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Toyota has succeeded in developing for mass production the active four-wheel steering(4WS) system using yaw rate feedback and steering angle feedforward control. The active 4WS system consists of a group of various sensors, including the newly developed yaw rate sensor, ECU, a rear wheel steering actuator that employs a stepping motor and hydraulic valve, and other hydraulic elements, which actively control the steering angle of the rear wheels. The new system ensures a good response and a high level of stabililty for quick steering wen during a high-speed drive. When the vehicle deflects due to a sudden side wind, road surface disturbance, or abrupt braking, steering is automatically corrected through the rear wheels to significantly improve forward stability. In addition, the! system prwides improved performance in making small radius turns because the rear wheels are steering up to five degrees when the front wheels are turned to a large angle.

We have developed a new semi-active suspension, called Piezo TEMS, that uses piezoelectric ceramic for suspension control with sensor and actuator. It improves remarkably driveability with the firm damping force mode and enhances the ride comfort with the soft damping force mode immediately after the road surface input exceeding the threshold level.

TOYOTA has adopted the Active Hydropneumatic Suspension and the Active Four Wheel Steering(Active 4WS) for the 1991 SOARER. The SOARER'S Active Suspension. is based on CELICA'S Active Suspension for the 1989 mode1(1)(2)(3)(4)(5)(6)(7). Because the Suspension has no coil springs,improvements in both ride and handling performance are obtained. The Active 4WS controls the rear steering angle by using yaw rate feedback contro1,and this is the world's first system in massproduction car. TOYOTA has integrated the ABS and TRC to these systems in the SOARER. We have succeeded in improving the total vehicle dynamics performance,and have obtained higher maneuver-ability and controllability with a total integrated system. The following describes the effects of integrated control.