Study Of Pneumatic Position Control System Based On Proportional Valve Of Direction Type

Since pneumatic system has the advantages of low cost, simple construction,reliable in work, no air pollution, it has been widely used in the fields of factoryautomation and robot driving system. However, the inherent characteristics of thepneumatic system, such as the condensability of the air, nonlinear of valve, frictioncharacteristic of pneumatic cylinder and easily influenced by environment factors,greatly increased the control difficulty in a degree, and hard to satisfy the orientationrequest in industry.Based on the characteristics of pneumatic position system with proportional valveand single piston, a high precision control of the system is achieved by researching andsimulation analysis of the control strategy.First, a nonlinear mathematic model is built, the characteristic is researched, andthe affect of system parameters to the characteristic is discussed. The Step PID controland Self-adaptive Fuzzy-PID control are put forward. The input signal is approached tothe expect position length by length through Step PID control which can stable theobject and adapt to the request of high precision orientation control. By fuzzyreasoning, the PID parameters can be adjust on line, and its value is changed dynamicso as to keep the optimal state at every moment in order to obtain the approvingcontrol effect.Second, the simulation interface is designed by using the MATLAB/SIMULINKtool. The characteristic in time and frequency domains of the system is analyzed indetail. The simulation is done to the step PID control and self-adaptive Fuzzy-PIDcontrol method. The results show that: compared to the traditional PID control method,Step PID control can improve the respond characteristic and orientation precisionclearly. The simulation result of orientation precision is under 0.1 mm. The overshootis 0.07 percent by Self-adaptive Fuzzy-PID control, and steady error is 0.07 mm. Thiscontrol method is combined with excellences of agility and strong adaptability ofFuzzy control and high precision of PID control, and has strong robustness.Last, a dynamic simulation is done. The results validate the correctness ofmodeling and the control methods.