Sliding Mode Observer Based Vector Control For Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor (PMSM) because of its small size, simple structure high efficiency, reliable operation, easy maintenance etc., has been widely used in industrial and civilian application. In order to obtain accurate information of rotor position and speed to achieve high-performance closed-loop control of PMSM, the mechanical sensors are needed to be installed on the rotor. The installation of sensors not only increases the electrical costs, but also increases the complexity of the system and reduces the system reliability, all of that on some extent, limiting the applicative promotion of PMSM. Therefore, research on PMSM control technology without speed sensor is necessary. Based on the comparison of various speed estimation methods. Sliding Mode Variable Structure Theory to be adopted to estimate the rotor position and speed of PMSM in this paper.Paper first introduces the development status of PMSM control, several motor control strategies are introduced, and focus on several sensorless control methods do a comparative analysis. Subsequently, establishes the mathematical model of the PMSM under different coordinate systems. Later, studies the basic principles of motor vector control, and focuses on the space vector pulse width modulation principle algorithms. In order to get the best control performance, this paper adopted the vector control strategies of id=0for PMSM.Researches on the Sliding Mode Variable Structure Theory, realizes the rotor position and speed estimating based on sliding mode observer. In depth analysis of the problem exist in traditional sliding mode observer, for example chattering, phase delay caused by the low pass filter, estimating imprecise, etc. Then, proposes several improvement measures to solve these problems. Using saturation function instead of switching function to weaken chattering; Building EMF observer based on the mathematical model of two-phase stationary coordinate system, to get a more accurate estimating of the EMF for a more accurate rotor position and speed calculate; for the setting of the cutoff frequency and the coefficients in sliding mode observer and EMF observer, relates them to the rotor speed, to obtain a better estimating performance. Then, builds a PMSM vector control simulation system in MATLAB/simulink, makes simulation analysis for both the traditional sliding mode observer and the improved observer, the simulation results verify that the improved observer is effective.After a theoretical and simulation analysis, experiments have been done to testify and verify the feasibility of the strategy. Both sensor and sensorless control program based on DSP for PMSM are written in C language. In order to watch the motor experimental waveforms in real time, a monitor program is designed in LabVIEW8.6. Experimental analysis under the condition of constant speed, speed step, load disturbance has been done for the two algorithms. Comparing the experiment results, it shows that the proposed strategy can estimate rotor position and speed effectively, has certain practical value in practice application.