Research On MEMS Gyroscope Control With Nonlinear Input Using Sliding Mode Control Strategy

With the rapid development of the MEMS integrated design technology, MEMS gyroscopes have greatly become a kind of market potential angular velocity sensor. In various areas, especially in the automotive and electronic industry, it has been widly applied. However,considering the actual application, the physical limitations of this device, external environmental interference and other factors, input nonlinear effects (including sector,deadline, hysteresis, etc.) inevitably exist in control system, micrometer scale effect under the influence of micromechanical transducer is particularly complex. Various nonlinear effects impact the precision of the system, and it even results in severe instability. Therefore, it is necessary to suppress or compensate the input nonlinear effects, in order to obtain the desired control performance. This paper studies the sliding mode control with input nonlinear characteristics of MEMS gyroscope system. During the study of MEMS gyroscopes, this paper considers the existence of the sector, hysteresis and dead-zone status, and the corresponding sliding mode controller is proposed for specific research questions.Firstly, the researching situation and some basic knowledge about MEMS gyroscopes are introduced in this paper. In researching situation, the current problems of MEMS gyroscope system and common control design methods are analyzed. The self-excited oscillation control and PLL control technologies based on the defects of traditional operational mode are considered, which proves that it is necessary to use new operation mode. In the part of relating knowledge, the basic theories of MEMS gyroscopes and relative control methods are introduced in this paper, including Coriolis effects, dynamics equation under the traditional operation mode and mathematical model under the new operation mode. At the same time,several control methods are briefly introduced, including adaptive control strategy, sliding mode control strategy, backstepping control strategy and neural network control strategy.Secondly, I study the sliding mode control problem of gyro system with unknown sector boundary. Two adaptive controllers are designed for mode motion tracking of a MEMS triaxial gyroscope and zero adjustment of a Z-axis MEMS gyroscope according to the use of Lyapunov stability theory and LMI technology respectively. The nonsingular terminal sliding controller not only avoids the singular problem in conventional terminal sliding mode control,but also achieves the finite-time tracking of MEMS gyro mode motion.Thirdly, I investigate the hysteresis problem caused by MEMS gyroscope transducer in the working process. For example, in the Backlash-like hysteresis model, two sliding mode controllers are designed which are based on two control loops (displacement control loop and velocity control loop) and adaptive global backstepping control method,by sliding mode control to outside interference insensitivity to weaken the influence of the hysteresis characteristics of the control system,the simulations verify its validity of suppress the hysteresis input nonlinearity.Finally, for the MEMS gyroscopes with unknown and asymmetry dead-zone, neural network compensation controller is designed to limit its effects. The whole control process consists of two RBF neural networks, with cross-coupling existing between two neural networks. Finally, according to Lyapunov theory proved that both tracking error of closed-loop gyro system and neural network weight parameters have the global uniform ultimate bounded stability. Experimental simulation results verify that the controller can effectively compensate the dead-zone characteristic.