Skyhook control using a full-vehicle model and four Relative Displacement Sensors

In this paper, a modified skyhook control of the semi-active suspension system equipped with an MR damper is investigated. In contrast to the conventional method, which uses two acceleration sensors on the sprung and unsprung masses, the use of four relative displacement sensors between the sprung and unsprung mass is assumed. Since the implementation of the skyhook control requires the knowledge on the absolute velocity of the sprung mass, three schemes for its estimation are proposed: the equations of motion approach, low-pass filter approach and low and high-pass filter approach. Through simulations, the use of the low and high-pass filter approach is suggested. The performance of the proposed modified skyhook control is compared with the conventional one, since the use of relative displacement sensors, rather than acceleration sensors, is a new direction for the advanced suspension system, the techniques developed in this paper will provide a viable solution to that direction.