| The traditional gantry motion platform with rotating motor and rolling lead screw can not meet the needs of high-precision automatic machining for its low transmission accuracy and stability,while the gantry motion platform driven by permanent magnet linear synchronous motor(PMLSM)has the advantages of having simple mechanical structure,strong environmental adaptability,and superior motion characteristics at high speed,which is more and more favored in industrial automation industry.However,due to the special structural characteristics of the gantry platform,two parallel axis motors couple together mechanically,and PMLSM itself is easily affected by uncertain factors such as external load disturbance and thrust fluctuation,which greatly restrict high efficiency and high precision of the moving platform.Therefore,it is necessary to design a high reliability and high precision control algorithm to break the development bottleneck of linear motor gantry platform.The research object of this thesis is a high precision gantry motion platform composed of three groups of PMLSM,which has two parallel y-axis with two similar PMLSMs and one linear drive guide rail with an identical PMLSM.The movers of the two Y-axis motors are connected with a cross beam,and the cross beam carries the X-axis PMLSM on it.However,The first issue to be solved is the insufficient accuracy of single-axis motor position tracking,and secondly,excessive synchronous position error of the Y-axis motor,which is caused by inconsistent load disturbances on both sides of the Y-axis when the platform is running to different positions.Therefore,contents of this thesis are as follows.1.Inland and overseas development trend and research status of high-precision gantry motion platform is investigated.The characteristics of platform driving methods and type of disturbance influence are explored,and control methods for the gantry platform are summarized.Combined with the control principle of PMLSM,the kinetics analysis of the gantry motion platform is carried out in this thesis.And the corresponding simplification is performed to reduce the complexity of problem solving.And a platform mathematical model is built on the Matlab / Simulink software platform,to verify the feasibility of the mode by simulation.2.Combined with the principle of backstepping control,the terminal sliding mode control algorithm is used to enhance the single Y-axis position controller of the gantry platform,to improve the position tracking accuracy,speed up the system response rate,improve the chattering problem due to discrete switch control,as well as design an appropriate adaptive rate to suppress the impact of external disturbances on the system.Simulation is carried out on the MATLAB platform to observe the change of the motor position tracking curve when disturbance added suddenly,so as to show the effectiveness of the method to improve the anti-interference ability of the system.3.To improve precision of the dual-axis synchronous control of the gantry platform,a synchronous sliding mode control method,combined with fuzzy control,is proposed based on adaptive fuzzy sliding mode control.The sliding mode surface and its rate of change are used as inputs for fuzzy control,And the gain parameters of switching control and fuzzy control are adaptively estimated,respectively.Simulation is carried out on the MATLAB platform.By comparing the experimental results of the new method with the ordinary sliding mode synchronization control algorithm,it is confirmed that above method can effectively improve the synchronization position accuracy and reduce system vibration and noise. |
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