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The research described in this paper aimed to study the cornering resistance and dissipation power on the tire contact patch, and to develop an efficient direct yaw moment control (DYC) during acceleration and deceleration while turning. A previously reported method [1], which formulates the cornering resistance in steady-state cornering, was extended to so-called quasi steady-state cornering that includes acceleration and deceleration while turning. Simulations revealed that the direct yaw moment reduces the dissipation power due to the load shift between the front and rear wheels. In addition, the optimum direct yaw moment cancels out the understeer augmented by acceleration. In contrast, anti-direct yaw moment optimizes the dissipation power during decelerating to maximize kinetic energy recovery. The optimization method proved that the optimum direct yaw moment can be achieved by equalizing the slip vectors of all the wheels.

Improvement of vehicle dynamics in limit cornering have been studied. Simulations and tests have verified that vehicle stability and course trace performance in limit cornering have been improved by active brake control of each wheel. The controler manages vehicle yaw moment utilizing difference braking force between left and right wheels, and vehicle deceleration utilizing sum of braking forces of all wheels.

Active control systems pertaining to handling and stability have been systematically analyzed and tested. While the tires maintain adhesion the most effective system is steer angle control. A new 4WS strategy utilizing steering wheel angle feedforward and yaw velocity feedback functions is found to minimize the effect of external disturbances as well as to optimize steering response. When the limits of tire adhesion are approached other control systems must be adopted. Experimental methods of controlling the distribution of the driving/braking force and roll stiffness, based upon yaw velocity model following strategy, indicate a high potential for improving cornering performance.