Research On Pneumatic Pressure Source With High Precision

Nowadays pneumatics is more and more used in various industrial and civil fields. Recently people make a lot of researches on pneumatic servocontrol system of position or velocity. But research on pneumatic pressure servocontrol system is rare. A pressure signal with high precision and response is required to generate in some simulation of practicality. In this dissertation in light of characteristics of pneumatic pressure servocontrol system performances of the system and different control methods are theoretically researched on. At last a pneumatic pressure source with high precision and response is achieved through experiments.Firstly, working principle of pneumatic pressure source is expatiated and a nonlinear mathematical model of the system is founded. By means of simulation effects on system characteristics of system parameters such as pressure of air supply, temperature of air supply and volume of closed chamber are discussed.Secondly, three control algorithms applied to the system are studied. Though a classic control algorithms (e.g. PID control) can attain good control effect under some circumstance it has drawbacks that it is difficult to adapt to change of system parameters and to tune control parameters. It is because of the serious nonlinearity of pneumatic system. A hybrid of Fuzzy and PID has advantages of not knowing accurate model of system and good adaptive ability to the change of system parameters, which is suitable for the pressure servocontrol system. A Fuzzy-PID controller is successfully designed in the dissertation and simulation results suggest that the system with the Fuzzy-PID controller can obtain good static and dynamic behavior.Finally, the pressure servocontrol system is set up. In experiments a flow servovalve as electric-pneumatic transducer is adopted to compose pressure control system with closed loop. At the same time software that not only implements the control algorithm but also provides an interface between the user and the system is programmed. The experimental results show the hybrid of Fuzzy and PID controller can attain high accurate and responsive control effects in pneumatic pressure servocontrol system. It is proved that the founded model can describe the system, characteristic analysis in theory is correct and the control strategy has feasibility and strong robustness. When adopted Fuzzy-PID control the overshoot of system response of step signal is no more than 2% and steady-state pressure error is no more than 1kPa.The researches of the dissertation lay down a good foundation for studying further pneumatic pressure source with high precision.