Fuzzy Discrete Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors(PMSMs) has been widely used in the field of high-performance AC servo system because of its considerable advantages such as simple construction, low maintenance and manufacturing cost and long life. From the perspective of control theory, PMSMs are usually multivariable and highly coupled and they are very sensitive to external load disturbances and parameter variations. Therefore, the studies of advanced control methods to control the PMSMs to get the perfect dynamic and static performance are of important theoretical and practical significance.The advent of digital technology and its widespread use have revolutionized the computer-based implementation of advanced control schemes. In fact, recent advances in digital microprocessor technology have given considerable credit to discrete-time control systems, exhibiting relatively low operational cost and flexibility in implementation. This has motivated an interesting research activity in the area of discrete-time control and has determined the development of discrete-time control methods. In order to achieve high performance of PMSMs, many researchers have aimed to develop nonlinear control methods for the PMSMs and various algorithms have been proposed including nonlinear feedback linearization control, sliding mode control and adaptive backstepping control. However, most of those methods above were developed for nonlinear continuous-time systems, namely, nonlinear discrete-time control design techniques for PMSMs drive system have not been discussed to the same degree.Motivated by the above facts, a discrete-time adaptive control for interior permanent magnet synchronous motors(IPMSMs) with d qL ?L(dL and qL are the d? q axis stator inductance of the IPMSM) is proposed based on fuzzy-approximation. The main contributions of this paper are that:1. According to the continuous-time IPMSM system model, an accurate approximate discrete-time IPMSM system model is derived by direct discretization using the Euler method.2. According to the discrete-time IPMSM system model, a speed tracking controller and a position tracking controller for IPMSM drive system are proposed via backstepping technique, which solves the “noncausal problem” in the discrete-time backsteeping design procedure via recursive method. Fuzzy logic systems are used to approximate the nonlinearities of the discrete-time IPMSM drive system which overcome the “coupling nonlinearity” and parameter variations.3. The Lyapunov theory is employed to analyze the stability of the discrete-time IPMSM control system. The proposed controllers can guarantee the good and tracking performance and robustness against the parameter uncertainties and load torque disturbance.4. The simulation of the proposed speed tracking controller and position tracking controller for IPMSM drive system are conducted via Matlab 7. Simulation results illustrate the effectiveness of the proposed control method.