Research On Key Issuses Of Permanent Magnet Sysnchronous Motor Sliding Mode Speed Control System

Permanent magnet synchronous motor (PMSM) has been widely used in many areas, such as numerical control machine tool industry, aerospace and robotics research, because of its simple structure, small size, high efficiency and reliable operation. PMSM control system is a typical strong coupling, multivariable and nonlinear system, in which many uncertainty problems including parameters perturbation and external disturbance need to be sloved to meet control requirements of high reliability and high performance. Therefore, research on sliding mode control strategies of PMSM, sensorless control method and fault diagnostics technology of inverters in motor drive systems has great significance in theory and applicationFirstly, PMSM model is built. Then in order to improve the performance of the PMSM control system, the motor control strategies based on sliding-mode reaching law are studied in this paper. Based on the chattering analysis of traditional equal reaching law and traditional exponential reaching law, two types of noval sliding-mode reaching law are proposed. The novel sliding-mode reaching law not noly can suppress the chartering but aslo promote the convergence speed of the sliding-mode surface. The PMSM sliding-mode speed control system is built using proposed reaching law, and then the sliding-mode speed controller and sliding-mode current controller are designed.Secondly, based on impact analysis of disturbance in PMSM systems, an extended sliding-mode disturbance observer is proposed to estimate lumped uncertainties directly, to compensate strong disturbances and achieve high servo precisions. The proposed disturbance observer considers speed error as sliding-mode surface, which can estimate the disturbance exactly and quickly with low chattering. Then, to further improve the disturbance rejection performance of motor system, the estimated system disturbance is considered as the feedforward compensation part to compensate sliding-mode speed controller. Thus, a composite control method combining a sliding-mode controller part and a feedforward compensation part based on disturbance observer is developed. Simulation and experimental results show that the composite control method can improve disturbance rejection ability of PMSM systems.In order to enhance environment adaptability and reliability of PMSM control systems, based on traditional sliding-mode position and speed observer in PMSM control system, a second-order hybrid terminal sliding-mode position and speed observer is proposed. The chartering is suppressed and low pass filter used in traditional sliding-mode observer is avoided in the proposed observer. Meanwhile, effects of the parameters perturbation in PMSM on estimated position and speed are analysed. Simulation and experimental results show that second-order hybrid terminal sliding-mode observer can estimate position and speed of PMSM exactly, and improve estimate precision.Finally, in order to further improve the reliability of motor control system, a novel diagnostic method for open-switch faults in inverters using second-order sliding-mode voltage observer and Mixed Logical Dynamical (MLD) model is proposed. The presented method is achieved by analysis of MLD model of the voltage source inverter under both healthy and faulty conditions. Due to the different phase voltage values of the machine under healthy condition from open switch faults, the residuals of phase voltage can be used to detect the faults and identified the faulty switch of the voltage source inverter. Finally, simulation and experimental results show the validity of the proposed diagnostic approach.