Research On Control Strategy Of AC Servo System Based On Fractional Order PI~?

AC servo system is widely used in industry because of its high precision and good performance.However,with the rapid development of industrial automation,the requirement of AC servo system control performance is increasing.The PID controller is still the common control method of AC servo system,although its structure is simple and easy to realize,the robustness is not ideal when the system parameters change and external disturbances exist.In recent years,due to the rapid development of fractional calculus theory,the fractional order controller has been extensively studied,and it shows better performance than the conventional PID controller.In order to improve the control performance of AC servo system,the application of the fractional order controller in AC servo system is studied in this paper.Firstly,this paper introduces the fractional control theory and the mathematical model of permanent magnet synchronous motor,The principle of vector control of permanent magnet synchronous motor AC servo system is discussed.The design method of current loop PI controller,velocity loop PI controller and the fractional order PI?controller of servo system is analyzed.The space vector pulse width modulation technique is studied.On this basis,the simulation model of permanent magnet synchronous motor AC servo system is built.The results show that the fractional order PI?controller can effectively improve the anti-jamming ability of the servo system by simulating the servo system using the integer order PI controller and the fractional order PI? controller respectively.Secondly,aiming at the problem that the fractional order PI?controller of the servo system has more parameters and is difficult to be adjusted,a parameter optimization method based on differential evolution algorithm is designed.Due to the lack of standard differential evolution algorithm,the algorithm is improved by changing the selection method of the initial evolutionary population and designing the dynamic adjustment strategy for the variation factor and the crossover probability.The correctness of the improved algorithm is verified by the test function.Then,the improved algorithm is applied to the parametric optimization of the fractional order PI? controller of AC servo system.The simulation results show that the improved algorithm can quickly search theideal controller parameter value of the servo system and realize the off-line setting of the controller parameters.Finally,a fractional order PI? controller based on RBF neural network is designed for AC servo system.RBF neural network was used to provide Jacobain information for fractional order PI? to set control parameters in this controller.This controller made a good use of model information and avoided uncertainty of manual tuning,on addition it also benefited from flexibility and robustness of fractional order PI?controller.The simulation results show that the proposed RBF neural network fractional order PI?controller can improve the control performance of servo system.