Research On Pneumatic Pressure Control System Based On Active Disturbance Rejection Double Closed Loop Control

Pneumatic systems have the advantages of energy saving,pollution free,low cost,safety,reliability and simple structure due to using air as the transmission medium.At present,they are widely used in robots,automobile brake devices,workpiece clamping and transportation on industrial production lines.With the development of ultra-precision processing technology,airfloating probes,air-floating guides,air-floating turntables and other equipment which can achieve low-vibration and almost frictionless relative motion,can satisfy the needs of ultraprecision measurement and high-precision positioning.These equipment put forward higher requirements on the performance of the pneumatic pressure control system.The traditional pressure control system has low accuracy and poor anti-disturbance performance.In the flow feedback control process,the unsteady flow measurement equipment is expensive and easily causes pressure loss.Therefore,traditional pressure control system is difficult to achieve a desired effect.This study proposes a double closed loop control method based on active disturbance rejection controller to optimize the dynamic characteristics and disturbance rejection performance of the pneumatic pressure control system.The flow measurement method based on the adaptive tracking differentiator is used to obtain a flow feedback signal with lowcost and no pressure loss.The main content is included as follows:(1)The overall scheme of the pneumatic pressure control system is designed.The selection and production are carried out according to different pneumatic components,the simulation experiment platform of this system is built,and the measurement and control program are written.(2)A double closed loop control method based on active disturbance rejection controller and integral controller(ADRC-I)is proposed.The physical model of pressure control system based on ADRC-I is established and simulated,and the mathematical model of proportional flow valve and isothermal pressure chamber are established.The results show that the antidisturbance performance of ADRC-I method is better than traditional PID method and PIDbased double closed loop control method(P-I).PID method has the problems of poor antidisturbance performance,contradiction between overshoot and anti-disturbance performance.P-I method has the problem of contradiction between overshoot and system bandwidth.However,ADRC-I method can achieve no overshoot,strong anti-disturbance,large bandwidth at the same time.(3)An unsteady flow measurement method based on adaptive tracking differentiator is proposed.An adaptive tracking differentiator based on pressure tracking error and differential size is designed to identify signal characteristics.The adaptive tracking differentiator is simulated using analog signals and actual signals,and a flow measurement verification experiment is carried out.The results show that the flow measurement method based on adaptive tracking differentiator can adaptively adjust the parameters of the differentiator according to the characteristics of the flow signal,and effectively measure the unsteady flow rate in a wide dynamic frequency range.Compared with the measurement method based on traditional differentiator,the adaptability of the measurement method based on adaptive tracking differentiator has been significantly improved.Compared with the measurement method using a laminar flow meter,it is no pressure loss and low-cost.(4)The performance evaluation experiment of the pressure control system based on ADRC-I is carried out.The experimental results show that the proposed flow measurement method can be used in the double closed loop pressure control system.The experimental results is consistent with the model simulation.The ADRC-I method is compared with PID method and P-I method,it can simultaneously achieve the effects of no overshoot,strong antidisturbance performance,and large system bandwidth.Therefore,this method can improve the anti-disturbance performance and coordinate the contradictions between overshoot and quick response of pressure control system.