Closed-loop Pneumatic Position Control Method

The pneumatic control systems play very important roles in the industrial automation systems owing to following advantages-simple in structure,low cost of the components,esay to keep clean to working environments,easy in power tranfer, high power-to-weight ratio,and so on.However pneumatic drives exhibit highly nonlinear characteristics due to the compressibility of air,the nonlinearity of valves etc.It is very diffcult to find an optimal controller to realize pneumatic system rapidly, accurately position servo control.Based on the characteristics of pneumatic position system with proportional valve and single piston,a high precision control of the system is achieved by researching and simulation analysis of the control strategy.First,a nonlinear mathematic model is built,the characteristic is researched,and the affect of system parameters to the characteristic is discussed.The Self-adaptive Fuzzy-PID control is put forward.By fuzzy reasoning,the PID parameters can adjust on line,and its value is changed dynamic so as to keep the optimal state at every moment in order to obtain the approving control effect.Second,the characteristic in time and frequency domains of the system is analyzed in detail by using the MATLAB tool.The simulation is done to self-adaptive Fuzzy-PID control method.The results show that:compared to the traditional PID control method this control method is combined with excellences of agility and strong adaptability of Fuzzy control and high precision of PID control,and has strong robustness.Last,a real time control is done by LabVIEW.The results validate the correctness of modeling and the control methods.