ACTIVE SUSPENSION OF TRUCK SEAT

The driver's seat of a heavy duty truck is usually mounted on a spring -damper assembly anchored to the cab floor. To improve riding comfort, this study investigated the effects of mounting a computer-controlled actuator in parallel with the traditional spring-damper assembly. A d ynamic model of the seat is represented by a two degree-of-freedom sys tem, including a cushion. In this paper, a control system is designed, using optimal control theory, which minimizes rms vertical accelerati on at a point representing the driver's hip point. In this system, acc elerations of the hip point, the seat frame and the cab floor are pick ed up and integrated to obtain the state variables to be fed back and fed forward to the actuator through a digital computer. The actuator i s constructed with electric servo-motor and ball-screw mechanism. The experimental study was carried out on a shaker, which simulates the vi brations of the cab Boor in actual service. Results were obtained for both a dummy and a real human body. The vibration test produced rms ac celerations of the seat and the hip point of about 1.0 m/s(2) without the actuator, while the rms accelerations were suppressed to about 0.5 m/s(2) at a rms input voltage to the servo-motor of 1.0 V.