Sensorless Control Of Permanent Magnet Synchronous Motor Base On Sliding-mode Observer

Permanent magnet synchronous motor (PMSM) has the characteristic of small size, simple structure, low energy consumption, high power density and maintenance-free, taking a vital position in alternating current governor system. Recently, the development of PMSM are closely linked to permanent magnet material, and with the rapid increasing of permanent magnet material in performance and high-performance PMSM, the PMSM are widely applied in many motion control systems. Previously, position sensors are assembled on electromotor axes to get the position and speed of rotors, so as to get high-performance speed control in PMSM control system, however, the mechanical sensors enlarge the size of motor, lower the feasibility and increase cost of system, of which inconvenience are resolved with the application of sensor-less control technology.Sensorless control technology get physical quantities such as current and voltage of motor to evaluate the position of rotor in special algorithm, collect the speed and position of permanent magnet rotor, and complete close-loop control. At present, Sliding mode variable structure control algorithm has become the hotspot of PMSM speed sensorless control research, which is a sort of discrete sliding mode variable structure control and the control strategy of system structure changes over time, that will cause system chattering. Traditional sliding mode observer estimates back EMF of the motor to obtain the position and speed of the motor with the sliding mode surface of current error of stator. The back EMF, however, is under the condition of low speed with small amplitude, high noise, which has serious impact on its application in low speed range.Based on permanent magnet synchronous motor as the research object, this paper first simply introduces the structure and mathematical model of permanent magnet synchronous motor, in detail elaborates the space vector pulse width modulation (SVPWM) technology theoretical basis, and select the vector of id=0control strategy to drive permanent magnet synchronous motor. The new sliding mode observer method is put forward, and switch function uses saturation function to replace it to minimize "chattering", and by using kalman filter that filters out the potential noise, raises the back emf estimation accuracy. Using MATLAB/Simulink software to establish a system simulation model, the simulation experiments with traditional and new observer strategy respectively, and the simulation results show that this paper proposed a new type of sliding mode observer control strategy which can effectively inhibit "chattering", make the whole system has good control performance and robustness.Finally the paper adopts a special motor control chip DSP (TMS320LF2812) of TI company as the core processing chip of control system, uses intelligent power module IPM as hardware of the power switch components of system development control system, and do software design for speed sensorless control strategy based on sliding mode observer. Results proved that the speed sensorless control strategy based on sliding mode observer, has good robustness, and the control algorithm is simple and easy engineering implementation, etc, and expand the application scope of speed sensorless method.