Research On Vehicle Seat Semi-Active Vibration Isolation System With Variable Stiffness And Damping Based On Magnetorheology

With the development of the automobile industry at home and aboard, the vehicle is no longer a simple transportation tool. People pay more attention to its comfortableness in addition to its driving performance. In order to reduce the vibration transmission to the human body and improve the comfort of the vehicle, a new semi-active seat suspension is built, which is based on magnetorheological dampers (MRD) and traditional semi-active suspension.First of all, the rheological mechanism of MR fluid(MRF) was analyzed. Secondly, MRD inverse model was established after comparing several different mechanical models of MRD and finding the hysteresis characteristics of MRD is found. Meanwhile, the original Bouc-Wen phenomenon model and a double Sigmoid and general hysteresis model were simplified. Basing on the MRD, a new semi-active seat suspension using two controllable dampers and two constant springs is built. Then, a suitable body model is chosen for the seat suspension after building a new seat suspension and determining dampers working mode and mechanical model. It is an integrated body-seat suspension. The mathematical model of this whole model was set up by using Newton’s law and state space equation.This semi-active body-seat suspension used on-off control algorithm which is similar with the classic sky-hook control. On-off control strategy can make each dampers has two extreme values. Using this control policy the control system can have seven different conditions. The random road excitation in time domain was used to the vibration isolation simulation on the Matlab/Simulink simulation software platform. It can be seen that both the peak value of acceleration and the mean square root value of the semi-active suspension are less than those of passive suspension. At the same time, the vibration isolation effect of the new suspension with on-off control is better than the traditional semi-active suspension which is much better than passive suspension.Furthermore, a quasi-active control which is based on the active control theory was proposed. The quasi-active controller is designed using the principle that the resultant force of the system is equal to zero. This controller can regulate the input current of the MRD so that the force of dampers can be controlled. The resultant force contains elastic force and damping force on the seat is zero. The simulation result shows that quasi-active control is inferior to the on-off control.Finally, bench test for the semi-active seat suspension vibration isolation was performed. Ignoring the error in the experiment, the performance of vibration control of the semi-active suspension is superior to passive suspension, which proves that he semi-active seat suspension with variable stiffness and damping is feasible.