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This article presents vibration control of a semi-active quarter-car suspension system equipped with a magneto-rheological damper that provides the physical constraint of a damping force. In this study, model predictive control was designed to handle the constraints of control input (i.e. the limited damping force). The explicit solution of model predictive control was computed using multi-parametric programming to reduce the computational time for real-time implementation and then adopted in the semi-active suspension system. The control performance of model predictive control was compared with that of a clipped linear-quadratic optimal controller, where the damping force was bound using a standard saturation function. Two types of road conditions (bump and random excitation) were applied to the suspension system, and the vibration control performance was evaluated through both simulations and experiments.

This article presents the quantitative feedback theory (QFT) based multivariable controller for the vertical and the pitch angle motion of a half‐car suspension system. A coupled half‐car system with significant uncertainty, due to sprung masses variation, poses a challenging control problem. Multi‐input multi‐output (MIMO) QFT method is used for this purpose which involves converting the actual MIMO system into an equivalent single‐input single‐output (SISO) system so that the design problem is carried out using the SISO QFT principles. The proposed idea is centered on by converting the coupled MIMO system into a decoupled one using the dynamic decoupler where in controllers are designed independently based on the equivalent SISO system. The designed QFT‐based controllers with the decoupler use the semiactive suspension strategy (realized using the magnetorheological (MR) damper) to reduce the vibration of the half‐car suspension system (in vertical/pitch angular motion) and hence to increase the ride comfort and the vehicle road holding. The feedback cost is less in the proposed design than the sequential QFT design. In this study, the MR damper dynamics is captured by the first‐order model which is realistic, efficient, and simple form. Extensive comparative simulation studies are carried out to illustrate the effectiveness of the proposed design over the existing methods such as passive and skyhook control under different road excitation.

In this study, a new class of magnetorheological (MR) damper, which can realize desired damping force at both low and high speeds of vehicle suspension systems, is proposed and its salient characteristics are shown through computer simulations. Unlike conventional MR dampers, the proposed MR damper has a specific pole shape function and therefore the damping coefficient is changed by varying the effective area of the main orifice. In addition, by controlling the opening or closing the bypass orifice, the drastic change of the damping coefficient is realizable. After briefly describing the operating principle, a mathematical modeling is performed considering the pole shape function which is a key feature of the proposed MR damper. Then, the field-dependent damping force and piston velocity-dependent characteristics are presented followed by an example on how to achieve desired damping force characteristics by changing the damping coefficient and slope breaking point which represents the bilinear damping property.