Stability-enhanced traction and yaw control using electronically controlled limited-slip differential

Abstract

A control system for a vehicle having first and second wheels is provided that includes a differential apparatus adapted to distribute torque between the first and second wheels and a traction controller for controlling operation of the differential apparatus from vehicle launch up to a predetermined vehicle speed. The traction controller is configured to engage the differential apparatus in a first operating state according to at least one vehicle operating parameter indicative of a low traction operating condition and to further control engagement of the differential apparatus in a second vehicle operating state during the low traction operating condition according to a difference between an actual vehicle yaw rate and a predetermined target vehicle yaw rate. The control system also includes a stability controller for controlling engagement of the differential apparatus at or above the predetermined vehicle speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary vehicle driveline configuration including an electronically controlled limited-slip differentials;

FIG. 2 is a cross-sectional view of an exemplary electronically controlled limited-slip differential;

FIG. 3 is a plot of clutch response time for the exemplary electronically controlled limited-slip differential shown in FIG. 2;

FIG. 4 is a dynamic model of a vehicle axle including an electronically controlled limited-slip differential;

FIG. 5 is a dynamic model of an electronically controlled limited-slip differential clutch;

FIG. 6 is schematic diagram of a control system according to an embodiment of the present invention;

FIG. 7 is a plot showing the effect of locking an electronically controlled limited-slip differential on the rear wheels of a vehicle axle;

FIG. 8 is a plot of vehicle yaw rate for a double lane change maneuver in a vehicle including a control system according to an embodiment of the present invention;

FIG. 9 is a plot of clutch torque for an electronically controlled limited-slip differential corresponding to the plot of FIG. 8;

FIG. 10 is a composite snap-shot of a vehicle animation run corresponding to the plot of FIG. 8;

FIGS. 11-13 illustrate test results, in graphical format, of vehicle performance during launch using a control system according to an embodiment of the present invention;

FIGS. 14-22 illustrate test results, in graphical format, of vehicle performance during a relatively high-speed slalom maneuver using a control system according to an embodiment of the present invention; and

FIGS. 23 and 24 illustrate test results, in graphical format, of vehicle performance during an open-loop, sine-steer maneuver on a packed-snow road surface using a control system according to an embodiment of the present invention.

Claims

1. A control system for a vehicle having first and second wheels, comprising: a differential apparatus adapted to distribute torque between the first and second wheels;a stability-enhanced traction controller for controlling operation of the differential apparatus from vehicle launch up to a predetermined vehicle speed, the traction controller configured to engage the differential apparatus in a first vehicle operating state according to at least one vehicle operating parameter indicative of a low traction operating condition and to further control engagement of the differential apparatus in a second vehicle operating state during the low traction operating condition according to a difference between an actual vehicle yaw rate and a predetermined target vehicle yaw rate; anda stability controller for controlling engagement of the differential apparatus at or above the predetermined vehicle speed.

2. The control system of claim 1, wherein the traction controller is configured to modulate engagement of the differential apparatus during the low traction operating condition according to a difference between the actual vehicle yaw rate and the predetermined target vehicle yaw rate.

3. The control system of claim 1, wherein the traction controller is configured to engage the differential apparatus according to a desired differential applied torque signal that is based on a modified original differential applied torque signal.

4. The control system of claim 3, wherein the desired differential applied torque signal is equal to the original differential applied torque signal multiplied by a modifier, the modifier including in its numerator the difference between an error range value and the multiplication of a saturation function, a deadband and the difference between the actual vehicle yaw rate and the predetermined target vehicle yaw rate, and the modifier including in its denominator the error range value.

5. The control system of claim 1, wherein in the first vehicle operating state, the actual vehicle yaw rate is less than or substantially equal to the predetermined target vehicle yaw rate, and in the second vehicle operating state, the actual vehicle yaw rate is greater than the predetermined target vehicle yaw rate.