Research On Fault Diagnosis Of Electromagnetic Micromirror Based On Unscented Kalman Filter

MEMS（Micro Electromechanical System）belongs to Micro-Optical Electromechanical Systems.For its small size,low power consumption,high precision,fast response and many other advantages,it has a wide range of applications in optical communication,biochemistry,medical imaging and consumer electronics.However,the micromirror system exists irreversible failure in applications,which seriously affects the life cycle of related products.Therefore,it is of great practical significance to research the fault mode and diagnosis method of MEMS electromagnetic micromirror,predict its life cycle,and replace relevant parts in advance.MEMS electromagnetic micromirror is chosen as the research object,considering process noise and measurement noise in application,a suitable model is established based on analysis and research of the system.Based on the established model,the state estimation and fault diagnosis of the system are realized through filtering.The main research work is listed as follows:（1）Through analyzing experimental data,a nonlinear hysteresis exists in the electromagnetic micromirror system.based on the idea of block modeling,a Hammerstein model with hysteresis is used to describe the electromagnetic micromirror system,and its corresponding unknown parameters are identified.For the convenience of filter design,the Duhem model is used to describe the hysteresis in the system model.In addition,and the complete state space expression of the electromagnetic micromirror system is written,and it is convenient to subsequent filter design and fault diagnosis research later.Simulation and experimental results show the validation the system model.（2）In Hammerstein model with hysteresis,the intermediate variable,namely,output of hysteresis cannot be measured,directly,so it is difficult to realize state estimation of the whole system.Thus,an unscented Kalman filter for the micromirror system is constructed to achieve the state estimation of the system.By comparing with the traditional Kalman filter by experimental results,it shows that the unscented Kalman filter constructed can better follow the system state.（3）Based on the previously constructed unscented Kalman filter,the fault diagnosis module of electromagnetic micromirror system is designed.By analyzing experimental data,the faults of experimental electromagnetic micromirrors are classified into rotating shaft fracture,material fatigue and electromagnetic coil fault.For different fault model modes,the time-frequency characteristics of the output signal of the fault diagnosis module are analyzed.The time-frequency characteristics and mean square error are compared with their corresponding values of the normal operation to determine the fault type.The experimental results show that the fault diagnosis module designed can judge different faults of micromirror and meet the design requirements.