Research On Control Strategy For PMSM AC Servo System

High-level manufacturing industry is one of the six emerging strategic industries of "Twelfth National Five-Year Plan", which has the many advanced characters, including intensive technology and knowledge, high added value, good growth, etc. Servo system is an important driving source of modern manufacturing, and it is a trend that permanent magnet synchronous motor(PMSM) replaces the stepper motor and DC motor to become the main actuator of servo system. As PMSM servo system is vulnerable to motor parameters and external load disturbance, advanced control strategies should be studied to achieve strong anti-interference ability and adaptability. In view of the great practical significance and practical value of AC servo system, control technology for PMSM servo system is studied and a PMSM servo controller is designed in this paper.Firstly, the mathematical model for PMSM is established under three types of coordinate. On that basis, different speed-control strategies for PMSM are analysed, and the vector control algorithms with different current control objective are compared. Ultimately, basic control strategy for PMSM servo control is determined. Three-loops design of the servo system is accomplished by an inside-outside design method. Simulation results show that the design is reasonable.Secondly, to solve the existing problems for inner two-loops design of servo system and meet the performance requirements of servo system, more advanced control strategies for PMSM servo system are discussed. Based on the differential negative feedback control strategy, a filter set two-degree-of-freedom control method is finally used in the speed loop, which achieves excellent performances in both tracking and disturbance rejecting.Thirdly, to achieve fast and accurate response, a feed-forward control strategy is used in the position loop, which can eliminate the error caused by the tracking lag. An identification method for the moment of inertia is designed. On that basis, an adaptive inertia control method of position loop is proposed.Finally, to ensure the accuracy of the three loops design of servo systems, a measurement method for PMSM parameters is studied. An experimental platform of PMSM servo system is built based on the tricore MCU TC1166, realizing the digital design of servo control strategy. The experimental results demonstrate the system has good dynamic performance and steady state accuracy, and the proposed control strategy is reasonable and feasible.