Modeling and control of MR damper considering trapped air effect

Due to the high viscosity of magnetorheological(MR)fluid, eliminating air pockets dissolved in the fluid is very difficult, which results in a force lag phenomenon. In order to evaluate the performance of a semi-active control system based on the MR damper considering the trapped air effect, a performance test on a MR damper is carried out under different loading cases, and the influence of the input current, excitation amplitude and frequency on the force lag phenomenon is analyzed. A concise and efficient parametric model, combining the simple Bouc-Wen model and a spring with small stiffness, is proposed to portray the experimental characteristics of the MR damper with force lag, and then the response analysis of the semi-active controlled single-degree-of-freedom(SDOF)structure is performed using the classic clipped-optimal control strategy based on acceleration feedback. Numerical results show that the trapped air in the MR fluid can weaken the control effect of the MR damper, and the performance of the semi-active control system will be reduced more obviously and become close to the passive-off control with the increasing content of air trapped in the MR fluid.