System and method for minimizing shift cycling for engine operation using cruise control

Patent metadata

Field	Value
Publication number	US-9896099-B2
Application number	US-201514744904-A
Country	US
Kind code	B2
Filing date	Jun 19, 2015
Priority date	Jun 19, 2015
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

A system and method for minimizing shift cycling for low speed engine operation with a vehicle cruise control. A vehicle control system operating in a cruise control mode determines a deficiency in vehicle speed between a measured vehicle speed and a cruise set speed. The deficiency is determined by comparing the vehicle speed to the cruise set speed, and includes using the compared valued to find a cruise speed margin, which is continuously updated. While the cruise control system is active, the control system logic determines the time at which a transmission upshift occurs based on the cruise speed margin. The vehicle speed, at which the upshift is made, is determined as a function of the updated cruise speed margin. An upshift is not made, if a likely drop in vehicle speed would result in the event a downshift would occur once the upshift is made.

First claim

The invention claimed is:

1. A vehicle speed control method for controlling a speed of a vehicle including a cruise control system and an engine developing an engine torque to drive a transmission having a plurality of gears, wherein the transmission is configured to upshift from a lower gear to a higher gear having a lower RPM than an RPM of the lower gear, is configured to downshift from the higher gear to the lower gear having a higher RPM than the RPM of the higher gear, and is configured to move the vehicle in response to the engine torque, the method comprising:
detecting if the vehicle is operating with a cruise set speed maintained by the cruise control system;
detecting when the vehicle speed is less than the cruise set speed, if the vehicle is operating with the cruise control set speed;
determining a cruise margin from a comparison of the vehicle speed to the cruise set speed, if the detected vehicle speed is less than the cruise set speed;
modifying the cruise margin over a period of time;
shifting from the lower gear to the higher gear if the vehicle speed is greater than the modified cruise margin; and
not shifting from the lower gear to the higher gear if the vehicle speed is less than the modified cruise margin.

2. The vehicle speed control method of claim 1 wherein the modifying the cruise margin includes increasing the modified cruise margin when the difference between the cruise set speed and the vehicle speed is greater than the modified cruise margin.

3. The vehicle speed control method of claim 2 wherein the modifying the cruise margin includes decreasing the modified cruise margin over time.

4. The vehicle speed control method of claim 3 wherein the decreasing the modified cruise margin over the period of time includes decreasing a value of the modified cruise margin over time until the modified cruise margin reaches a predetermined value.

5. The vehicle speed control method of claim 4 includes determining the predetermined value prior to the detecting if the vehicle is operating with the cruise set speed established by the cruise control system.

6. The vehicle speed control method of claim 4 includes determining the predetermined value once the vehicle is operating with the cruise set speed established by the cruise control system.

7. The vehicle speed control method of claim 3 wherein the decreasing the modified cruise margin over time includes continuously decreasing the cruise margin over time until the modified cruise margin reaches one of i) a predetermined value and ii) the cruise set speed minus the vehicle speed is greater than the modified cruise margin.

8. The vehicle speed control method of claim 7 further including increasing the modified cruise margin if the vehicle speed is greater than the modified cruise margin and the engine of the vehicle is not torque limited.

9. The vehicle speed control method of claim 8 further including downshifting from the higher gear to the lower gear if the vehicle speed in the higher gear falls below a downshift speed threshold.

10. The vehicle speed control method of claim 9 further including upshifting from the lower gear to the higher gear if the vehicle speed is greater than the modified cruise margin.

11. A vehicle speed control method for controlling a speed of a vehicle including a cruise control system and an engine developing an engine torque to drive a transmission having a plurality of gears, wherein the transmission is configured to upshift from a lower gear to a higher goat having a lower RPM than an RPM of the lower gear and is configured to downshift from the higher gear to the lower gear having a higher RPM than the RPM of the higher gear, the method comprising:
generating a first cruise margin when a vehicle speed is less than a cruise control set speed;
generating a second cruise margin when a difference between the cruise control set speed and the vehicle speed is greater than the first cruise margin;
decreasing the value of the second cruise margin over time until the second cruise margin is equal to a predetermined cruise margin.

12. The vehicle speed control method of claim 11 further comprising downshifting from the higher gear to the lower gear when the first cruise margin is generated and the engine is torque limited.

13. The vehicle speed control method of claim 12 further comprising upshifting from the lower gear to the higher gear when the vehicle speed is greater than the second cruise margin and the upshifting from the lower gear to the higher gear does not torque limit the engine.

14. The vehicle speed control method of claim 13 wherein the decreasing the value of the second cruise margin over time includes decreasing the value as a function of one of an exponential decay, a linear decay, and a stepwise decay.

15. The vehicle speed control method of claim 14 further comprising generating a third cruise margin if the difference between the cruise set speed and the vehicle speed is greater than the second cruise margin and thy: second cruise margin is not equal to the predetermined cruise margin.

16. The vehicle speed control method of claim 15 further comprising decreasing the third cruise margin over time.

17. A vehicle control system configured to control a vehicle speed of a vehicle including a cruise control system configured to provide a cruise set speed, an engine developing an engine torque to drive a transmission having a plurality of gears, wherein the transmission is configured to upshift from a lower gear to a higher gear having a lower RPM than an RPM of the lower gear, is configured to downshift from the higher gear to the lower gear having a higher RPM than the RPM of the higher gear, and is configured to move the vehicle in response to the engine torque, the vehicle control system including:
a memory device configured to store program instructions; and
a vehicle system control module operably connected to the transmission and to the memory device, the vehicle system control module configured to execute the stored program instructions to:
generate a first cruise margin when the vehicle speed is less than the cruise set speed;
generate a second cruise margin when a difference between the cruise set speed and the vehicle speed is greater than the first cruise margin;
modify the second cruise margin over time; and
control a shift from the lower gear to the higher gear or from the higher gear to the lower gear based on the modified second cruise margin.

18. The vehicle control system of claim 17 wherein the vehicle system controller is configured to execute the stored program instructions to:
decrease the value of the second cruise margin over time until the second cruise margin is equal to a predetermined cruise margin value.

19. The vehicle control system of claim 18 wherein the vehicle system controller is configured to execute the stored program instructions to:
shift the transmission from the higher gear to the lower gear when the first cruise margin is generated and the engine is torque limited.

20. The vehicle control system of claim 18 wherein the vehicle system controller is further configured to execute the stored program instructions to:
upshift the transmission from the lower gear to the higher gear when vehicle speed is greater than the second cruise margin and the upshift to the higher gear does not torque limit the engine.

21. The vehicle control system of claim 20 wherein the vehicle system controller is configured to execute the stored progr

Assignees

• Allison Transm Inc
• Allison Transm Inc

Inventors

• West Stephen

Classifications

• B60W50/06

  Improving the dynamic response of the control system, e.g. improving the speed of regulation or avoiding hunting or overshoot · CPC title

• B60W30/143 Primary

  Speed control (B60W30/16 takes precedence) · CPC title

• B60W2720/10

  Longitudinal speed · CPC title

• F16H61/10

  Controlling shift hysteresis · CPC title

• B60Y2300/143

  Speed control · CPC title