System and method for clutch pressure control

Patent metadata

Field	Value
Publication number	US-9803706-B2
Application number	US-201615201630-A
Country	US
Kind code	B2
Filing date	Jul 5, 2016
Priority date	Mar 13, 2013
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

A method for controlling clutch pressure in an electronically controlled limited slip differential comprises receiving a target clutch pressure command indicative of a desired differential torque transfer setting. Processing the target clutch pressure command comprises estimating one of a motor current or a motor speed, calculating an integrated error of a target motor current or an integrated error of a target motor speed, calculating gains over time based on the estimated motor current or the estimated motor speed and based on the integrated error of the target motor current or the integrated error of the target motor speed, applying the calculated gains thereby forming a closed loop feedback, and calculating an oscillation. The target motor current or the target motor speed is applied to a motor connected to a clutch in the differential according to the calculated oscillation to control the clutch pressure of the differential.

First claim

I claim:

1. A method for controlling clutch pressure in an electronically controlled limited slip differential, comprising:
receiving a target clutch pressure command indicative of a desired differential torque transfer setting;
processing the target clutch pressure command in a processing device comprising a processor, a memory, and processor-executable programming, the processing comprising:
estimating one of a motor current or a motor speed;
calculating an integrated error of a target motor current or an integrated error of a target motor speed;
processing the estimated motor current or the estimated motor speed and processing the integrated error of the target motor current or the integrated error of the target motor speed to calculate gains;
applying the calculated gains to the target motor current or to the target motor speed thereby forming a closed loop feedback; and
calculating an oscillation about the target motor current or about the target motor speed; and

applying the target motor current or the target motor speed to a motor connected to a clutch in the differential according to the calculated oscillation to control the clutch pressure of the differential.

2. The method of claim 1 , further comprising processing an amplitude of the integrated error of the target motor current or processing the integrated error of the target motor speed to calculate an adjustment to the calculated oscillation.

3. The method of claim 1 , further comprising processing a difference between a measured clutch pressure and the target clutch pressure to adjust a gain factor.

4. The method of claim 1 , wherein the differential is a hydraulic differential, and wherein the motor pumps hydraulic fluid to the clutch, and the method further comprises setting a cracking pressure of a relief valve coupled to the differential greater than the maximum operating pressure of the clutch, and applying the target motor current or the target motor speed to supply hydraulic fluid pressure to the clutch such that the hydraulic fluid flows through the relief valve during steady state motor operation.

5. The method of claim 1 , wherein the differential is a hydraulic differential, and wherein the motor pumps hydraulic fluid to the clutch, and the method further comprises applying the target motor current or the target motor speed to supply hydraulic fluid pressure to a two-way valve coupled to the clutch such that the hydraulic fluid flows bleeds back from the clutch and through the two-way valve during steady state motor operation.

6. The method of claim 1 , wherein the differential is a hydraulic differential, and wherein the motor pumps hydraulic fluid to the clutch, and the method further comprises:
providing hydraulic fluid at a prefill target speed when the target clutch pressure command indicates a transition from an idle clutch state to an active clutch state;
iteratively measuring the actual clutch pressure during the transition;
comparing the actual clutch pressure to the target clutch pressure commanded iteratively during the transition; and
when the actual clutch pressure is equal to the target clutch pressure commanded multiplied by a prefill target ratio, ramping the prefill target speed towards a steady state speed.

7. The method of claim 1 , wherein the differential is a hydraulic differential comprising an electronically controlled pressure valve controlled by a valve pressure controller, wherein the motor pumps hydraulic fluid to the clutch via the pressure valve, and wherein the valve pressure controller comprises a respective processing device comprising a respective processor, a respective memory, and respective processor-executable programming, the method further comprises:
receiving a target clutch pressure command indicative of a desired differential torque transfer setting;
processing the target clutch pressure command;
processing feedback measured from the pressure valve to estimate a valve resistance of the pressure valve; and
applying the estimated valve resistance as a feed forward term to the processed target clutch pressure command to output a valve duty cycle command.

8. The method of claim 7 , wherein the estimating of the valve resistance comprises recursive least squares estimation.

9. The method of claim 7 , wherein the processing of the target clutch pressure command comprises a sliding mode adjustment to force the result of the output valve duty cycle command towards the target clutch pressure command.

10. The method of claim 9 , wherein processing the target clutch pressure command comprises processing an error signal to result in the sliding mode adjustment, and the method further comprises applying a counter to the sliding mode adjustment, comparing the counter to a threshold, and when the threshold is exceeded, the sliding mode adjustment is changed regardless of whether the error signal indicates a need for change.

11. The method of claim 7 , wherein the processing of the target clutch pressure command comprises calculation and application of gains to the target clutch pressure command.

12. A method of controlling clutch pressure in an electronically controlled hydraulic limited slip differential, comprising:
receiving a target clutch pressure command indicative of a desired differential torque transfer setting;
receiving a measured hydraulic pressure and a measured temperature of hydraulic fluid used to control a clutch of the differential;
processing the received pressure and temperature to convert the target clutch pressure command, into a motor speed control command or a motor duty cycle command by applying one of a proportional integral derivative (PID) calculation and a linear quadratic regulator (LQR) calculation while carrying out a closed loop control;
applying the motor speed control command or the motor duty cycle command to a motor supplying hydraulic fluid to the clutch;
converting the target clutch pressure command, based on the received pressure and temperature, in to a valve pressure command by applying control gain adaptation and by applying a sliding mode calculation, while carrying out open loop pressure control;
applying the valve pressure command to a pressure control valve connected to the clutch;
measuring the actual clutch pressure resulting from the applied valve pressure command and resulting from the applied motor speed control command and the applied motor duty cycle command; and
applying the measured actual clutch pressure to the closed loop control and to the open loop pressure control.

13. The method of claim 12 , further comprising limiting the motor speed control command to operate a hydraulic fluid pump at a minimum speed necessary to provide hydraulic fluid at a pressure that exceeds a leakage pressure of the pressure control valve.

14. The method of claim 12 , wherein the motor speed control command operates a hydraulic fluid pump at a first speed to prefill the clutch, and the method further comprises ramping the motor speed control command when a threshold prefilling of the clutch has occurred.

15. The method of claim 12 , further comprising:
processing the target clutch pressure command, feedback of the measured actual clutch pressure, and the measured temperature of the hydraulic fluid to calculate gain values;
applying the calculated gain values to a sliding mode controller and to a proportional integral derivative (PID) controller; and
combining the results of the applied calculated gain values to convert the target clutch pressure command in to the valve pressure command.

16. The method of claim 15 , further compri

Assignees

• Eaton Corp

Inventors

• Chimner Christian Thomas

Classifications

• F16D2500/70605

  Adaptive correction; Modifying control system parameters, e.g. gains, constants, look-up tables · CPC title

• F16D2500/1024

  combined with hydraulic actuation · CPC title

• F16D2500/1026

  Hydraulic · CPC title

• F16D48/066 Primary

  Control of fluid pressure, e.g. using an accumulator (F16D48/062, F16D48/068 take precedence) · CPC title

• F16D2500/70626

  PID control · CPC title