Method for Improved Yaw Stabilization Control by Integration of a Direct Yaw Control AWD System with a Vehicle Stability Assist Controller 2008-01-1456

In order to advance vehicle stability control strategies and provide enhanced customer benefits, a methodology for combining the capabilities of an active driveline system capable of direct yaw control with a vehicle stability assist controller (also referred to as ESC, electronic stability control) has been developed. As a basis, the traditional ESC operation of using only brake and throttle control is compared and contrasted against customer needs and expectations. Using the existing ESC stability control system as a representative yaw stability control algorithm, the actuation capabilities of a controllable AWD system are arranged through a simple CAN communication scheme to serve as an available extension to the ESC actuator set (i.e. brake, throttle and now AWD direct yaw moment control). The ESC unit is allowed to request a rear axle torque amount change to the controllable AWD unit ECU. Inside the AWD unit ECU this request is integrated with feed-forward control logic that the AWD system concurrently executes to respond to the operator's driving intention. A viewpoint towards cooperation rather than unified control integration is adopted to allow the driver to retain maneuverability, even during a lengthy ESC activation period. In addition, the cooperative structure allows each unit (ESC or AWD) to establish control of their own failsafe methodology while still allowing for integrated control. The benefits of this control structure on low surface coefficient driving conditions are shown as examples.