Study Of Properties And Vibration Control Method Of MR Damper

Magnetorheological (MR) damper，possessing many unmatched and distinguished properties such asthe adjustability of control system and the stability of passive control system, is a fine semi-active controldevice. It is of great application value to the following vibration control fields: mechanism, automobile,aerospace, bridge construction etc. The mechanical properties, response time and control methods of MRdamper have an important influence on vibration reduction of MR damper, so it is very significant to studythese factors in order to promote the application in engineering. Therefore, this paper, taking MR damperswhich are used in vibration absorption of the stay-cables as research object, is carried out as follows.First of all, this paper analyzes the mechanism of response time through MR fluid, the flexibility ofmechanism, control electric circuit and magnetic circuit, and experimentally studies the response time ofMR damper with the changing of electric current and velocity. And the optimized twist method of magneticcoils is put forward on the basis of the analyses of magnetic induction strength of damping clearances andthe ratio of the inductor to the resistor. The study shows that the twist method of two magnetic coilsconnected in subtractive series can not only effectively improve the damping force and adjusting coefficientof MR damper but also decrease the response time of MR damper.Secondly, structural parameters of MR damper are optimized and a new MR damper is designed andmanufactured. The improvements of the new MR damper in structure can be shown as follows: addingpermanent magnets to piston to increase original damping force and reduce the cohesion and sedimentationof MR; connecting magnetic coils in subtractive series to decrease the response time and improve dampingforce and adjusting coefficient; adopting multi-stage seal to improve the tightness.Thirdly, the damping force and response time of the new MR damper are tested. On the basis ofexperiments, the relationship between damping force and three factors namely displacement, electriccurrent and the piston velocity is analyzed, and the tendencies of the response time of new MR damper withthe changing of electric current and piston velocity are studied. After comparing with the original damper,we find that under the same experimental conditions damping force of the new MR damper can increase by12%at least and response time can decrease by50%at most.Finally, a damping control algorithm based on BP neural network PID is designed to make a bettercontrol of the vibration of the stay-cable using MR damper. This algorithm, taking advantage of the on-linestudy ability of BP neural network, can adjust and optimize the parameters of PID constantly, which makesthe vibration control of the stay-cable and MR damper system have very strong self-adaptive capacity androbustness.