Torque security of MPC-based powertrain control

• US 10,125,712 B2
• Filed: 02/17/2017
• Issued: 11/13/2018
• Est. Priority Date: 02/17/2017
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Livshiz, Michael, Pattipati, Bharath, Worthing, James L, Whitney, Christopher E
• Primary Examiner(s): Pang, Roger L
• Application Number:
  US15/436,235
• Publication Number:
  US 20180238257A1
• Time in Patent Office: 634 Days
• Field of Search: 701101
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 30/184 Preventing damage resulting from overload or excessive wear of the driveline
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power
• CPC Class Codes: F02D 2041/1412 using a predictive controller
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/1004 Estimation of the output torque
• CPC Class Codes: F02D 2200/501 Vehicle speed
• CPC Class Codes: F02D 2200/602 Pedal position
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2250/26 by applying a torque limit
• CPC Class Codes: F02D 29/02 peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers
• CPC Class Codes: F02D 41/1406 with use of a optimisation method, e.g. iteration
• CPC Class Codes: F02D 41/20 Output circuits, e.g. for controlling currents in command coils
• CPC Class Codes: F02D 41/263 the program execution being modifiable by physical parameters
• CPC Class Codes: F16H 63/50 Signals to an engine or motor
• CPC Class Codes: G05B 13/048 using a predictor

Abstract

A propulsion system, control system, and method are provided that use model predictive control to generate an initial selected engine output torque value. A minimum torque limit is determined by selecting a minimum acceptable engine output torque. A maximum torque limit is determined by selecting a maximum acceptable engine output torque. A desired engine output torque value is set as: a) the minimum torque limit, if the initial selected engine output torque value is less than the minimum torque limit; b) the maximum torque limit, if the initial selected engine output torque value is greater than the maximum torque limit; or c) the initial selected engine output torque value, if the initial selected engine output torque value is neither greater than the maximum torque limit nor less than the minimum torque limit.

Claims

1. A method for controlling a propulsion system of a motor vehicle, the method comprising:

determining an initial selected engine output torque value using a model predictive control system;

determining at least one of a first minimum acceptable engine output torque and a second minimum acceptable engine output torque, the first minimum acceptable engine output torque being based on an engine output torque requested and a predetermined engine output torque minimum constant, and the second minimum acceptable engine output torque being based on an axle torque requested and a predetermined axle torque minimum constant;

determining a minimum torque limit by selecting one of the first and second minimum acceptable engine output torques;

determining whether the initial selected engine output torque value is less than the minimum torque limit;

if the initial selected engine output torque value is less than the minimum torque limit, setting a desired engine output torque value as the minimum torque limit;

determining at least one of a first maximum acceptable engine output torque and a second maximum acceptable engine output torque, the first maximum acceptable engine output torque being based on the engine output torque requested and a predetermined engine output torque maximum constant, and the second maximum acceptable engine output torque being based on the axle torque requested and a predetermined axle torque maximum constant;

determining a maximum torque limit by selecting one of the first and second maximum acceptable engine output torques;

determining whether the initial selected engine output torque value is greater than the maximum torque limit;

if the initial selected engine output torque value is greater than the maximum torque limit, setting the desired engine output torque value as the maximum torque limit; and

if the initial selected engine output torque value is neither greater than the maximum torque limit nor less than the minimum torque limit, setting the desired engine output torque value as the initial selected engine output torque value.

2. The method of claim 1, wherein:

the step of determining at least one of a first minimum acceptable engine output torque and a second minimum acceptable engine output torque includes determining both of the first and second minimum acceptable engine output torques;

the step of determining the minimum torque limit includes selecting the lower of the first and second minimum acceptable engine output torques;

the step of determining at least one of a first maximum acceptable engine output torque and a first maximum acceptable engine output torque includes determining both of the first and second maximum acceptable engine output torques; and

the step of determining the maximum torque limit includes selecting the greater of the first and second maximum acceptable engine output torques.

3. The method of claim 2, further comprising:

determining the first minimum acceptable engine output torque (Te_1_acc_min) by subtracting the predetermined engine output torque minimum constant from the engine output torque requested;

determining the first maximum acceptable engine output torque (Te_1_acc_max) by adding the predetermined engine output torque maximum constant to the engine output torque requested;

determining the second minimum acceptable engine output torque (Te_2_acc_min) with the following equation;

4. The method of claim 3, further comprising:

determining whether the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for a predetermined failure time period; and

if the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for the predetermined failure time period, setting a failure mode output as true.

5. The method of claim 4, further comprising setting the desired engine output torque value as the engine output torque requested if the failure mode output is true.

6. The method of claim 5, further comprising:

determining an accelerator pedal position (PP);

determining a vehicle speed (V);

determining the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determining a transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determining the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and the final drive ratio (FD).

7. The method of claim 6, wherein the step of determining the initial selected engine output torque value using the model predictive control system comprises:

generating a plurality of sets of possible command values, the plurality of sets of possible command values including a plurality of commanded engine output torque values and a plurality of commanded transmission ratio values;

determining a cost for each set of possible command values of the plurality of sets of possible command values based on a first predetermined weighting value, a second predetermined weighting value, a predicted actual axle torque value of a plurality of predicted actual axle torque values, a predicted actual fuel consumption rate value of a plurality of predicted actual fuel consumption rate values, the axle torque requested, the engine output torque requested, the transmission ratio requested, and a fuel consumption rate requested;

determining which set of possible command values of the plurality of sets of possible command values has a lowest cost; and

selecting the set of possible command values that has the lowest cost to define a selected set, the selected set including the initial selected engine output torque value and a selected transmission ratio value.

8. The method of claim 7, further comprising controlling a vehicle parameter based on the desired engine output torque value and the selected transmission ratio value.

9. A motor vehicle propulsion control system for a motor vehicle having a transmission and an engine, the motor vehicle propulsion control system comprising:

a model predictive control module configured to determine an initial selected engine output torque value using a model predictive control scheme;

a torque security monitor module configured to;

determine at least one of a first minimum acceptable engine output torque and a second minimum acceptable engine output torque, the first minimum acceptable engine torque being based on an engine output torque requested and a predetermined engine output torque minimum constant, and the second minimum acceptable engine output torque being based on an axle torque requested and a predetermined axle torque minimum constant;

determine a minimum torque limit by selecting one of the first and second minimum acceptable engine output torques;

determine whether the initial selected engine output torque value is less than the minimum torque limit;

set a desired engine output torque value as the minimum torque limit if the initial selected engine output torque value is less than the minimum torque limit;

determine at least one of a first maximum acceptable engine output torque and a second maximum acceptable engine output torque, the first maximum acceptable engine torque being based on the engine output torque requested and a predetermined engine output torque maximum constant, and the second maximum acceptable engine output torque being based on the axle torque requested and a predetermined axle torque maximum constant;

determine a maximum torque limit by selecting one of the first and second maximum acceptable engine output torques;

determine whether the initial selected engine output torque value is greater than the maximum torque limit;

set the desired engine output torque value as the maximum torque limit if the initial selected engine output torque value is greater than the maximum torque limit; and

set the desired engine output torque value as the initial selected engine output torque value if the initial selected engine output torque value is neither greater than the maximum torque limit nor less than the minimum torque limit.

10. The motor vehicle propulsion control system of claim 9, wherein the torque security monitor module is configured to:

determine both of the first and second minimum acceptable engine output torques;

determine both of the first and second maximum acceptable engine output torques;

determine the minimum torque limit by selecting the lower of the first and second minimum acceptable engine output torques; and

determine the maximum torque limit by selecting the greater of the first and second maximum acceptable engine output torques.

11. The motor vehicle propulsion control system of claim 10, wherein the torque security monitor module is configured to:

determine the first minimum acceptable engine output torque (Te_1_acc_min) by subtracting the predetermined engine output torque minimum constant from the engine output torque requested;

determine the first maximum acceptable engine output torque (Te_1_acc_max) by adding the predetermined engine output torque maximum constant to the engine output torque requested;

determine the second minimum acceptable engine output torque (Te_2_acc_min) with the following equation;

12. The motor vehicle propulsion control system of claim 11, wherein the torque security monitor module is configured to determine whether the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for a predetermined failure time period, the torque security monitor module being configured to set a failure mode output as true if the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for the predetermined failure time period, the torque security monitor module being configured to set the desired engine output torque value as the engine output torque requested if the failure mode output is true.

13. The motor vehicle propulsion control system of claim 12, further comprising a steady state optimizer module configured to:

determine an accelerator pedal position (PP);

determine a vehicle speed (V);

determine the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determine a transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determine the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and the final drive ratio (FD).

14. The motor vehicle propulsion control system of claim 13, wherein the model predictive control module is configured to determine the initial selected engine output torque value by:

generating a plurality of sets of possible command values, the plurality of sets of possible command values including a plurality of commanded engine output torque values and a plurality of commanded transmission ratio values;

determining a cost for each set of possible command values of the plurality of sets of possible command values based on a first predetermined weighting value, a second predetermined weighting value, a predicted actual axle torque value of a plurality of predicted actual axle torque values, a predicted actual fuel consumption rate value of a plurality of predicted actual fuel consumption rate values, the axle torque requested, the engine output torque requested, the transmission ratio requested, and a fuel consumption rate requested;

determining which set of possible command values of the plurality of sets of possible command values has a lowest cost; and

selecting the set of possible command values that has the lowest cost to define a selected set, the selected set including the initial selected engine output torque value and a selected transmission ratio value.

15. The motor vehicle propulsion control system of claim 14, further comprising an actuator module configured to control a vehicle parameter based on the desired engine output torque value and the selected transmission ratio value.

16. A propulsion system for a motor vehicle, comprising:

an engine operable to power the motor vehicle, the engine having an engine output shaft configured to transfer engine output torque;

a continuously variable transmission having a variator assembly including a first pulley and a second pulley, the first and second pulleys being rotatably coupled by a rotatable member, at least one of the first and second pulleys including a movable sheave translatable along an axis to selectively change a transmission ratio between the engine output shaft and a transmission output shaft;

a drive axle configured to be driven via the transmission output shaft, the drive axle being configured to output axle torque to a set of wheels; and

a control system comprising;

a model predictive control module configured to determine an initial selected engine output torque value using a model predictive control scheme;

a torque security monitor module configured to;

determine at least one of a first minimum acceptable engine output torque and a second minimum acceptable engine output torque, the first minimum acceptable engine output torque being based on an engine output torque requested and a predetermined engine output torque minimum constant, and the second minimum acceptable engine output torque being based on an axle torque requested and a predetermined axle torque minimum constant;

determine a minimum torque limit by selecting one of the first and second minimum acceptable engine output torques;

determine whether the initial selected engine output torque value is less than the minimum torque limit;

set a desired engine output torque value as the minimum torque limit if the initial selected engine output torque value is less than the minimum torque limit;

determine at least one of a first maximum acceptable engine output torque and a second maximum acceptable engine output torque, the first maximum acceptable engine output torque being based on the engine output torque requested and a predetermined engine output torque maximum constant, and the second maximum acceptable engine output torque being based on the axle torque requested and a predetermined axle torque maximum constant;

determine a maximum torque limit by selecting one of the first and second maximum acceptable engine output torques;

determine whether the initial selected engine output torque value is greater than the maximum torque limit;

set the desired engine output torque value as the maximum torque limit if the initial selected engine output torque value is greater than the maximum torque limit; and

set the desired engine output torque value as the initial selected engine output torque value if the initial selected engine output torque value is neither greater than the maximum torque limit nor less than the minimum torque limit.

17. The propulsion system of claim 16, wherein the torque security monitor module is configured to:

determine both of the first and second minimum acceptable engine output torques;

determine both of the first and second maximum acceptable engine output torques;

determine the minimum torque limit by selecting the lower of the first and second minimum acceptable engine output torques; and

determine the maximum torque limit by selecting the greater of the first and second maximum acceptable engine output torques.

18. The propulsion system of claim 17, wherein the torque security monitor module is configured to:

determine the first minimum acceptable engine output torque (Te_1_acc_min) by subtracting the predetermined engine output torque minimum constant from the engine output torque requested;

determine the first maximum acceptable engine output torque (Te_1_acc_max) by adding the predetermined engine output torque maximum constant to the engine output torque requested;

determine the second minimum acceptable engine output torque (Te_2_acc_min) with the following equation;

19. The propulsion system of claim 18, wherein the torque security monitor module is configured to determine whether the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for a predetermined failure time period, the torque security monitor module being configured to set a failure mode output as true if the desired engine output torque value is set as one of the minimum torque limit and the maximum torque limit for the predetermined failure time period, the torque security monitor module being configured to set the desired engine output torque value as the engine output torque requested if the failure mode output is true.

20. The propulsion system of claim 19, the control system further comprising a steady state optimizer module configured to:

determine an accelerator pedal position (PP);

determine a vehicle speed (V);

determine the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determine a transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determine the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and the final drive ratio (FD), wherein

the model predictive control module is configured to determine the initial selected engine output torque value by;

generating a plurality of sets of possible command values, the plurality of sets of possible command values including a plurality of commanded engine output torque values and a plurality of commanded transmission ratio values;

determining a cost for each set of possible command values of the plurality of sets of possible command values based on a first predetermined weighting value, a second predetermined weighting value, a predicted actual axle torque value of a plurality of predicted actual axle torque values, a predicted actual fuel consumption rate value of a plurality of predicted actual fuel consumption rate values, the axle torque requested, the engine output torque requested, the transmission ratio requested, and a fuel consumption rate requested;

determining which set of possible command values of the plurality of sets of possible command values has a lowest cost; and

selecting the set of possible command values that has the lowest cost to define a selected set, the selected set including the initial selected engine output torque value and a selected transmission ratio value,

wherein the control system further comprises an actuator module configured to control a vehicle parameter based on the desired engine output torque value and the selected transmission ratio value.