A Model Based Approach for Design of Semiactive Suspension Using Variable Structure Control

This paper presents the modeling and simulation of a magnetorheological damper based semiactive suspension using variable structure controllers. Passive suspension systems tend to limit the trade-off between passenger comfort and road handling. But Semiactive suspensions can reduce this trade-off margin and dynamically respond to the damping requirements. Active suspensions provide the best response since they can add damping force in any direction, but are prone to higher power consumption. Semiactive suspensions just change the damping coefficient by simply applying a control voltage as and when required. The performance of three controllerssigma 1, sigma 2 and sigma 3, are measured and analyzed using nine parameters using peak, root mean square and normalized approaches. The road excitations considered are a single road hump and random road disturbance. The control system is applied to a 2-degree of freedom quarter car model of a passenger car. A modified BoucWen model of MR damper is used to cater to the system responses at near zero velocities. The performance of these controllers is superior to the uncontrolled case, which is similar to passive suspension system. Sigma 3 controller is superior to the uncontrolled system by 63% while sigma 1 and sigma 2 are superior by 53% when it comes to peak suspension deflection for a random road disturbance. Both sigma 2 and sigma 3 controllers are better in terms of performance. The validation of the semiactive suspension leads to selection of sigma 2 controller over sigma 3 controller because of its simplicity in implementation in real-time systems. Key Words— Semiactive suspension, magnetorheological damper, variable structure controller, quarter car model.