Position Sensorless Control For Permanent Magnet Synchronous Motor Using Sliding Mode Observer

The permanent magnet synchronous motor (PMSM) is a superiority-performanceand widely-used motor. The PMSM speed regulator system adopted VVVF strategy tocontrol the PMSM. It has many merits such as low-dynamic, high-reliability andprecise-control, so it is widely used in many regions. However, when the PMSMwhose rotor without damping windings operated in open loop, the system is not stable,the electric efficiency decreased and the rotor temperature increased, the NFeBpermanent magnet demagnetized, sometimes the motor lost synchronism, the positionand speed precise control of PMSM system build in the speed closed-loop control, sohow to acquire rotor position and speed signal is a most important strategy in thewhole system. At present, in mostly regulation drive systems, the mostly method is toinstall a position sensor in the rotor shaft. But the sensors increase the cost anddecrease the reliability. In these backgrounds, there has been an increased interest indeveloping techniques to obtain the position and speed information for the PMSMwithout external position sensors. Position sensorless control for PMSMs will bewidely used in some special or low-precision situation.We can measure themeasurable physical quantity such as threehase current, voltage etc to estimate theposition and speed through special observer strategy.This paper introduced the structure and mathematic model of PMSM, expatiate thetheoretical basis of spacial vector pulse width modulation (SVPWM) and the wavegeneration, and did some research in closed-loop control strategy. Because ofsuperiority performance and abundant external devices of the TMS320LF2407 controlchip, we use this kind chip to design the hardware and software system, so we cancontrol the PMSM by this control system.This paper use Matlab to build.the emulation mathematic model of PMSM andconstruct the PMSM regulation system according to SVPWM theory. Themathematical model of PMSM in a stationary αβ reference frame is adopted, and thesystem is controlled according to the control theory of sliding mode observer. In orderto achieve closed loop operation of the motor, the stator magnetic field should bevertical with the rotor magnetic field and be synchronous with rotor rotating, so theposition θ and speed ω of PMSM is real-time estimated and the estimatedpositionθ is modified continuously. Theoretical analysis and simulation results showthat the proposed strategy has stronger robustness and satisfactory performance.