A New Model and an Optimal Pole-Placement Control of the Macpherson Suspension System

In this paper a new model and an optimal pole-placement control for the Macpherson suspension system are investigated. The focus in this new modeling is the rotational motion of the unsprung mass. The two generalized coordinates selected in this new model are the vertical displacement of the sprung mass and the angular displacement of the control arm. The vertical acceleration of the sprung mass is measured, while the angular displacement of the control arm is estimated. It is shown that the conventional model is a special case of this new model since the transfer function of this new model coincides with that of the conventional one if the lower support point of the damper is located at the mass center of the unsprung mass. It is also shown that the resonance frequencies of this new model agree better with the experimental results. Therefore, this new model is more general in the sense that it provides an extra degree of freedom in determining a plant model for control system design. An optimal pole-placement control which combines the LQ control and the pole-placement technique is investigated using this new model. The control law derived for an active suspension system is applied to the system with a semi-active damper, and the performance degradation with a semi-active actuator is evaluated. Simulations are provided.