Research On Sliding Mode Control Of MEMS Electromagnetic Micromirror And Capacitive Micromachined Ultrasonic Transducer

MEMS as a new cross-disciplinary interest attracted a large number of research scholars since the eighties and nineties to the beginning of this century.Miniaturization,easy integration,low power consumption and mass production of MEMS make it widely used in many fields,such as national defense,aerospace,electronics,medical devices and so on.Due to its wide scanning range,low driving voltage,large deflection angle and some other characteristics,the electromagnetic micro mirror has been widely concerned by researchers.The same to CMUT,it has been widely concerned because of its advantages of high electromechanical conversion rate and high sound pressure.The application conditions of MEMS devices are becoming increasingly harsh with the development of microelectromechanical technology,and the improvement of the performance of microelectromechanical devices has become the most important research.The method of improving the performance of closed-loop MEMS is different from traditional methods based on process transformation,not only does it not change the original parameters of micro devices,but also improve their dynamic performance by means of controller design.In this study,we take micro capacitance ultrasonic sensors(CMUT)and electromagnetic micromirrors as our objective.Then we focus on the modeling analysis and the design and analysis of the controller.After that the experimental verification of the microelectromechanical system has been done.Specific research work and the main contributions include the following aspects: 1.According to the transfer process of MEMS electromagnetic micro mirror deflection energy,we use finite element analysis(FEM)and electromagnetic theory on MEMS electro-magnetic modeling analysis of micro mirror.Then A general model for non-uniform magnetic field is established.2.In order to achieve fast response and accurate switch characteristics in optical switch,varieties of closed-loop control algorithm is proposed to improve the performance of the MEMS torsional micromirror,such as PID control,the improved PID control,the sliding mode control and the second order integral sliding mode control.Through the comparison between simulation and experimental analysis,the system could overcome the chattering of micromirror effectively by using the second order integral sliding mode control for set point tracking control problem.It has important research value for optical switch based on electromagnetic MEMS torsional micromirror.3.Based on the MEMS electromagnetic micromirror experimental platform,a backstepping sliding mode control algorithm is proposed.The simulation and experimental results show that the backstepping sliding mode control algorithm meets the requirement of rapidity and effectiveness under the action of micromirror set point tracking control and sinusoidal signal dynamic tracking control.The tracking performace of sinusoidal signal also lays a solid foundation for the micromirror's the application of optical switch and bar code scanning.4.Based on the difference dimension between the top film and the cavity of the MEMS micro capacitance ultrasonic sensor,the top film is equivalent to the rigid plate,then the equivalent 1-D lumped CMUT model is established.Next we propose a sliding mode composite nonlinear control algorithm,which solves the pull-in problem of CMUT under the condition of input saturation effectively.Meanwhile,the controller makes the upper plate stable operation range reach 90% of the whole cavity.