Research On Driving System Control Strategy Of A Permanent Magnet Linear Synchronous Motor

The research theme of this dissertation is focused on control scheme of Permanent Magnet Linear Synchronous Motors (PMLSM). In order to satisfy the requirement of servo system with high performance, it is necessary to design the controller of self-adaptability and higher anti-disturbance with fast speed response and robust stabilization. Based on the research of the PMLSM mathematic model and control theories, a PMLSM feed system is established. The dynamics, optimization and control strategy as well as some key technologies of the PMLSM feed system are studied by combining theoretical analysis with computer simulations.The content of this research falls into the following:In chapter 1, the background and significance of the research are stated. The development trend and the current research situations of the PMLSM servo system are introduced in detail. And the main content of this dissertation is proposed.In chapter 2, the relative basic knowledge is introduced briefly, and based on analyzing the space vector transfer laws of the PMLSM, the mathematics model of PMLSM is built. Then the d-q synchronous coordination and the thrust equation of the PMLSM are deduced. At last, the control method, block diagram and principle of the PMLSM rotors flux linkage orientation are obtained.In chapter 3, based on the basic analysis on PMLSM DTC principle, the detail function and realization of the sub-modules of PMLSM DTC are discussed. A set of PMLSM control strategies are presented, which are realized by selecting the proper voaltage vector according to the thrust error and the simulation platform are presented. The simulation result proves that this set of strategies is effective in theory compared with the classic method. These new methods not only give fast response, but also improve distinctively the steady states of the pulsation of the flux linkage and the thrust. In chapter 4, although the direct thrust control method has simple structure and is easy to be realized, higher parameter precision is required for it. In order to overcome the blight caused by parameter variation and outside disturbance in the PMLSM control system, the variable structure sliding mode control method is used. The method gives fast response and is robust and simple, so a high performance servo system can be obtained with DTC and VSSMC combined.In chapter 5, because of the nonlinear elements existing in the PMLSM feed system,a global-stable back-stepping nonlinear controller is designed step by step according to the inner relationship between the motion equation and its parameters. Then a Lyapunov function is found to check the stability of the designed nonlinear controller, and the analyzing result demonstrates that the nonlinear controller is asymptotic stable. Simulations demonstrate that the performances of the nonlinear controller are much superior to those of the PI velocity controller that has been widely used in motion control.In chapter 6, the study contents and conclusions of the dissertation are summarized, and the further research works are forecasted.The novelties of this paper are as followings:First, the direct thrust control method is introduced to the PMLSM drive successfully. Based on thrust error or fuzzy set of thrust error, the proper voltage vector is selected according to the requirement of thrust, so the pulsation of the thrust is reduced and dynamics and stability performance are improved.Second, the DTC is combined with varivable structure sliding mode control method which is of fast response, good robstness and simple structure. High performance AC servo system—based on adaptive variable structure siding mode control DTC for PMLSM (ASMC-DTC) is effective to overcome the disturbance of the parameters variation.Finally, because of the nonlinear characteristics, machine parameters are not fixed in the operation. Back-stepping method is introduced, which is a kind of anti-disturbance adaptive controller.