Correction of engine torque estimate

Abstract

The present disclosure relates to correction of engine torque estimation. An engine torque correction factor table is used to compensate for noise factors. In a hybrid vehicle, a motor is used to measure engine torque during a period of time when the transmission input shaft torque is constant. By comparing the measured input torque to the requested engine torque, a controller may update the correction factor table to compensate for changes in the noise factors. A service procedure may be implemented that systematically provides the controller with an opportunity to update multiple values ​​in the table.

Description

Technical Field

[0001] The present disclosure relates to the field of control of hybrid electric vehicles. More specifically, the present disclosure relates to a procedure for adjusting an engine torque correction factor. Background Art

[0002] Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse motion. However, some types of engines can only operate efficiently over a narrow speed range. Therefore, a transmission that can efficiently transfer power at a variety of gear ratios is often used. When the vehicle is at low speeds, the transmission is often operated at a high gear ratio, so that the engine torque is multiplied to improve acceleration. At high vehicle speeds, operating the transmission at a low gear ratio allows engine speeds associated with quiet, energy-efficient cruising.

[0003] To reduce fuel consumption, some vehicles include hybrid powertrains that utilize energy storage devices to supplement the power produced by the internal combustion engine. These powertrains allow the vehicle to operate with the engine off for a period of time and operate at the engine's more efficient torque level for the remainder of the time. Hybrid powertrains are also able to capture and subsequently use energy that would otherwise be consumed by the braking system. Summary of the invention

[0004] A vehicle includes a motor, an internal combustion engine, and a controller. The motor is fixedly connected to a transmission input shaft. The internal combustion engine is selectively connected to the transmission input shaft through a clutch. The controller is configured to respond to a driver torque demand at an input shaft speed by commanding the engine to produce a commanded engine torque, wherein the commanded engine torque is based on a stored torque correction factor. In an optional embodiment, the commanded motor torque may be adjusted based on the correction factor to ensure the delivery of the desired total torque. With the clutch disengaged, when the motor is operated in a speed control mode at the input shaft speed, the controller measures a first measured motor torque. Then, with the clutch engaged, when the motor is operated in a speed control mode at the input shaft speed, the controller commands the engine to produce a first commanded engine torque and measures a second measured motor torque. The controller updates the torque correction factor as the difference between the first measured motor torque and the sum of the commanded engine torque and the second measured motor torque. The torque correction factor may be stored in a table as a function of the engine speed and the engine torque, and updated by replacing at least one value in the table. The motor torque may be measured during an operating condition where the transmission input shaft torque is constant. These operating conditions may occur during normal driving (such as idling, creeping, in park or neutral) or when driving under cruise control. The operator-selected service program may systematically provide the operating conditions.

[0005] According to the present invention, a vehicle is provided, which includes: a motor fixedly connected to a transmission input shaft; an internal combustion engine selectively connected to the transmission input shaft through a clutch; a controller configured to: in response to a driver torque demand at an input shaft speed, command the internal combustion engine to generate a commanded engine torque, wherein the commanded engine torque is based on a stored torque correction factor; when the clutch is disengaged, when the motor is operated in a speed control mode at the input shaft speed, measure a first measured motor torque; when the clutch is engaged, when the motor is operated in a speed control mode at the input shaft speed, command the internal combustion engine to generate a first commanded engine torque and measure a second measured motor torque; and update the torque correction factor as a difference between the first measured motor torque and the sum of the commanded engine torque and the second measured motor torque.

[0006] According to an embodiment of the invention, said transmission input shaft torque is set by a cruise control function in said operating condition.

[0007] According to an embodiment of the invention, the transmission input shaft is not driveably connected to vehicle wheels in said operating condition.

[0008] A vehicle includes a motor, an internal combustion engine, and a controller. The motor is fixedly connected to a transmission input shaft. The internal combustion engine is selectively connected to the transmission input shaft through a clutch. When the motor is operated in a speed control mode with a constant input shaft torque, the controller is configured to: measure a first measured motor torque with the clutch disengaged; engage the clutch; command the engine to produce a commanded engine torque, and measure a second measured motor torque. The controller may also be configured to: store an engine torque correction factor, the engine torque correction factor being equal to the difference between the first measured motor torque and the sum of the second measured motor torque and the commanded engine torque. The controller may also be configured to: respond to a requested engine torque by commanding the engine to produce a commanded engine torque, wherein the requested engine torque differs from the commanded engine torque by a torque correction factor. The controller may also be configured to: operate in a service mode, in which the torque correction factor is stored for a set of transmission input shaft speeds.

[0009] According to the present invention, a method is provided, the method comprising: in response to a driver's torque demand at an input shaft speed, commanding an engine to generate a first commanded engine torque based on a stored correction factor; generating a motor torque when commanding the engine to generate the first commanded engine torque when the motor is operated in a speed control mode at the input shaft speed with a transmission input shaft torque being constant; in response to a driver's torque demand at the input shaft speed, commanding the engine to generate a second commanded engine torque different from the first commanded engine torque based on a stored correction factor, wherein the correction factor is updated based on the commanded engine torque, the motor torque and the constant input shaft torque.

[0010] According to one embodiment of the present invention, the constant input shaft torque is measured by operating the motor in a speed control mode at an input shaft speed at a constant transmission input shaft torque when the engine is decoupled from the transmission input shaft by a clutch.

[0011] According to one embodiment of the invention, the updated correction factor is equal to the difference between the constant input shaft torque and the sum of the commanded engine torque and the motor torque.

[0012] According to one embodiment of the present invention, a constant input shaft torque is generated by placing the transmission in a neutral state.

[0013] A vehicle includes a motor, an internal combustion engine, and a controller. The motor is fixedly connected to a transmission input shaft. The internal combustion engine is selectively connected to the transmission input shaft through a clutch. In a service mode selected by an operator, the controller is configured to: command the motor to rotate at a first speed; measure a first measured motor torque when the clutch is disengaged; command the engine to produce a first commanded engine torque when the clutch is engaged, and measure a second measured motor torque. The controller may also be configured to: store a first engine torque correction factor, the first engine torque correction factor being equal to the difference between the first measured motor torque and the sum of the second measured motor torque and the first commanded engine torque. The controller may also be configured to: in the service mode, when the clutch is engaged, command the engine to produce a second commanded engine torque, measure a third measured motor torque, and store a second engine torque correction factor, the second engine torque correction factor being equal to the difference between the first measured motor torque and the sum of the third measured motor torque and the second commanded engine torque.

[0014] According to the present invention, a vehicle is provided, which includes: a motor fixedly connected to a transmission shaft; an internal combustion engine selectively connected to the transmission shaft through a clutch; and a controller configured to: in a service mode selected by an operator, perform the following operations: command the motor to rotate at a first speed; measure a first measured motor torque when the clutch is disengaged; and command the internal combustion engine to generate a first commanded engine torque and measure a second measured motor torque when the clutch is engaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram showing a powertrain of a hybrid vehicle.

[0016] Figure 2 Correction factor tables are used to control Figure 1 Flow chart of the method for a powertrain system with an internal combustion engine and a traction motor.

[0017] Figure 3 is a flow chart of a first method for updating the correction factor table.

[0018] Figure 4 is a flow chart of a second method for updating the correction factor table. DETAILED DESCRIPTION

[0019] As required, specific embodiments of the present invention are disclosed herein. However, it will be understood that the disclosed embodiments are merely exemplary of the present invention, which may take various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present invention in various forms.

[0020] Figure 1 A hybrid vehicle powertrain is schematically shown. A traction motor 10 generates torque using electrical energy stored by a battery 12. In some operating modes, the traction motor 10 can be operated to generate electrical energy, which is then stored in the battery 12 for later use. For example, the traction motor can be a synchronous AC (alternating current) motor combined with an inverter. The rotor of the traction motor 10 is fixed to a transmission input shaft 14. Power from the transmission input shaft 14 is delivered to the vehicle wheels via a torque converter 16, a gearbox 18, and a differential 20.

[0021] The torque converter 16 includes a pump wheel fixedly connected to the transmission input shaft 14 and a turbine fixedly connected to the input of the gearbox 18. Whenever the pump wheel rotates faster than the turbine, the torque converter 16 transfers power from the pump wheel to the turbine. The torque converter 16 may also include a stator that multiplies the torque so that the torque on the turbine is greater than the torque on the pump wheel. The torque converter 16 may also include a locking clutch that selectively connects the pump wheel to the turbine to achieve more efficient power transfer when the slip associated with the fluid dynamic power transmission between the pump wheel and the turbine is not required.

[0022] The gearbox 18 includes a number of clutches and brakes that establish various power flow paths from the gearbox input shaft to the transmission output shaft. These power flow paths have different gear ratios. The transmission switches from one power flow path to another power flow path by disengaging one or more clutches or brakes and engaging other clutches or brakes. A neutral mode is established when there is no power flow path between the gearbox input and the transmission output. The gearbox 18 may also include a parking pawl that can be engaged when the vehicle is idle to keep the transmission output stationary.

[0023] The transmission output shaft is connected to a differential 20 which divides power between left and right drive wheels 22, 24. The differential allows for slight speed differences between the wheels, such as when the vehicle is turning.

[0024] The internal combustion engine 26 is selectively connected to the transmission input shaft 14 through the clutch 28. It should be noted that the transmission input shaft 14 extends through the traction motor 10. When the clutch 28 is engaged, the engine 26 and the traction motor 10 rotate at the same speed, and the torque on the transmission input shaft 14 is equal to the sum of the torque generated by the engine 26 and the torque generated by the traction motor 10. In some operating modes, the engine 26 can provide all the power for propulsion by setting the torque of the traction motor to zero. In other operating modes, the traction motor can draw power from the battery 12 to assist in propelling the vehicle. In other operating modes, the engine can generate more power than is required for propulsion, at which time the motor diverts some power to charge the battery 12. When the clutch 28 is disengaged, all propulsion is provided by the traction motor 10.

[0025] The powertrain system is controlled by a controller 30. The controller 30 can be a single microprocessor or multiple communicating microprocessors. The controller 30 receives commands from the driver via the accelerator pedal position, the brake pedal position, the position of the shift selector (PRNDL), etc. The controller also uses signals from various sensors. The controller controls the engagement and disengagement of the clutch 28, the torque converter lockup clutch, and the clutches and brakes within the gearbox 18. The controller also sends commands to the engine 26 and the traction motor 10 indicating how much torque they should produce.

[0026] In some operating modes, the controller 30 may operate the traction motor 10 in a speed control mode, in which the controller commands a specific speed. Some motors may perform this speed control directly, while other motors may use feedback signals to adjust the torque command to perform the speed control mode. In such feedback systems (such as proportional, derivative, integral (PDI) controllers), the torque is adjusted as needed to maintain the commanded speed. In the speed control mode, the controller is able to measure the motor torque. When the speed control mode is performed via feedback control, the torque is measured by recording the average torque command required to maintain the commanded speed. When the speed control mode is performed directly, the controller is able to calculate the torque based on measurements of current, voltage, and phase.

[0027] However, the torque produced by the engine is not always equal to the torque commanded by the controller. Various noise factors can cause the torque produced to be less or more than the torque commanded. These noise factors include changes and degradation of different parts over time. To a significantly lesser extent, the motor torque is not always equal to the torque commanded by the controller. These torque delivery errors are most likely to be noticed by the vehicle occupants when the controller changes the relative proportions of the engine torque and the motor torque. Unless the driver changes the position of the accelerator, the driver expects the total transmission input torque to remain constant. However, due to inaccuracies in the engine's torque delivery, the total transmission input torque can change.

[0028] like Figure 2As shown in the process of , in order to reduce the engine torque error, the controller can use a torque correction factor table. At 32, the controller calculates the target output torque based on the accelerator pedal position and the vehicle speed. At 34, the controller calculates the total target transmission input torque based on the target output torque and the torque amplification of the gearbox and the torque converter. At 36, the controller divides the target total transmission input torque into a target motor torque and a target engine torque. This can be based on several factors, including engine efficiency characteristics, current battery charge state, etc. At 38, the controller looks up the engine torque correction factor as a function of the target engine torque and the current engine speed. The correction factor can be stored in a table. Interpolation may be required for engine speeds and target engine torques that fall between the tabulated values. At 40, the requested engine torque is calculated by subtracting the correction factor from the target engine torque. In an optional embodiment, the correction factor can be used to adjust the commanded motor torque to ensure that the desired total torque is delivered. At 42, the controller sends a torque request equal to the requested engine torque to the engine. The engine controller can convert the torque request into throttle position, spark timing, injector settings, etc., and send these requests to the appropriate actuators. If the engine controller is integrated into the controller 30, the controller 30 will perform these conversions and the individual actuator commands should be treated as sending torque requests. At 44, the controller sends a torque request to the traction motor 10. The motor controller then converts the torque request into specific inverter settings.

[0029] As long as the correction factors in the lookup table accurately indicate the difference between the requested engine torque level and the torque delivered by the engine, the engine will deliver the target engine torque. The correction factor lookup table may be initially populated based on measurements performed at the factory on a new vehicle. It is advantageous to update the tabulated correction factors to ensure that they continue to accurately reflect engine behavior as noise factors change over time. The correction factors are periodically updated during normal vehicle operation to correct for changes due to gradual wear and seasonal changes.

[0030] Figure 3 The flowchart of FIG. 5 shows a method for updating the correction factor in a timely manner. At 50, the controller determines whether the current operating condition is a steady-state condition. The steady-state condition is characterized by a constant transmission input shaft speed and a constant transmission input shaft torque. Some examples of steady-state conditions include:

[0031] ●Park or neutral (transmission input shaft torque can be ignored),

[0032] ● Idle speed when the vehicle is stationary (the transmission input shaft torque is based on the torque converter characteristics),

[0033] ●Crawling on a constant slope (the transmission input shaft torque is based on the torque converter characteristics and the slope),

[0034] ●Cruise control on constant grade (transmission input shaft torque is based on grade, windage and rolling resistance),

[0035] ●Running with a dynamometer, where the dynamometer controls the speed.

[0036] At 52, the controller commands the release of the clutch 28 and commands the engine to shut down. At 54, the controller commands the traction motor 10 to operate in a speed control mode. The speed is commanded depending on which steady-state condition is detected at 50. For example, for parking, neutral or creeping conditions, the motor may be commanded to a speed close to the engine idle speed. In cruise control, the motor is commanded to a speed that produces the desired vehicle speed. At 56, the controller records the torque produced by the traction motor 10. This torque is considered to be the total transmission input torque for this steady-state operating condition. At 58, the controller commands the engine to start and commands the clutch to engage. If the traction motor 10 was temporarily operated in some other mode during the engine starting process, the traction motor 10 is returned to the speed control mode at the same commanded speed.

[0037] As processing continues, the engine is commanded to produce various levels of torque. These torque levels can be predetermined levels recorded in the correction factor table. At 60, the requested engine torque is set to the first of these levels. At 62, the torque request is sent to the engine. At 64, the controller checks to see if the steady-state condition is still continuing. If the steady-state condition is not continuing, the program exits. Since the motor 10 is operating in the speed control mode, the motor 10 adjusts its output torque so that the sum of the engine torque and the motor torque is the same as the total torque recorded at 56. At 66, the measured engine torque is calculated by subtracting the measured motor torque from the previously recorded total torque. At 68, a new correction factor is calculated by subtracting the requested engine torque from the measured engine torque. At 70, the correction factor table is updated.

[0038] Several methods are known for adaptively updating a lookup table. These methods include both random adjustment methods and periodic adjustment methods. The random adjustment method updates the values ​​in the lookup table in response to individual observations. One such method described in European patent application EP 1712767A1 is incorporated herein by reference. When the observed result is different from the value estimated by the lookup table, the value stored for the nearby value of the independent variable is modified so that the new dependent variable value for the observed independent variable is closer to the observed result. For stability, the adjustment method may not allow large changes in a single update. In the periodic adjustment method, multiple observations are stored and then a curve fitting process is performed to calculate new values ​​for the model parameters. As with the random adjustment method, there may be restrictions on the adjustment rate and there may be boundaries beyond which adjustment is not allowed.

[0039] At 72, the controller checks whether more levels of engine torque should be checked. If no more levels of engine torque need to be checked, the process ends and the traction motor and engine resume normal operation. If more levels exist, at 74, the requested engine torque is set to the next level and the process repeats starting at 62.

[0040] Even if there are unknown noise factors affecting motor torque delivery, it is advantageous to consider the measured motor torque as the actual torque for the operating condition at 56. This ensures that the total torque will be constant any time the controller switches from motor-only operation to motor and engine operation.

[0041] Updating the correction factor table in a timely manner when vehicle operating conditions permit may not result in frequent updates of the higher speed entries in the table. Therefore, it may be advantageous to periodically perform a system routine for updating the table. For example, the above system routine may be performed after any service procedure that may change the noise factors that affect the engine torque level.

[0042] exist Figure 4. The system update program is shown in . The program is actively selected by the vehicle operator (such as a service technician). The vehicle display can be used to guide the operator through the program. Optionally, the operator can be instructed via voice commands from the audio system. At 80, the controller checks whether the program has been selected. For example, the selection can be made via a menu option in the driver interface. Optionally, the selection can be made through a series of manipulations of the brake pedal, accelerator pedal, gear shifter, etc. that would not normally occur during normal driving. If the program is selected, then at 82, the controller checks whether a set of preconditions are met. These preconditions may include whether the battery state of charge is sufficient for the motor during part of the program, while not being too high for the battery to absorb excess power generated during other parts of the program. In addition, vehicle settings that may change the torque transmitted by the engine to the transmission must be avoided. Thus, for example, if the air conditioning is turned on, the driver is instructed to turn off the air conditioning at 84.

[0043] Once all preconditions are met, the operator is instructed to place the vehicle in park at 86 if the vehicle is not already in park. Alternatively, the procedure may be performed in neutral. At 88, the controller provides additional general instructions to the operator to prepare for the procedure. At 90, the controller determines the engine speed to be updated. If there are multiple speeds to be updated, the controller selects the first speed. At 92, the controller instructs the operator to depress the accelerator pedal to increase the impeller speed. This type of operator interaction is required to ensure the operator is present during the procedure. At 94, the controller checks if the impeller speed matches the selected regulated speed within a certain tolerance and continues to instruct the operator until the speeds match. At 96, the controller executes Figure 4 The process of causing the engine torque commanded by the engine to cycle through multiple levels and updating the correction factor table for these levels. At 98, the controller determines whether the correction factor table should be updated at additional speed levels. If the controller determines that the correction factor table should be updated at additional speed levels, control passes to 90 to update the table at these levels. Otherwise, the routine ends and normal operation is resumed.

[0044] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present invention. More specifically, the words used in the specification are descriptive rather than restrictive terms, and it should be understood that various changes may be made without departing from the spirit and scope of the present invention. In addition, the features of the embodiments of each implementation may be combined to form further embodiments of the present invention.

Claims

1. A vehicle comprising: a motor fixedly connected to a transmission input shaft; an internal combustion engine selectively connected to a transmission input shaft via a clutch; The controller is configured as: commanding an internal combustion engine to produce a commanded engine torque in response to an operator torque demand at an input shaft speed, wherein the commanded engine torque is based on a stored torque correction factor; measuring a first measured motor torque when operating the motor in a speed control mode at an input shaft speed with the clutch disengaged; commanding the internal combustion engine to produce a first commanded engine torque while operating the motor in a speed control mode at the input shaft speed with the clutch engaged, and measuring a second measured motor torque; The torque correction factor is updated as a difference between the first measured motor torque and the sum of the first commanded engine torque and the second measured motor torque.

2. The vehicle according to claim 1, wherein: The torque correction factor is stored in a table as a function of engine speed and engine torque, wherein updating the torque correction factor includes replacing at least one value in the table.

3. The vehicle according to claim 1, wherein: Operating the motor in a speed control mode includes commanding the motor to produce a commanded motor torque and adjusting the commanded motor torque based on a measured speed to maintain an input shaft speed, wherein measuring the motor torque includes recording the commanded motor torque that stabilizes the measured speed at the input shaft speed.

4. The vehicle according to claim 1, wherein: Measuring the first measured motor torque and the second measured motor torque occurs during operating conditions where the transmission input shaft torque is constant.

5. The vehicle of claim 4 further comprising a torque converter having a pump impeller fixed to the transmission input shaft and a turbine drivingly connected to vehicle wheels under said operating condition.

6. The vehicle according to claim 5, wherein: The vehicle wheels are stationary in the operating condition.

7. The vehicle according to claim 4, wherein: The operating conditions are established as part of an operator selected service mode.

8. A vehicle comprising: a motor fixedly connected to a transmission input shaft; an internal combustion engine selectively connected to a transmission input shaft via a clutch; The controller is configured to, when the transmission input shaft torque is constant and the motor is operated in a speed control mode, perform the following operations: measuring a first measured motor torque with the clutch disengaged; Engage the clutch; commanding an internal combustion engine to produce a commanded engine torque, and measuring a second measured motor torque; An engine torque correction factor is stored that is equal to a difference between the first measured motor torque and a sum of the second measured motor torque and the commanded engine torque.

9. The vehicle according to claim 8, wherein: The controller is further configured to respond to the requested engine torque by commanding the internal combustion engine to produce a commanded engine torque, wherein the requested engine torque differs from the commanded engine torque by a torque correction factor.

10. The vehicle according to claim 9, wherein: The controller is further configured to operate in a service mode in which a torque correction factor is stored for a set of transmission input shaft speeds.

11. A vehicle comprising: a motor fixedly connected to the transmission shaft; an internal combustion engine selectively connected to a transmission shaft via a clutch; The controller is configured to: in a service mode selected by an operator, perform the following operations: commanding the motor to rotate at a first speed; measuring a first measured motor torque with the clutch disengaged; commanding the internal combustion engine to produce a first commanded engine torque with the clutch engaged, and measuring a second measured motor torque; A first engine torque correction factor is stored that is equal to a difference between the first measured motor torque and a sum of the second measured motor torque and the first commanded engine torque.

12. The vehicle according to claim 11, wherein: The controller is further configured to, in the service mode, command the internal combustion engine to produce a second commanded engine torque with the clutch engaged, measure a third measured motor torque, and store a second engine torque correction factor, the second engine torque correction factor being equal to a difference between the first measured motor torque and the sum of the third measured motor torque and the second commanded engine torque.

13. The vehicle according to claim 11, wherein: The controller is further configured to: in the service mode, perform the following operations: commanding the motor to rotate at a second speed; measuring a fourth measured motor torque with the clutch disengaged; commanding the internal combustion engine to produce a third commanded engine torque with the clutch engaged, and measuring a fifth measured motor torque; A third engine torque correction factor is stored that is equal to a difference between the fourth measured motor torque and a sum of the fifth measured motor torque and the third commanded engine torque.

14. A method for modifying engine torque, comprising: In response to an operator torque request at an input shaft speed, commanding an engine to produce a first commanded engine torque based on a stored correction factor; generating a motor torque when the engine is commanded to generate a first commanded engine torque when the motor is operated in a speed control mode at an input shaft speed under a condition where the transmission input shaft torque is constant; In response to an operator torque demand at an input shaft speed, commanding the engine to produce a second commanded engine torque different from the first commanded engine torque based on a stored correction factor, Therein, the correction factor is updated based on the commanded engine torque, the motor torque, and the constant input shaft torque.

15. The method according to claim 14, wherein: The constant input shaft torque is measured by operating the motor in a speed control mode at an input shaft speed at a constant transmission input shaft torque when the engine is decoupled from the transmission input shaft by the clutch.

16. The method according to claim 14, wherein: The updated correction factor is equal to the difference between the constant input shaft torque and the sum of the commanded engine torque and the motor torque.

17. The method according to claim 14, wherein: Constant input shaft torque is produced by placing the transmission in neutral.

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