Studies On Several Control Problems Of Permanent Magnet AC Servo System

Because of the advantages of simple mechanical structure,high power density,stable torque and high reliability,permanent magnet synchronous motor(PMSM)has gradually become the first choice in the field of small and medium power level high-performance AC servo motor.The high performance PMSM servo system needs to have the control quality of fast response,precise positioning and strong anti-interference ability.At present,there are two problems to be solved in PMSM servo control system,one is the dynamic response and robustness of servo system under nonlinear factors and uncertainty disturbance,the other is the mechanical resonance of servo system caused by non rigid load connection equipment.Therefore,in this paper,based on the demand and practical experience of PMSM servo control system,taking PMSM as the research object,the related problems of its control system are studied.The main work includes:1)This paper analyzes the structure of permanent magnet AC servo system,establishes the mathematical model of permanent magnet synchronous motor,and analyzes the vector control method of permanent magnet AC servo system through decoupling control and coordinate transformation,current controller,speed controller and position controller design.Through the discussion of the permanent magnet AC servo system,the foundation is laid for the following research of some control problems of the permanent magnet AC servo system.2)This paper introduces the advantages of auto disturbance rejection controller(ADRC)and the standard ADRC model,applies ADRC to the current loop of permanent magnet AC servo control system,designs the ADRC composed of linear extended state observer and state error feedback rate,and then analyzes the performance of the current loop added to the controller.Finally,the anti-interference performance of the current loop is analyzed.3)Carry out the design of speed loop compound PI controller and analyze its performance,at the same time,the output differential negative feedback and IP controller are selected according to the method of restraining overshoot,and the variable structure PI controller is further designed.Finally,the optimal PI controller and the variable gain PI controller are obtained.Through the design of compound PI controller of speed loop,the tracking performance of the system for continuous change input is improved.4)The mechanical resonance of the permanent magnet AC servo system is analyzed,and the main factors that affect the resonance are obtained.Further,the frequency of the resonance system is identified on-line by the fast Fourier transform,and finally the resonance frequency of the system is filtered by the notch filter.The influence of notch filter on the system is analyzed and the parameters of the filter are determined.Finally,the digital notch filter is realized.5)A servo system experiment platform based on PMSM is built.The experimental results of the current loop,speed loop and vibration control algorithm of the servo system proposed in this paper are described.The experimental results will verify the effectiveness and practicability of the current loop,speed loop and vibration control algorithm proposed in this paper.The research of this paper improves the control method of the permanent magnet AC servo control system,which has certain guiding significance and reference value for the design of the servo control system in the actual project.