Control system and method

• US 10,144,422 B2
• Filed: 02/18/2015
• Issued: 12/04/2018
• Est. Priority Date: 02/19/2014
• Status: Active Grant

• Current Assignee: Jaguar Land Rover Limited (TATA Motors Limited)
• Original Assignee: Jaguar Land Rover Limited (TATA Motors Limited)
• Inventors: Jerger, Rob, Woodley, Jonathan
• Primary Examiner(s): Pang, Roger L
• Application Number:
  US15/120,095
• Publication Number:
  US 20170057506A1
• Time in Patent Office: 1,385 Days
• Field of Search: 701 55, 701 56, 701 58, 701 65
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 2520/26 Wheel slip
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2552/40 Coefficient of friction
• CPC Class Codes: B60W 2710/0644 Engine speed
• CPC Class Codes: B60W 2710/105 Output torque
• CPC Class Codes: B60W 30/143 Speed control B60W30/16 takes precedence
• CPC Class Codes: B60W 30/18172 Preventing, or responsive to skidding of wheels
• CPC Class Codes: B60Y 2300/143 Speed control
• CPC Class Codes: F16H 2059/506 Wheel slip
• CPC Class Codes: F16H 2061/0239 Selecting ratios for preventing or cancelling wheel slip
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals
• CPC Class Codes: F16H 61/16 Inhibiting or initiating shift during unfavourable conditions, e.g. preventing forward reverse shift at high vehicle speed, preventing engine over speed unintentional control input F16H61/18

Abstract

Embodiments of the present invention provide a system comprising: a first controller configured in each of a predetermined plurality of states to generate a torque request signal in order to cause a vehicle to operate in accordance with a target speed value, the system being configured, when the first controller is one of said plurality of states to generate a gear shift limit signal to cause a change in an engine speed at which a transmission controller is permitted to cause a gear downshift, the gear shift limit signal being generated in dependence on at least one traction indicator signal indicative of an amount of estimated traction between the vehicle and a driving surface.

Claims

1. A system comprising:

a first controller configured in each of a predetermined plurality of states to generate a torque request signal in order to cause a vehicle to operate in accordance with a target speed value,

the system being configured, when the first controller is one of said predetermined plurality of states operating in accordance with the target speed value, to generate a gear shift limit signal to cause a change in an engine speed at which a transmission controller is permitted to cause a gear downshift, the gear shift limit signal being generated in dependence on at least one traction indicator signal indicative of an amount of estimated traction between the vehicle and a driving surface, wherein the gear shift signal is further configured to suspend a gear downshift when the estimated traction between the vehicle and the driving surface is below a first threshold.

2. A system according to claim 1 wherein suspending a gear downshift comprises reducing the engine speed at which a transmission controller is permitted to cause a gear downshift to substantially zero, while the vehicle is in motion.

3. A system according to claim 1 wherein the gear shift limit signal is configured to reduce the engine speed at which the transmission controller causes a downshift.

4. A system according to claim 1 wherein the gear shift limit signal is configured to substantially prevent the transmission controller from causing a downshift by reducing the engine speed at which a transmission controller causes a downshift.

5. A system according to claim 1 wherein the at least one traction indicator signal is a signal indicative of one or more of:

a normal force between a wheel and the driving surface;

an amount of torque that may be applied to a wheel before slip of the wheel occurs; and

a surface coefficient of friction between a wheel and the driving surface.

6. A system according to claim 1 wherein the first controller is configured to perform a mu-check operation when in one of the plurality of states, the system being configured to perform the mu-check operation by causing the transmission controller to cause a downshift and monitoring a speed of one or more wheels in response to the downshift.

7. A system according to claim 6 wherein when performing the mu-check operation the first controller is configured to calculate an estimated value of surface coefficient of friction between a wheel and the driving surface in dependence on a change in a speed of one or more wheels in response to the downshift.

8. A system according to claim 6 configured to perform the mu-check operation when one or more predetermined conditions are met during operation in one of said plurality of states.

9. A system according to claim 8 configured to perform the mu-check at predetermined intervals of time.

10. A system according to claim 5 configured to perform a mu-check following a torque control intervention event in which a torque intervention system intervenes to cause change in an amount of torque applied to one or more wheels.

11. A system according to claim 1 wherein the at least one traction indicator signal is indicative of an amount of torque that may be applied to a wheel before slip of the wheel slip exceeding a predetermined amount occurs.

12. A system according to claim 1 further configured, when causing a vehicle to operate in accordance with the target speed value, to generate a brake request signal to command a brake system to deliver an amount of brake torque.

13. A system according to claim 12 wherein said plurality of states includes a first state in which the system is configured to generate a powertrain request signal in order to cause a powertrain to deliver drive torque and cause the vehicle to operate in accordance with the target speed value, and a second state wherein the system is configured to cause the vehicle to operate in accordance with the target speed value by generating the brake request signal and not to generate the powertrain request signal in order to cause the powertrain to deliver drive torque.

14. A motor vehicle comprising a system according to claim 1.

15. A vehicle according to claim 14 further comprising a chassis, a body attached to said chassis, a plurality of wheels, a powertrain to drive said wheels, and a braking system to brake said wheels.

16. A method of operating a vehicle implemented by means of a control system, the method comprising:

causing a powertrain to deliver drive torque and cause a vehicle to operate in accordance with a target speed value;

while operating in accordance with the target speed value, generating a gear shift signal to cause a change in a speed at which a transmission is permitted to downshift or substantially prevent a transmission from downshifting, and

generating the gear shift signal in dependence on at least one traction indicator signal being a signal indicative of an amount of tractive force that may he developed between a driving surface and one or more driving wheels, wherein the gear shift limit signal is further configured to suspend a gear downshift when the estimated traction between the vehicle and the driving surface is below a first threshold.

17. A non-transient carrier medium carrying computer readable code for controlling a vehicle to carry out the method of claim 16.

18. A computer program product executable on a processor so as to implement the method of claim 16.

19. A computer readable medium loaded with the computer program product of claim 17.

20. A processor having an associated memory with instructions stored therein, the processor arranged to access the memory and execute instructions stored therein so as to implement the method of claim 16.