Study On The Dynamic Response Of Automotive Magnetorheological Dampers

Due to its good controllability, wide dynamic range, fast response, low powerrequirement and comparatively simple structure, magnetorheological (MR) dampers hasbecome one of the focus research projects in automotive semi-active suspension.Besides damping force and dynamic range, the dynamic response is another importantparameter of MR dampers, which is a key part of automotive MR semi-activesuspension system. The dynamic response is valuable because it is one of the criticalfactors that determine the practical effectiveness of automotive MR dampers, theapplications range of MR dampers and the controlling period directly. In this thesis, thedynamic response of automotive MR dampers is investigated and the effects of variousconditions are considered. The main contributions include the following:(1) The properties and applications of MR fluid is reviewed firstly, the importanceof the study on MR dampers dynamic response is discussed, and the present situationand existing problems of the study are summarized. Based on the present problems ofthe study, the main work is put forward.(2) Based on the hydrodynamics theory and working modes of MR dampers,applying the constitutive equations of Newton and Bingham fluid respectively, theparallel plates and annular duct based rheological equations are derived, the calculationapproach of damping force is gained, and the theoretical relation between appliedcurrent, piston velocity and damping force is determined, which establishes thetheoretical basis for the research of MR dampers dynamic response, propose of testapproach and design of test system. Based on theoretical analysis of damping force, thecalculation model of MR dampers dynamic response is built by analyzing the unstablestate of MR fluid between parallel plates. Furthermore, driving by current source, theeffect of the connecting way (parallel or serial) of electromagnetic coils is analyzedtheoretically.(3) According to the damping force function and practical condition of dampers, anexperimental approach for finding the dynamic response of automotive MR dampersand corresponding data processing are offered, the corresponding test system isdeveloped, including some important parts of the test system, such as current driverbased on PWM method, and its output characteristic and dynamic response areinvestigated theoretically and experimentally.(4) According to the time history of damping force, the computing method ofresponse time is determined. Based on the test system and the computing method, thedynamic response is investigated on the automotive MR dampers developed by Centerfor Intelligent Structures of Chongqing University under various conditions. Theparameters in consideration include connecting ways of electromagnetic coils, stepcurrent applied, piston velocity and operating temperature.