Research On The Identification Of PMSM’s Speed Without Sensors Based On The Sliding-Mode Observer

Compared to conventional AC motors, permanent magnet synchronous motors have unique advantages, such as more simple and reliable structure, larger energy density and lower loss. They are more and more being used in the common servo systems, not just in the aerospace, robots and other high-tech fields. Vector control is a vitally important method to design a high-performance control system. PMSMs are more adaptable to be the object of the vector control system, due to the absence of the slip frequency. But, the signals of the speed and rotor position of the motor must be real-time detected as the feedback to guarantee the high performance of the system. Currently, the detection is usually finished by some special optical sensors. However, the employ of the sensors not only increases the cost, but also decreases the reliability of t he s ystem. S o, t o obt ain a r easonable a nd e ffective m ethod t o a chieve t he estimation about the motor status has become an important topic.The s liding m ode c ontrol is an important theory t o t he de sign of automatic control system for its feature of strong robustness. The sliding mode observer also has been a key solution to realize the identification of the motor status. The study in the paper is based on the terminal sliding mode, which has the advantage that makes the system converge to zeros in finite time. In order to simplify its system structure, the paper pr oposed an i mproved s liding-mode m ethod. T he ne w m ethod i nherits a nd absorbs the advantages of the terminal sliding-mode and has a simple structure. In the paper, firstly, the principle of the terminal sliding mode is analyzed. Then its merit and demerit is summarized reasonable. Secondly, the improved theory is proposed. Also, detailed analysis and complete deduction of the observer’s performance based on the new method is shown. Finally, the PMSM’s vector control system is realized in the Matlab/Simulink environment. Furthermore, the estimation system is added to the control system to test the proposed observer.According to analysis of the simulation, the proposed observer is effective to achieve the aim. It can follow the tracks of the actual speed of the motor accurately and has strong robustness to the external disturbance. The sensorless control system can work well without the speed sensor.