Research On Robust Control For Ironless Linear Permanent Magnet Synchronous Motor

Taking the project supported by specialized research fund “Study on High Speed andHigh Precision Numerical Control Machine Linear Servo Motor Normal Force Fluctuationand Optimal Control Strategy” for the doctoral program of education as background, theresearch object of the thesis is the ironless linear permanent magnet synchronous motor(ILPMSM) control system. According to the characteristic of ironless linear permanentmagnet synchronous motor and the requirements of strong robustness and high precision,the robustness theory, delay compensate and hunting suppression are combined to researchthe d-q axis coupling problem and the problem of the system affected by uncertaintyincluding load disturbances and parameters variations. The main contents are as follows:A robust controller with a system delay compensation is designed for the ILPMSMsystem with unknown system parameters based on the nonlinear decoupling for theproblem the system affected by uncertainty due to the ILPMSM taking direct drive mode.The proposed control scheme is applied for ILPMSM system current and velocity controlto reduce disturbance due to the d-q axis coupling effect, modeling uncertainty, frictionand so on. One of the advantages of the proposed controller is relatively simple, and allowssystem steady-state output to be equal to input. The system delay compensation adopts aninverse system delay model to compensate the power devices transport delay effect. As aresult, the proposed controller does not need to be combined with other control algorithms.Another advantage of the proposed controller is that it does not need to known systemparameters precisely.The dynamic performance of an ILPMSM system with non-linear element, such asdead zone and saturation, is analyzed based on the linear system theory and describingfunction method. The limit value parameters of the PI controller are obtained. Thenon-linear element refers to the system generates limit cycle, resulting in a series ofsustained oscillations and turns instability. To eliminate the non-linear effect on the servosystem, the relationship between the velocity error and dead zone parameters is established and a dead zone model is proposed to modify the output of PI controller parameters. Theresult of simulation shows that the designed dynamic inverse model can totally compensatethe influence of the nonlinear system and the servo system can meet the requirement ofrobustness.