Combined Active Disturbance Rejection Control Vector Resonant And Load Observer For PMSLM Current Harmonic Suppression

The way for traditional numerical control machine tools to realize linear feed motion is that rotary motor combined with synchronous belt or roller screw,but the intermediate links of such schemes will bring great errors,Permanent Magnet Synchronous Linear Motor(PMSLM)avoids these limitations by eliminating the need for intermediate drives,and because of its large stroke,high precision and other features,PMSLM is popular in high precision applications such as high-grade CNC machine and 3D printers.Three closed-loop control mode is the control mode used by most PMSLM servo control systems,in which the current loop is worked entirely in the servo drive,which is the basis of control,so,high-quality current output determines the quality of the whole control system.When the PMSLM is running;there are inevitably various disturbances in the control system,which will produce a lot of current harmonics and affect the control precision of servo system seriously.These disturbances can be divided into external disturbances and internal disturbances.The internal disturbance of the control system includes periodic disturbance and non-periodic disturbance.First of all,if the temperature of the linear motor increases with a long time running,the resistance parameters,inductance parameters and flux linkage parameters of the motor will change with the increase of temperature,the variation of these parameters will lead to aperiodic disturbance in the control system.Then the periodic current harmonic disturbance will be caused by the dead-time effect and the current sampling error caused by the hall effect sensor.And the external disturbance is mainly the load disturbance,load mutation is also a common problem in servo system,which will greatly affect the control accuracy of the control system.For the high-precision PMSLM control system,these disturbances will cause the PMSLM to produce a lot of harmonics,affect the thrust output,which will lead to the decline of motor positioning accuracy,poor product cutting surface and other consequences.In order to achieve stable thrust and high positioning accuracy,the active disturbance rejection vector resonant control strategy is proposed in this paper.The research contents are as follows:At first,the mathematical model of PMSLM is derived in the synchronous rotating coordinate system.The reason is that PMSLM AC motor is a complex nonlinear multi-variable system,so,it is not easy to control it directly.In order to control linear motor more simply and efficiently,the idea of coordinate transformation is adopted in this article,based on the PMSLM mathematical model in dq coordinate system,the periodic and non-periodic disturbances which cause current harmonic in velocity loop and current loop are analyzed,the disturbance caused by the inverter and the disturbance caused by the current sampling error are modeled and deduced.Secondly,the paper aims at the current harmonics caused by various disturbances in the control system,an active disturbance rejection vector resonance controller is designed.First of all,aiming at the periodic harmonic disturbance in the control system,an improved vector resonance controller is designed,which enlarge the bandwidth and reduces the phase delay compared with the ideal resonance controller.Then,in order to improve the robustness of the vector resonant,an improved ADRC is designed and linearized on the basis of the traditional nonlinear ADRC.As you can see from the simulation,the active disturbance rejection and resonance controller can suppress the current harmonics caused by the internal disturbance.Then,in order to suppress the external load disturbance to the control system,further enhance the disturbance suppression effect of the controller,on the basis of ADRC,an Internal Model Disturbance Observer(IMDO)and a Load Disturbance Observer(LDO)are adopted respectively to observe the disturbances,and the observed values are used as current feedforward compensation,to achieve the effect of load disturbance suppression,so as to improve the thrust quality of motor.Finally,a PMSLM experimental platform composed of AD5435 simulation system,driver board and host computer is built,and a series of contrast experiments of external load disturbance and thrust fluctuation is carried.According to the results of the experiment,the proposed active disturbance rejection vector resonant control method can suppress the periodic and non-periodic disturbances in the control system,reduce the current harmonics,improve the speed stability and reduce the thrust fluctuation.