A Semiactive Vibration Control Design for Suspension Systems with Mr Dampers

In an automotive system, the vehicle suspension usually contributes to the vehicle's handling and braking for good active safety and driving pleasure and keeps the vehicle occupants comfortable and reasonably well isolated from road noise, bumps and vibrations. The design of vehicle suspension systems is an active research field in automotive industry (Du and Zhang, 2007; Guglielmino, et al., 2008). Most conventional suspensions use passive springs to absorb impacts and shock absorbers to control spring motions. The shock absorbers damp out the motions of a vehicle up and down on its springs, and also damp out much of the wheel bounce when the unsprung weight of a wheel, hub, axle and sometimes brakes and differential bounces up and down on the springiness of a tire. Semiactive suspension techniques (Karkoub and Dhabi, 2006; Shen, et al., 2006; Zapateiro, et al., 2009) promise a solution to the problem of vibration absorption with some comparatively better features than active and passive devices. Compared with passive dampers, active and semiactive devices can be tuned due to their flexible structure. One of the drawbacks of active dampers is that they may become unstable if the controller fails. On the contrary, semiactive devices are inherently stable, because they cannot inject energy to the controlled system, and will act as pure passive dampers in case of control failure. Among semiactive control devices, magnetorheological (MR) dampers are particularly interesting because of the high damping force they can produce with low energy requirements (being possible to operate with batteries), simple mechanical design and low production costs. The damping force of MR dampers is produced when the MR fluid inside the device changes its rheological properties in the presence of a magnetic field. In other words, by varying the magnitude of an external magnetic field, the MR fluid can reversibly go from a liquid state to a semisolid one or vice versa (Carlson, 1999). Despite the above advantages, MR dampers have a complex nonlinear behavior that makes modeling and control a challenging task. In general, MR dampers exhibit a hysteretic force velocity loop response whose shape depends on the magnitude of the magnetic field and other variables. Diverse MR damper models have been developed for describing the nonlinear dynamics and formulating the semiactive control laws (Dyke, et al., 1998; Zapateiro and Luo, 2007; Rodriguez, et al., 2009). Most of the MR damper’s models found in literature are the socalled phenomenological models which are based on the mechanical behavior of the device (Spencer, et al., 1997; Ikhouane and Rodellar, 2007).