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Research pertaining to electronically controllable AWD (All Wheel Drive) systems continues in the automotive industry as a means to further enhance vehicle traction, maneuverability, handling and stability characteristics. Different feed-forward and feedback control approaches have also been explored to enhance AWD system performance and robustness under various vehicle operating conditions. Due to the large variability of vehicle operational conditions, some trade-off usually needs to be made to achieve a balanced overall-AWD system performance, especially traction and maneuverability for both normal flat roads and hill climbing conditions. The purpose of this research is to develop a hill grade detection method and strategy for application in vehicle front to rear drive torque distribution control to enhance AWD system robustness while climbing low-mu hills. First, an overview of existing vehicle hill climbing related drive torque control approaches are presented.

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.