Pneumatic Stable Pressure Source With High Accuracy And Two Closed-loops Series For Instruments

With the increase of application of high precision pneumatic insruments, itputs forward higher requirements for stability of gas pressure. In accordance with thelack of pneumatic stable pressure source on the market at present, this thesis presentsa method with two closed-loops series together taking into account that some gascomponents and instruments require higher accuracy and stability of pressure control.The work comprises a series of tasks and they are as follows.Firstly, two closed-loops series feedback control method was introduced intopneumatic stable pressure sources system, and its structure was designed. Themathematical model of inflation and deflation with single sealed gas chamber of thesystem was established, then time changes of the inflation and deflation underdifferent gas source pressure, gas source temperature and chamber volume simulated.Correctness of the simulations was verified by experiments.Secondly, proper components were chosen and hardware experiment platform ofstable pressure source built. Special control software was programmed based onLabView platform which comprised four sub-function modules of data acquisition,PID control, parameter settings and manually control. The software also has functionsof storing experimental data and visualizing wave and tendency in real time.Thirdly, a series of experiments were carried out under different gas chamberpressure, PID target pressure value and difference between target and initial pressureto explore the response characteristics of the system. Then measurement wasconducted to estimate the ability to stabilize of the system when there existed flow atthe end of equipment. The results illustrate that when the difference between pressuretargets of two chambers is maintained at more than0.2MPa, the system has a goodability to regulate. Different gas chamber pressure, PID target pressure value anddifference between target and initial pressure have different impacts on systemcharacteristics. When flow rate is15L/min, the stabilization errors are always maintained within2%which indicates that this pneumatic stable pressure source withtwo closed-loops series has a good stabilizing effect.Research of this thesis provides a basis for high accuracy pressure servo controltechnology and a beneficial exploration for reducing pressure fluctuations with gasflow.