Research On Ultra-Precision Feed Technology Based On Aerostatic Guideways

Aerostatic stage plays an important role in the manufacturing industry.With the rapid development of ultra-precision manufacturing technology,the smaller characteristics are required in practical production.Therefore,new demands about aerostatic stage are put forward.The future trend of precision motion stages is long stroke,high precision and high response.Traditional aerostatic stage based on servo motor with ball screw is difficult to satisfy new demands.Therefore,an aerostatic stage based on aerostatic guideways and linear motor is designed and presented in this thesis and the motion control method of aerostatic stage is studied based on this object.First,the mathematical model of linear motor thrust fluctuation is built up.Internal magnetic field of linear motor is analyzed with FEM.The thrust fluctuation data of linear motor is obtained under different current and position conditions.The thrust fluctuation data is processed by the method of function fitting.Finally the factors which influence the magnitude of the thrust fluctuation are studied,such as the current and position.Simulation results show that the relationship between the magnitude of the current and the thrust fluctuation is a linear function,the relationship between position and thrust fluctuation is a periodic function.The basis for the subsequent online estimation and compensation of the thrust fluctuation are established.Secondly,in order to reduce the system tracking error of the aerostatic stage,an acceleration feedforward PID control algorithm based on disturbance observer is proposed.During the start-up and stopping phases of the aerostatic stage,following error and balance time are reduced by the acceleration feedforward controller.The thrust fluctuations are suppressed and the tracking error of the system is reduced by the disturbance observer.The simulation results show that the acceleration feedforward PID control algorithm based on the disturbance observer is more effective than the traditional acceleration feedforward PID control algorithm and the acceleration feedforward fuzzy PID control algorithm,which could obviously reduce the following error caused by the thrust fluctuation of the linear motor.Finally,motion control algorithms experiment are executed on the aerostatic stage.The correctness of the linear motor thrust fluctuation mathematical model and the effectiveness of the acceleration feedforward PID control algorithm based on the disturbance observer are verified by experimental results.By using the designed algorithm,the tracking error of the system is reduced.And the impact of thrust fluctuations on the control precision of aerostatic stage is reduced too.