Research On Adaptive Cushion Of High-speed Cylinder Based On Pneumatic Servo Control

Pneumatic transmission systems are widely used in factory automation.Pneumatic cylinders are developed towards high speed,but it has been limited by cushion of piston in the end of stroke.Cushion can be built through cushion valve on the cover of cylinder.But once working condition changed,its proper cushion will be destroyed and resetting a proper cushion manually will take too much time.Pneumatic servo technology can be used to control the movement of cylinder to achieve cushion,and it can adapt to change of working condition by adaptive algorithm.So this paper focus on modeling and controller design of pneumatic servo system with purpose of achieving adaptive cushion of high-speed pneumatic cylinder.The movement of pneumatic servo system is researched,and the nonlinear model of servo system is obtained by equation of each part.In order to control the movement by linear theory,linear model of system is obtained by linearizing at operating point.The parameter of model is obtained by system identification.Through the model of pneumatic servo system,its performance is analyzed.It shows that pneumatic servo system has some characteristics such as low natural frequency,small damping ratio and bad dynamic performance.Considering the bad performance of pneumatic servo system,state feedback controller is chosen to control the pneumatic cushioning system.Speed and acceleration of piston are the state variable of the system and they can be obtained by sensors.The parameter of controller is calculated by pole assignment.The simulation and experiment model is constructed in Matlab/Simulink.The result of simulation and experiment shows that cushion is achieved by state feedback control,but when given signal or mass load is changed,the proper cushion will be destroyed.In order to adjust to working condition changes,a kind of model reference adaptive controller based on fuzzy logic is designed.The main controller is state feedback controller,and model reference adaptive component is designed by fuzzy logic to change the parameter of state feedback controller adapt to change of working condition.Fuzzy logic control is designed by fuzzy control toolbox of Matlab.The simulation and experiment model is constructed in Matlab/Simulink.The result of simulation and experiment shows that proper cushion of high-speed pneumatic cylinder is maintained when supply pressure,mass load or desired speed change.It can be said that adaptive cushion of high-speed pneumatic cylinder is achieved by the model reference adaptive controller.