motor and then provides torque to an output shaft at the various gear ratios is acceptable for use with embodiments of the present disclosure. For example, gearbox 24 can be implemented by an automated mechanical (or manual) shifting transmission (AMT) comprising one or more servo motors to translate / rotate the shift forks along a shift rail to select the desired gear ratio. As is generally understood by those skilled in the art, an AMT can be used, for example, in applications with higher speed requirements.

[0013] As in the representative embodiment in Fig. As shown in Figure 1, the output shaft 38 can be connected to a drivetrain 37, which connects the output shaft 38 to the differential 40. The differential 40 drives a pair of wheels 42 via their respective axles 44, which are connected to the differential 40. The differential transmits approximately the same torque to each wheel 42 while allowing slight differences in rotational speed, for example, when a vehicle turns a corner. Various types of differentials or similar devices can be used to distribute torque from the drive to one or more wheels. In some applications, the torque distribution may vary, for example, depending on the operating mode or operating condition in question.

[0014] While the control unit is depicted as a single unit, the control unit 50 can be part of a larger control system and be controlled by various other control units in the vehicle 10, such as a vehicle system controller (VSC) and a battery control module (BECM). It will be understood that the powertrain control unit 50 and one or more control units together can be referred to as a "control unit" that controls various actuators in response to signals from different sensors to control functions such as starting / stopping the drive system 14, operating the motor / gear unit 18 to provide wheel torque or charge the battery 20, selecting or terminating transmission shifts, and so on. The control unit 50 may include a microprocessor or a central processing unit (CPU) communicating with various types of computer-readable storage devices or media.Computer-readable data storage devices or media can include volatile and non-volatile memory, such as ROM, RAM, and keep-alive memory (KAM). KAM is a permanent or non-volatile memory that can be used to store various operating variables while the CPU is powered off. Computer-readable storage devices or media can be implemented using any number of known storage devices, such as PROMs (programmable read-only memory), EPROMs (electrical PROMs), EEPROMs (electrically erasable PROMs), flash memory, or any other electrical, magnetic, optical, or combination storage devices capable of storing data, including data representing executable instructions used by the control unit to control the propulsion system, traction battery, transmission, or other vehicle systems.

[0015] The control unit communicates with various drive system / vehicle sensors and actuators via an input / output (I / O) interface, which can be implemented as a single integrated interface providing various raw data or signal conditioning, processing and / or conversion, short-circuit protection, etc. Alternatively, one or more dedicated hardware or firmware chips can be used to condition and process certain signals before they are provided to the CPU. As generally described in the representative embodiment in Fig. As illustrated in Figure 1, the control unit 50 can communicate signals to and / or from the drive system 14, release clutch 26, M / G 18, the starting clutch 34, gearbox 24, and power electronics 56. Although not explicitly shown, experts will recognize various functions or components that can be controlled by the control unit 50 within each of the aforementioned subsystems.Representative examples of parameters, systems and / or components that can be actuated directly or indirectly by means of control logic executed by the control unit include timing, rate and duration of fuel injection, position of the throttle valve, timing of ignition core (in spark-ignition engines), timing and duration of intake / exhaust valve, components of the front-end accessory drive (FEAD) such as alternator, air conditioning compressor, battery charging, regenerative braking, M / G operation, clutch pressure for release clutch 26, starting clutch 34 and gearbox 24, etc.Sensors that communicate inputs via the I / O interface can be used to display, for example, turbocharger boost pressure (if applicable), crankshaft position (PIP), engine speed (RPM), wheel speed (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), manifold absolute pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle position (TP), ambient air temperature (TMP), exhaust oxygen concentration (EGO) or any other exhaust component concentration or presence, intake air flow (MAF), transmission ratio, gear or mode, transmission oil temperature (TOT), transmission turbine speed (TS), torque converter bypass clutch 34 status (TCC), deceleration or shift mode (MDE).

[0016] Control logic or functions executed by the control unit 50 can be represented by flowcharts or similar diagrams in one or more figures. These figures provide representative control strategies and / or logic that can be implemented using one or more processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and similar strategies. In this sense, the depicted steps and functions can be executed in the sequence shown, in parallel, or, in some cases, omitted. Although not always explicitly shown, experts will recognize that one or more of the depicted steps or functions can be executed repeatedly, depending on the specific processing strategy employed.Similarly, the processing sequence is not necessarily required to achieve the features and benefits described herein, but serves for illustration and description. The control logic can be implemented primarily in software executed by a microprocessor-based vehicle, propulsion system, and / or powertrain control unit, such as the Control Unit 50. Of course, the control logic can be implemented in software, hardware, or a combination of hardware and software in one or more control units, depending on the specific application. If implemented in software, the control logic can be provided in one or more computer-readable storage devices or media containing data representing code or instructions to be executed by a computer to control the vehicle or its subsystems.The computer-readable storage devices or media may comprise one or more of a number of known physical devices that use electrical, magnetic and / or optical storage to store executable instructions and associated calibration information, operating variables, and the like.

[0017] An accelerator pedal 52 is used by the vehicle's driver to provide a requested engine speed, power output, or driving command to propel the vehicle. The pedal 52 may include a pedal position sensor. Generally, pressing and releasing the pedal 52 causes the pedal sensor to generate an accelerator pedal position signal, which is interpreted by the control unit 50 as a request for increased or decreased power. Based on at least the pedal input, the control unit 50 commands torque from the drive system 14 and / or the M / G 18. The control unit 50 also controls the timing of gear changes within the gearbox 24, as well as the engagement or disengagement of the release clutch 26 and the torque converter bypass clutch 34. Like the release clutch 26, the bypass clutch 34 can be modulated over a range between the engaged and disengaged positions.This generates variable slip in the torque converter 22, in addition to the variable slip generated by the hydrodynamic coupling between the impeller and the turbine. Alternatively, the bypass clutch 34 can be operated in either the closed or open position without using a modulated mode, depending on the specific application.

[0018] To drive the vehicle with the drive system 14, the release clutch 26 is at least partially engaged to transmit at least some of the drive torque through the release clutch 26 to the M / G 18, and then from the M / G 18 through the torque converter 22 and gearbox 24. When the drive system 14 alone provides the necessary torque to propel the vehicle, this process can be referred to as "internal combustion engine mode", "engine-only mode", or "mechanical mode".

[0019] The M / G 18 can assist the drive system 14 by providing additional power to rotate the shaft 30. This operating mode can be referred to as "hybrid mode", "combination mode", or "electric auxiliary mode".

[0020] To operate the vehicle using the M / G 18 as the sole power source, the power flow remains the same, except that the disengagement clutch 26 isolates the drive system 14 from the rest of the drivetrain 12. Combustion in the drive system 14 may be deactivated or otherwise switched off during this time to conserve fuel. The traction battery 20 transfers stored electrical energy through the wiring 54 to the power electronics 56, which may include, for example, an inverter and a DC-DC converter. The power electronics 56 converts the DC voltage from battery 20 into AC voltage used by the M / G 18. The control unit 50 instructs the power electronics 56 to convert voltage from battery 20 into AC voltage supplied to the M / G 18 in order to provide positive (e.g., drive) or negative (e.g., regenerative) torque to the shaft 30.This operating mode can be referred to as "purely electric mode" or "electric car mode" or "electric motor mode".

[0021] In each operating mode, the M / G 18 can function as a motor and provide drive power for the drivetrain 12. Alternatively, the M / G 18 can function as a generator, converting kinetic energy from the drivetrain 12 into electrical energy, which is stored in battery 20. The M / G 18 can also function as a generator while the drive system 14, for example, provides drive power to the vehicle 10. Furthermore, the M / G 18 can function as a generator during regenerative braking phases, in which rotational energy from the rotating wheels 42 is transferred back into electrical energy through the gearbox 24 and converted into electrical energy for storage in battery 20.

[0022] One will be able to understand that this in Fig. The diagram shown in Figure 1 is purely illustrative and not intended to be restrictive. Other configurations are considered that utilize selective actuation of both a drive system and a motor for transmission through the gearbox. For example, the M / G 18 may be offset from the crankshaft 28, an additional motor could be provided to start the drive system 14, and / or the M / G 18 may be positioned between the torque converter 22 and the gearbox 24. Other configurations are considered without deviating from the scope of this disclosure.

[0023] Most conventional vehicles with automatic transmissions have a creep control feature that allows the driver to move the vehicle at low engine speeds simply by releasing the brake pedal without pressing the accelerator. Creep control uses the torque generated at engine idle speed to propel the vehicle. Most automatic transmissions have a torque converter. The torque converter's impeller transfers torque to the turbine (which is connected to the transmission input shaft) hydrodynamically. This hydrodynamic coupling only occurs when the impeller speed is above the turbine stall speed. The torque converter is configured so that the idle speed is above the stall speed. Therefore, in a conventional vehicle, the impeller and turbine are hydrodynamically coupled when the drive system is ON.The vehicle will be propelled without delay if the torque of the drive system exceeds the braking torque, which usually occurs before the brake pedal is fully released.

[0024] Drivers have become accustomed to creep control, so it would be advantageous to program electric and hybrid vehicles to mimic the creep control of conventional vehicles. Instead of using the drive system, hybrid vehicles can provide creep torque using the electric motor. In hybrid vehicles with a torque converter (such as Vehicle 10), the electric motor can be programmed to rotate at an idle speed (e.g., 800 RPM) to maintain hydrodynamic coupling with the torque converter when creep control is anticipated. Unlike conventional vehicles, where the impeller rotates at idle speed when the vehicle is stopped with the engine running, hybrid vehicles typically disengage the electric motor when stopped to conserve battery state of charge (SOC).Therefore, hydrodynamic coupling is not maintained when a hybrid vehicle is stopped. If creep torque is requested, the impeller must spin up to turbine stall speed before creep torque is provided to the driven wheels. Drivers expect the instantaneous drive that conventional vehicles offer when the brakes are at least partially released. To limit deceleration and provide a satisfying driving experience, hybrid vehicles should spin the impeller up to turbine stall speed as quickly as possible to limit deceleration. When the turbine is throttled, the torque converter's reaction forces are low, and much of the electric motor's torque is used to accelerate the impeller. Creating a control strategy that accelerates the impeller quickly and accurately to idle speed is difficult to implement.

[0025] Fig. Figure 2 shows diagrams of a fan / motor speed linked to a feedback control system for rotating the fan. The feedback control can use proportional-integral-derivative (PID) control to adjust the torque applied by the electric motor. In this strategy, the control unit calculates a target speed curve 60. Using feedback control, the electric motor increases or decreases the torque to reduce the difference between the target speed 60 and the measured speed 62. The speeds can be those of the fan or the electric motor. One problem with pure feedback control is that the speed can overshoot the target idle speed shown as 64. This results in jerky torque that the driver feels and is considered an unsatisfying driving experience. Another problem is that the measured speed 62 lags behind the target speed 60.In the illustrated example, the target speed diagram 60 reaches idle speed 50 milliseconds faster than the actual speed diagram 62. This time difference is noticeable to the driver and may be perceived as an unsatisfactory delay. One way to avoid this overshoot using feedback control is to limit the slope of the target speed 60 near idle speed. While this can reduce the overshoot, it increases the time the impeller takes to reach idle speed, which may not be desirable.

[0026] To solve these and other problems, the rotation of the impeller can be controlled by a control strategy that incorporates a torque algorithm with feed-forward and feedback components. Equation 1 is an example of an electric machine speed equation that includes both feed-forward and feedback components. τ=Jdω Conductancedt±P⋅e+I∫edt+D⋅e˙ where: J is the inertia of the impeller; ω is the angular velocity; e is the deviation between ω Leitwert and ω Messwert is; as well as P, I and D being constants of the PID controller.

[0027] Equation 1 can be used to control the torque relative to M / G 18 during impeller spin-up. Impeller spin-up is typically initiated in response to the vehicle being stopped, the impeller being below turbine stall speed (idle speed), and the driver requesting creep control. For example, impeller spin-up may be initiated when the braking torque requested by the driver approaches the wheel torque generated by the impeller while rotating at idle speed. The feed-forward component comprises one or more predetermined torques applied over a predetermined period. The predetermined period may be the time it takes for the impeller to spin up to the desired idle speed. The predetermined torques may be stored in one or more lookup tables held in the memory of control unit 50.Different feed-forward torques can be applied in different situations. For example, one feed-forward torque can be used when the impeller is turned to assist a shift from NEUTRAL to DRIVE, and another when the brake pedal is released with the transmission in DRIVE.

[0028] The feedback component adjusts the feed-forward component based on a deviation (e) between the guide speed and the measured speed of the impeller 35 or the M / G 18. The feedback loop can use PID controllers or PD / PI controllers. The feedback torque can be limited to plus or minus 40 newton meters (Nm) because most of the torque is provided by the feed-forward component. If the deviation requires a torque correction exceeding 40 Nm, mechanical failure may be present, and limiting the feedback could reduce potential damage because the feed-forward torque is only provided for a short time. (In contrast, feedback control does not have this capability without employing other checks.) The speeds can be the impeller speed or the M / G speed. In vehicle 10, the rotor 19 and the impeller 35 are fixed relative to each other.Since electric machines typically contain a speed sensor, unlike torque converters which do not, the following example controllers use M / G speeds in Equation 1, as no additional speed sensors are required.

[0029] Fig. Sections 3A to 3C show a series of diagrams illustrating a combined feed-forward and feedback control strategy. These diagrams are presented in conjunction with flowchart 100 in [reference missing]. Fig. 4 described. As experts will understand, the functions represented by the flowchart blocks can be executed by software and / or hardware. Depending on the specific processing strategy, e.g., event-driven, interrupt-driven, etc., the various functions may be executed in a different sequence or order than that shown in the figures. Similarly, one or more steps or functions may be performed repeatedly, even if this is not explicitly shown. In one embodiment, the depicted functions are implemented primarily by software, instructions, code, or control logic stored in a computer-readable storage medium and executed by one or more microprocessor-based computers or control units to control the operation of the vehicle. All depicted steps or functionsFunctions are not strictly necessary to provide various features and advantages according to the present disclosure. In this sense, some steps and functions can be omitted in some applications or implementations. The algorithm for controlling a motor in a HEV according to an embodiment of the present disclosure as in . Fig. Figure 4 includes steps or functions represented by control logic or software and executed by one or more microprocessor-based control units, such as control unit 50.

[0030] In process 102, the control unit 50 determines whether the driver requests creep control. It can determine whether creep control is requested in response to one or more of the following: the drive system is OFF, the transmission is in DRIVE, the electric motor speed is zero, the vehicle speed is zero, a brake pedal is released beyond a limit position (this limit can vary depending on vehicle weight and road gradient), and the accelerator pedal is not depressed. If creep control is requested, the control unit proceeds to process 103 and determines whether the M / G speed is below the turbine stall speed. If not, the control unit returns to the starting point. If so, the control unit enters impeller spin control and proceeds to process 104. In process 104, a target M / G speed diagram 66 is calculated.The speed diagram 66 can include one or more speed rates, such as a first rate 68, a second rate 70, and a third rate 72. Having more than one rate allows for greater control over the impeller's acceleration during cranking. The first target rate 68 can be used between a minimum M / G speed of zero and an M / G speed corresponding to the speed required to establish line pressure within the gearbox (e.g., 300 RPM). The first rate 68 can be the steepest rate for quickly generating line pressure in the gearbox. It can also be the steepest because it is furthest from the idle speed and therefore less likely to exceed the idle speed, which should be avoided. The second rate 70 can be the second steepest rate and is used between the line pressure speed and another M / G speed, which can vary depending on operating conditions.The third rate, 72, can be the flattest to avoid exceeding the idle speed. Of course, this example with three speed rates is not meant to be restrictive; more or fewer rates can be used.

[0031] In process 106, the control unit calculates a feed-forward torque 74 for each of the rotational speed rates. Each feed-forward torque is recommended for a predetermined time interval, corresponding to the time the M / G (and the impeller) are expected to take to reach the target rotational speed. In the illustrated embodiment, three feed-forward torques are calculated because three rates are used. A first feed-forward torque 76 is recommended during the first rate 68, a second feed-forward torque 78 is recommended during the second rate 70, and a third feed-forward torque 80 is recommended during the third rate 72. Accelerating the impeller from rest requires more torque than continuing to accelerate it. Therefore, the first feed-forward torque 76 is the highest torque, and the last feed-forward torque 80 is the lowest torque.In process 108, a torque command is generated and sent to the M / G 18.

[0032] In process 110, the M / G rotational speed can be determined by a speed sensor that measures a component associated with the M / G. In one embodiment, the M / G 18 includes a speed sensor that measures the angular velocity of the rotor 19. The speed sensor can be an encoder sensor. The speed sensor is configured to output a signal to the control unit indicating the rotational speed of the rotor 19. Since the impeller and the rotor are fixed, the rotational speed of the impeller can be deduced from the rotor rotational speed. The measured M / G rotational speed 73 is recorded as track 73 in Fig. 3A shown

[0033] In step 112, the control unit determines the relative weighting between the feedback torque and the feed-forward torque. This could be achieved by adjusting the gain values ​​of the PID control unit or by applying a scaling factor to the feedback torque. During the first rate, when the feed-forward torque is at its highest, low values ​​could be chosen for the feedback gain. As the impeller speed increases, for example, during the third rate and later, higher values ​​could be selected for the feedback gain (e.g., higher values ​​than during rate 1).

[0034] In step 114, the feedback torque is calculated based on speed deviation 82. The deviation 82 could be the difference between an M / G guide speed 66 and the measured M / G speed 73. The control unit dynamically inserts the speed deviation 82 into the feedback component of equation 1 and adjusts the speed command accordingly, either up or down, to reduce the speed deviation in step 116. The feedback torque is then calculated in Fig. 3C is shown as track 86. During process 118, the control unit provides the adapted torque command 84 to the M / G 18.

[0035] Fig.Figure 5 shows a control arrangement that, according to an algorithm with feed-forward and feedback components, issues a torque command to the M / G 18. In response to the creep control request and the fact that the impeller is below turbine stall speed, the control unit inputs an impeller spin control mode, in which the torque is provided to the M / G 18 according to Equation 1, for example. In this mode, an M / G (or impeller) guide speed is generated based on the mapping stored in the vehicle's memory. Based on the M / G (or impeller) guide speed, a feed-forward torque command 130 is generated using Equation 1, which is proportional to the rate of change of the speed request. The feed-forward torque can be weighted according to the impeller's inertia and then sent to the M / G 18.The feed-forward torque is adjusted by a deviation (e) based on a difference between the M / G guide speed and the measured M / G speed. A speed sensor 132 of the M / G 18 can send a speed signal to the control unit 50 to determine the deviation between the guide speed and the measured speed. The deviation is fed into the feedback components 134, and a feedback torque is calculated. The feedback torque can be weighted. The feed-forward torque is then adjusted by the feedback torque, and a torque command 138 is issued to the M / G 18. This sequence can be repeated at a predetermined frequency until the control unit exits the impeller rotation control.

[0036] The processes, procedures, or algorithms disclosed herein may be implemented or provided to a processing device, control unit, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, procedures, or algorithms may be stored as data and instructions executable by a control unit or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media such as ROM devices, and information modifiably stored on writable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, procedures, or algorithms may also be implemented in a software executable object.Alternatively, the processes, procedures or algorithms can be implemented wholly or partially using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, control units or other hardware components or devices, or a combination of hardware, software and firmware components.

[0037] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the patent specification are descriptive rather than limiting, and it is understood that various modifications can be made without departing from the spirit and scope of the disclosure. As previously described, features of different embodiments can be combined to form further embodiments of the invention that may not have been expressly described or illustrated.While it is possible that various embodiments have been described as advantageous or preferable to other embodiments or the prior art with respect to one or more desired properties, those skilled in the art will recognize that one or more features or characteristics may be reduced to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to: durability, service life, life-cycle costs, marketability, appearance, packaging, size, usability, weight, manufacturability, ease of assembly, etc.Insofar as embodiments are described as less desirable with respect to one or more characteristics than other embodiments or implementations according to the prior art, these embodiments are not outside the scope of the disclosure and may be desirable in certain applications.

Claims

[1] vehicle, comprising the following: a drive train with an electric machine that is driven by a turbine wheel of a torque converter; and a control unit configured to instruct the electric machine to provide torque to the impeller in response to a vehicle speed of zero and a brake pedal released beyond a limit position, wherein the torque is a predetermined feed-forward torque adapted by a feedback torque based on a difference between measured and calculated rotational speeds of the electric machine, the feed-forward torque being based on the inertia of the impeller. [2] Vehicle according to claim 1, wherein the command to provide the torque is further issued in response to a drive system of the powertrain being OFF. [3] Vehicle according to claim 1, wherein the command to provide the torque is further issued in response to a transmission of the drive train being in DRIVE. [4] vehicle, comprising the following: a drive system; a gearbox, including a torque converter with a paddle wheel; an electric machine designed to provide drive torque to the impeller and selectively coupled to the drive system via a clutch; and at least one vehicle control unit configured to instruct the electric machine to provide torque to the impeller in response to the drive system being set to OFF, the transmission being set to DRIVE, a vehicle speed of zero and a brake pedal released beyond a limit position, wherein the torque is a predetermined feed-forward torque adapted by a feedback torque based on a difference between measured and calculated rotational speeds, wherein the feed-forward torque is based on the inertia of the impeller. [5] Vehicle according to claim 4, wherein the measured and calculated rotational speeds are the measured and calculated rotational speeds of the electric machine. [6] Vehicle according to claim 4, wherein the feedback torque is limited to a predetermined maximum torque. [7] Vehicle according to claim 4, wherein the control unit is further configured to apply the feed-forward torque for a predetermined period of time. [8] Vehicle according to claim 1 or 4, wherein the feed-forward torque comprises a first feed-forward torque which is directed for a first time period and a second feed-forward torque which is directed for a second time period which lies after the first time period. [9] Vehicle according to claim 8, wherein the first feed-forward torque is greater than the second feed-forward torque. [10] Vehicle according to claim 4, wherein a rotor of the electric machine and the impeller are attached to each other. [11] Method for restarting a torque converter impeller connected to an electric machine, the method comprising: In response to a vehicle speed of zero and a brake pedal released beyond a limit position, the electric machine is instructed to provide a torque to the impeller, wherein the torque is a predetermined feed-forward torque adjusted proportionally to a difference between measured and calculated electric machine speeds, the feed-forward torque being based on the inertia of the impeller. [12] Method according to claim 11, wherein the proportional adjustment of the feed-forward torque is limited to a predetermined maximum torque. [13] Method according to claim 11, further comprising issuing a creep command in response to an electrical machine speed of zero and a brake pedal being released beyond a limit position.

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