Stability-enhanced traction control with electrically controlled center coupler

Abstract

A control system for a vehicle having first and second axles is provided that includes a coupling apparatus adapted to distribute torque between the first and second axles 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 coupling 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 coupling 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary all-wheel-drive vehicle drive-train configuration.

FIG. 2 is an exemplary electronically controlled coupling apparatus for use in a control system according to an embodiment of the present invention.

FIG. 3 illustrates the dynamics of an exemplary vehicle employing an electronically controlled center coupling apparatus and the effect on vehicle yaw control when disengaging and engaging the electronically controlled center coupling apparatus.

FIG. 4 is a schematic illustration of a control system according to an embodiment of the present invention.

FIG. 5 is a schematic illustration of an electronic control unit according to an embodiment of the present invention for use in the control system of FIG. 4.

FIGS. 6 and 7 graphically illustrate a performance comparison for an on-throttle vehicle turning maneuver on a low friction surface for a vehicle employing a center coupler.

FIGS. 8 and 9 graphically illustrate a performance comparison for an on-throttle turning maneuver on a low friction surface using a vehicle employing a center coupler.

FIGS. 10 and 11 graphically illustrate a performance comparison for an on-throttle T-junction vehicle launch using a vehicle employing a control system according to an embodiment of the present invention.

Claims

1. A control system for a vehicle having first and second axles comprising: a coupling apparatus adapted to distribute torque between the first and second axles;a traction controller for controlling operation of the coupling apparatus from vehicle launch up to a predetermined vehicle speed, the traction controller configured to engage the coupling 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 coupling 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.

2. The control system of claim 1, wherein the traction controller is configured to modulate engagement of the coupling 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 64 is configured to engage the coupling apparatus according to a desired coupling applied torque signal that is based on a modified normal coupling applied torque signal.

4. The control system of claim 3, wherein the desired coupling applied torque signal is equal to the normal coupling applied torque signal multiplied by a modifier, the modifier including in its numerator the difference between a predetermined maximum yaw rate difference and the multiplication of 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 predetermined maximum yaw rate difference.

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.

6. The control system of claim 1, further including a stability controller 66 for controlling engagement of the coupling apparatus at or above the predetermined vehicle speed.