Research On PMSM Servo System Based On LADRC

Permanent Magnet synchronous Motor(PMSM)with its high power density,high torque/inertia ratio,high efficiency and easy maintenance etc,in the aerospace,radar,such as NC machine tools and robots servo applications has been widely used.The traditional PMSM servo system selects PI controller.As the PMSM itself is a multi-variable,strongly coupled,non-linear control object,and the traditional PI controller is difficult to meet the high performance requirements of the servo system.For this purpose,this paper studies the application of linear active disturbance rejection controller(LADRC)in PMSM servo system.(1)In order to improve the ability of disturbance rejection and noise suppression of the permanent magnet synchronous motor(PMSM)speed regulation system,three kinds of LADRC are designed for the PMSM speed regulation system,such as the traditional LADRC(TLADRC),the high-order LADRC(HLADRC)and the reduced-order LADRC(RLADRC).The differences among the proposed LADRC are the LESO,such as the traditional linear extended observer(TLESO),the high-order LESO(HLESO)and the reduced-order LESO(RLESO).The stability of the speed loop controlled by the three LADRC are demonstrated by employing the superposition principle,and the convergence conditions of the proposed LESO were analyzed at the same time.The frequency domain analysis of the various LESO was researched and the ability of disturbance rejection and noise suppression of the PMSM speed control system were compared combining with the speed response curve controlled by the various LADRC.The obtained conclusion can provide powerful support for selecting LESO in LADRC,and provide a theoretical basis for optimal design of PMSM speed control system.(2)The design of traditional position servo system is mainly realized by cascaded control,from the inner to the outer are the current loop,the speed loop and the position loop.However,this requires three sensors measuring the current,speed and position respectively,and the increasing of the sensors not only raising the economic costs,but also introducing more noise.Although the speed sensor is not needed,the speed can be calculated from the difference of position,but it can bring up the corresponding problem:because the location is lagging speed 90°,through the difference of location will bring phase lag;The difference amplifies the sensor noise.To this end,this chapter puts forward the integrated design scheme of the position servo system,which is to retain the current loop,and the speed loop and position are regarded as a second order system,and the design of the third-order LADRC is carried out.In order to realize the digital control,the discrete design of the zero-order preserving sampling method for LADRC is implemented.In addition,this chapter also analyzes the error caused by the tracking time varying signal of the position servo system,and proposes to solve the problem by adding differential feedforward.(3)In order to inhabit the PMSM servo system with flexible load of mechanical resonance,two kinds of motor speed feedback LADRC were designed,namely LADRC1 and LADRC2.Through the study of the mathematical model of two kinds of LADRC,the two degree of freedom form of the LADRC closed-loop control was derived,on this basis,the disturbance and noise transfer function of the impact on the system output have been obtained respectively,and the frequency domain analysis was carried out,and then the time domain analysis of the two LADRC control systems is compared,and the simulation analysis of the time domain verifies the conclusion of the frequency domain analysis.The results of this chapter provide the theoretical basis for selecting controller of the PMSM with flexible load servo system.