IMECE2005-80646 A NEW MODEL FOR MACPHERSON SUSPENSION SYSTEM AND OBSERVATION OF RIDECHARACTERISTICS AND ITS OPTIMAL CONTROL

ABSTRACT In this paper a new model for the MacPherson suspension system and its optimal control are investigated. The focuses of the modeling were to add the rotational motion of the unsprung mass and considering physical characteristics of the spindle such as mass and inertia moment. The vertical acceleration of the sprung mass is measured, while the angular displacement of the control arm is estimated. According to this model the ride characteristics such as alterations of the camber angle, king-pin angle and track are displayed. This model is more general in the sense that it provides an extra degree of freedom in determining the plant model for control system design. Optimal control theory was employed to derive a control law for an active suspension system. The performance degradation with an active actuator is evaluated. Simulations are also provided. INTRODUCTION The performance of a suspension system is characterized by the ride quality, the drive stability or maneuverability, the size of the rattle space and the dynamic tire force. The prime purpose of adopting an active/semi-active suspension system is to improve the ride quality and the drive stability. To improve the ride quality, it is important to isolate the sprung mass from the road disturbances and to decrease the resonance peak of the sprung mass, near 1 Hz, which is known to be a sensitive frequency to human body. On the other hand, to improve the drive stability, it is important to keep the tire in contact with the road surface and therefore to decrease the resonant peak near 10 Hz, which is the resonant frequency of the unsprung mass. For a given suspension spring, the better isolation of the sprung mass from the road disturbances can be achieved with a sof