On Discrete-time Sliding Mode Control Of PMSM AC Servo System Based On Disturbance Estimation

Permanent Magnet Synchronous Motor (PMSM) owns the advantages of high magnet density, small torque pulse, big torque-inertia ratio, high efficiency, simple structure and so on. PMSM has been applied to occasions that require high control precision and high reliability widely. PMSM AC servo system is a sort of advanced control system, whose output can respond to the input rapidly and accurately, but parameter uncertainty and load disturbance can influence the performance of high speed and high accuracy of PMSM AC servo system.Sliding mode control is insensitive to system perturbations and external disturbances, has the advantages of good robustness, and can be realized easily. Accordingly, it's hopeful to design a control strategy of high quality by adopting sliding mode control (SMC) to PMSM AC servo system. Due to the fast development of computer technology and DSP technology, computers have been applied widely in control fields. Discrete-time sliding mode control theory is worthy of being studied from both theory and application point of view Thus, this thesis mainly researches discrete-time sliding mode control based on disturbance estimation.Firstly, based on the analysis on the mathematical model of PMSM, this thesis gives the linear decoupling state equation of PMSM in the d-q coordinates by combining with Vector Control technique. Secondly, general discrete-time sliding mode controller is designed for system with matched disturbance, and it is applied to position tracking control of PMSM AC servo system. Simulation results show that this means can track reference value, and it has good robustness, but system exists some steady state error. Thirdly, discrete-time sliding mode controller based disturbance estimation is designed for system with matched disturbance. This controller can estimate the disturbance dynamics, and improve stable accuracy. This method is applied to position tracking control of PMSM AC servo system, and it can also estimate the change of load torque for PMSM AC servo system dynamics. Simulations show that discrete-time sliding mode controller based disturbance estimation can track reference value better and lower system steady state error so as to achieve position tracking accurately. At last, the conclusions are drawn, and the further research directions are presented.