System and method for determining engine torque for controlling a powertrain

• US 6,434,466 B1
• Filed: 05/06/1999
• Issued: 08/13/2002
• Est. Priority Date: 05/06/1999
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Clark, Timothy Joseph, Pallett, Tobias John, Robichaux, Jerry Dean
• Primary Examiner(s): Louis-Jacques, Jacques H.
• Assistant Examiner(s): Broadhead, Brian J
• Application Number:
  US09/306,307
• Time in Patent Office: 1,195 Days
• Field of Search: 701/53, 701/54, 701/60, 701/61, 477/54, 477/107, 477/109, 477/110, 477/111
• US Class Current: 701/54
• CPC Class Codes: B60W 10/04 including control of propulsion units
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2510/107 Temperature
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2710/105 Output torque
• CPC Class Codes: B60W 30/18 Propelling the vehicle
• CPC Class Codes: B60W 30/1819 Propulsion control with control means using analogue circuits, relays or mechanical links
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power
• CPC Class Codes: F02D 2200/1006 Engine torque losses, e.g. friction or pumping losses or losses caused by external loads of accessories
• CPC Class Codes: F02D 2200/501 Vehicle speed
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2400/12 Engine control specially adapted for a transmission comprising a torque converter or for continuously variable transmissions
• CPC Class Codes: F02D 41/0225 in relation with the gear ratio or shift lever position
• CPC Class Codes: F16H 2059/385 Turbine speed

Abstract

A system and method for controlling a powertrain including an automatic transmission include determining a desired wheel torque, determining engine speed, determining turbine speed, determining a selected gear and associated selected gear ratio, determining a transmission spin loss based on a first function of the turbine speed and the selected gear, determining a transmission torque proportional loss based on a second function of the turbine speed and the selected gear, determining a desired engine torque based on the transmission spin loss, the transmission torque proportional loss, and the selected gear ratio, and controlling the powertrain using the desired engine torque such that actual wheel torque approaches the desired wheel torque. A transmission pump loss may also be determined based on line pressure and engine speed. An alternative strategy determines engine torque using a power-based calculation if the vehicle speed is above a predetermined threshold, and a gear ratio based calculation if the vehicle speed does not exceed the predetermined threshold. Strategies for determination of the desired or requested engine torque during a gear shift or ratio change include a first strategy which determines an engine torque corresponding to the current gear ratio and the target gear ratio with the desired engine torque being interpolated between the two values. Turbine speed may be determined by an appropriate sensor or estimated. Alternatively, torque converter slip may be utilized with the slip value held constant for a predetermined time during the ratio change.

Claims

1. A method for controlling a powertrain including an internal combustion engine and an automatic transmission having a plurality of selectable gears with associated gear ratios, the automatic transmission being coupled to the internal combustion engine via a torque converter having a turbine, the method comprising:

determining a desired wheel torque;

determining engine speed;

determining turbine speed;

determining a selected gear and associated selected gear ratio;

determining a transmission spin loss based on a first function of the turbine speed and the selected gear;

determining a transmission torque proportional loss based on turbine torque and a second function of the turbine speed and the selected gear;

determining a desired engine torque based on the transmission spin loss, the transmission torque proportional loss, and the selected gear ratio; and

controlling the powertrain using the desired engine torque such that actual wheel torque approaches the desired wheel torque.

2. The method of claim 1 further comprising:

determining a transmission pump loss based on the engine speed and a requested transmission hydraulic line pressure; and

wherein the step of determining a desired engine torque includes determining the desired engine torque based at least in part on the transmission pump loss.

3. The method of claim 1 wherein the step of determining a desired wheel torque comprises:

determining a desired powertrain output based at least in part on position of an accelerator pedal; and

converting the desired powertrain output to the desired wheel torque.

4. The method of claim 3 wherein the step of determining a desired powertrain output comprises determining a desired tractive effort.

5. The method of claim 3 wherein the step of determining a desired powertrain output comprises determining a desired wheel power.

6. The method of claim 1 wherein the step of determining turbine speed comprises estimating turbine speed based on engine speed and an estimate of torque converter slip.

7. The method of claim 1 further comprising:

determining a torque converter multiplication based on the turbine speed and the engine speed; and

wherein the step of determining a desired engine torque includes determining a desired engine torque based at least in part on the converter multiplication.

8. The method of claim 7 wherein the step of determining a torque converter multiplication comprises:

determining a friction term based on a torque converter clutch solenoid duty cycle, a proportionality constant, engine speed, and turbine speed;

determining a torque converter clutch capacity term based on the torque converter clutch solenoid duty cycle, engine speed, turbine speed, a time constant for the transmission hydraulic system, and a time delay between a converter clutch command and actuation of the converter clutch; and

adjusting the torque converter multiplication based on the friction term and the capacity term.

9. The method of claim 1 wherein the step of determining a desired engine torque further comprises:

determining a scaling factor based on the selected gear; and

multiplying the desired engine torque by the scaling factor prior to controlling the powertrain output based on-the desired engine torque.

10. The method of claim 1 wherein a ratio change from the selected gear to a target gear having an associated target gear ratio has been commanded and wherein the step of determining the desired engine torque comprises:

determining a first engine torque based on the selected gear, the selected gear ratio, the torque proportional loss, and the transmission spin loss;

determining a second torque proportional loss based on the target gear and a second turbine speed wherein the second turbine speed is based on the target gear ratio and output shaft speed;

determining a second transmission spin loss based on the target gear and the second turbine speed;

determining a second engine torque based on the second torque proportional loss, the second spin loss and the target gear ratio; and

determining the desired engine torque based on the first and second engine torques.

11. The method of claim 10 wherein the step of determining the desired engine torque comprises interpolating between the first and second engine torques.

12. The method of claim 1 wherein a ratio change from the selected gear to a target gear having an associated target gear ratio has been commanded, the method further comprising:

estimating a torque converter slip; and

storing the torque converter slip when the gear ratio has been commanded;

wherein the step of determining the desired engine torque includes determining the desired engine torque based on the stored torque converter slip for a predetermined time after the ratio change has been commanded.

13. The method of claim 1 wherein a ratio change from the selected gear to a target gear having an associated target gear ratio has been commanded, the method further comprising:

determining a torque ratio based on engine speed and engine inertia; and

adjusting spark based on the torque ratio for a predetermined time after the ratio change has been commanded to reduce actual engine torque during the ratio change.

14. A method for controlling a powertrain including an internal combustion engine and an automatic transmission having a plurality of selectable gears with associated gear ratios, the method comprising:

determining a desired wheel torque;

determining engine speed;

determining turbine speed;

determining a selected gear and associated selected gear ratio;

determining current vehicle speed;

determining desired engine torque based on wheel speed, the desired wheel torque, the engine speed, and the turbine speed when vehicle speed exceeds a corresponding threshold; and

determining the desired engine torque based on the desired wheel torque, the selected gear ratio, the engine speed, and the turbine speed when the vehicle speed does not exceed the corresponding threshold.

15. The method of claim 14 wherein the step of determining turbine speed comprises estimating turbine speed based on engine speed and an estimate of torque converter slip.

16. The method of claim 15 further comprising:

determining a value for torque converter slip upon initiation of a ratio change; and

maintaining the value for a predetermined time during the ratio change.

17. The method of claim 14 wherein a ratio change from the selected gear to a target gear having an associated target gear ratio has been commanded, the method further comprising:

determining a torque ratio based on engine speed and engine inertia; and

adjusting spark based on the torque ratio for a predetermined time after the ratio change has been commanded to reduce actual engine torque during the ratio change.

18. A computer readable storage medium having stored data representing instructions executable by a computer to control a powertrain having an internal combustion engine and an automatic transmission, the computer readable storage medium comprising:

instructions for determining a desired wheel torque;

instructions for determining engine speed;

instructions for determining turbine speed;

instructions for determining a selected gear and associated selected gear ratio;

instructions for determining a transmission spin loss based on a first function of the turbine speed and the selected gear;

instructions for determining a transmission torque proportional loss based on turbine torque and a second function of the turbine speed and the selected gear;

instructions for determining a desired engine torque based on the transmission spin loss, the transmission torque proportional loss, and the selected gear ratio; and

instructions for controlling the powertrain using the desired engine torque such that actual wheel torque approaches the desired wheel torque.

19. The computer readable storage medium of claim 18 wherein the instructions for determining turbine speed include instructions for estimating turbine speed based on engine speed and an estimated torque converter slip.

20. The computer readable storage medium of claim 18 further comprising:

instructions for determining a transmission pump loss based on the engine speed and a requested transmission hydraulic line pressure; and

wherein the instructions for determining a desired engine torque include instructions for determining the desired engine torque based at least in part on the transmission pump loss.

21. The computer readable storage medium of claim 18 wherein the instructions for determining a desired engine torque during a ratio change comprise:

instructions for determining a first engine torque based on the selected gear, the selected gear ratio, the torque proportional loss, and the transmission spin loss;

instructions for determining a second torque proportional loss based on a target gear and a second turbine speed wherein the second turbine speed is based on a target gear ratio and output shaft speed;

instructions for determining a second transmission spin loss based on the target gear and the second turbine speed;

instructions for determining a second engine torque based on the second torque proportional loss, the second spin loss and the target gear ratio; and

instructions for determining the desired engine torque based on the first and second engine torques.

22. The computer readable storage medium of claim 18 further comprising:

instructions for determining a torque ratio based on engine speed and engine inertia during a ratio change; and

instructions for adjusting spark based on the torque ratio for a predetermined time after the ratio change has been commanded to reduce actual engine torque during the ratio change.

23. A computer readable storage medium having stored data representing instructions executable by a computer to control a powertrain having an internal combustion engine and an automatic transmission, the computer readable storage medium comprising:

instructions for determining a desired wheel torque;

instructions for determining engine speed;

instructions for determining turbine speed;

instructions for determining a selected gear and associated selected gear ratio;

instructions for determining a transmission spin loss based on a first function of the turbine speed and the selected gear;

instructions for determining a transmission torque proportional loss based on turbine torque and a second function of the turbine speed and the selected gear;

instructions for determining desired engine torque based on the transmission spin loss, the transmission torque proportional loss, the selected gear ratio, the desired wheel torque, wheel speed, engine speed, and torque converter slip when vehicle speed exceeds a corresponding threshold;

instructions for determining the desired engine torque based on the transmission spin loss, the transmission torque proportional loss, the selected gear ratio, the desired wheel torque, the selected gear ratio, engine speed, and the torque converter slip when the vehicle speed does not exceed the corresponding threshold; and

instructions for controlling the powertrain using the desired engine torque such that actual wheel torque approaches the desired wheel torque.

24. A computer readable storage medium having stored data representing instructions executable by a computer to control a powertrain having an internal combustion engine and an automatic transmission, the computer readable storage medium comprising:

instructions for determining a desired wheel torque;

instructions for determining engine speed;

instructions for determining turbine speed;

instructions for determining a selected gear and associated selected gear ratio;

instructions for determining a transmission spin loss based on a first function of the turbine speed and the selected gear;

instructions for determining a transmission torque proportional loss based on turbine torque and a second function of the turbine speed and the selected gear;

instructions for determining desired engine torque based on the transmission spin loss, the transmission torque proportional loss, the selected gear ratio, wheel speed, the desired wheel torque, the engine speed, and the turbine speed when vehicle speed exceeds a corresponding threshold;

instructions for determining the desired engine torque based on the transmission spin loss, the transmission torque proportional loss, the selected gear ratio, the desired wheel torque, the selected gear ratio, the engine speed, and the turbine speed when the vehicle speed does not exceed the corresponding threshold; and

instructions for controlling the powertrain using the desired engine torque such that actual wheel torque approaches the desired wheel torque.