Investigation On Vibration Isolation System With Hysteretic Actuator

Vibration isolation control is an important research branch of vibration control,and is widely applied in many areas.Recently,with the higher requirement for isolation control specifications and introduction of novel actuators,researchers have already recognized the difficulty and challenge of the problems resulting from dynamic and nonlinear characteristic of actuators when design and synthetize the controller.Among nonlinearities,hysteresis is the most mathematically intractable one.The dissertation is partially supported by the National Natural Science Foundation of China(No.10472073, Dynamic behaviors control for systems embeded with controllable hysteretic elements) and the Natural Science Foundation of Hebei Province(No.E2005000507,Robust stability and dynamic behaviors control for vibration control systems with controllable hysteretic elements).Two vibration isolation systems with hysteretic actuator are taken as the research cases,one is the semi-active vibration isolation system with Magneto-rheological(MR) damper,the other is the active vibration isolation system with electromagnetic actuator.The focus of this dissertation is on the hysteresis of the actuator and the main contributions of this work are as follows:1.Experimental systems for testing the actuators are designed and set up.For MR damper,the tests have shown that,the damping force depends not only on the amplitude and frequency of the relative velocity,but also on the amplitude and frequency of the excitation current.For electromagnetic actuator,the practical static relationship between electromagnetic force and the related factors such as the excitation current,the air gap is not strictly in line with the theoretical mode.There exists significant rate-independent hysteresis between the electromagnetic force and the excitation current.The hysteresis between the electromagnetic force and the air gap is weak.2.On the basis of inquiring the relevant literatures and the experimental results,an electro-mechanical coupled model for MR damper is presented,which is based on a novel modeling idea considering a damper together with control device,and with electromagnetic rheological response and mechanical response separately denoted.An approximate smooth representation for Bingham model is investigated,with a sigmoid function as a substitution for the piece-wise function.For electromagnetic actuator,in order to demonstrate the hysteresis and easy to treat in following control issues,an undetermined description model is proposed.The model for bidirectional electromagnetic actuator is resulted from coupling the dynamic model of excition process with the electromagnetic forces hysteresis.3.Several semi-active(SA) switch policies for vibration isolation system with MR damper are investigated,and simulations to examine the effectiveness performed. Additionally,a time delay compensation method to weaken the adverse influence on the performance with basic switch policies is introduced,which is examined by simulation.4.Sliding mode control for active vibration isolation system with electromagnetic actuator is studied.In determing the sliding mode control law,two models for the bidirectional electromagnetic actuator are employed,one is the author proposed model, the other is the Bouc-Wen model.Simulations show that,short time excitation through the isolation system can be perfectly isolated with the proposed sliding mode control law,while for continuously excitation,the vibration cann't be fully suppressed.5.A SA isolation system with MR damper for experimental purpose is designed and fabricated.Performance.under the switch control policies and the effects resulting from the sampling rate are investigated.Experimentals show that,the performance of SA switch policies show significant advantage over that of the passive control near resonance,while,in the higher frequency range,the switch policies function poorer. Additionally,the smaller the sampling rate is,the poorer the isolation performance of the SA swich control.These qualitative trend conclusions are in accordance with what we got from simulations.