Research On Active Disturbance Rejection Control Of A High-pressure Electro-Pneumatic Position Servo System

In this paper,the research on active disturbance rejection control of high-pressure electro-pneumatic position servo system is carried out.In response to the characteristics and needs of the driven high-power high-pressure gas flow valve with high working pressure,high output power,fast response and high precision of the spool,a high-pressure electro-pneumatic position servo system that uses a high-pressure electric-pneumatic servo valve as a control element and a double-acting cylinder as an actuator was developed.However,high-pressure air has the characteristics of strong compressibility and expansion,and low viscosity.The high pressure of the gas leads to the increase of gas flow force of the servo valve and the increase of the load of high-pressure electro-pneumatic position servo system.The accuracy of the control becomes worse,and even the servo system is prone to oscillation,which makes it difficult to control the high-response electro-pneumatic position servo system with high response and precision.Therefore,to obtain better dynamic and static performance and anti-interference ability,this paper has carried out research on active disturbance rejection control of high-pressure electro-pneumatic position servo system based on the compensation control of the gas flow force of the high-pressure electro-pneumatic servo valve.The main research contents are as follows:1)The principle design and prototype development of the high-pressure electro-pneumatic position servo system.The working principle of the high-pressure electro-pneumatic position servo system were proposed,and mathematical model was built.The influence of different parameters on the performance of a high-pressure electro-pneumatic position servo system was analyzed through numerical calculation,and some key parameters were determined.The system’s structural design and prototype development were completed,and all indicators met the requirements.2)Aiming at the problem that the position of the spool of the high-pressure electro-pneumatic servo valve is seriously affected by gas flow force,the study of active disturbance rejection control was carried out.A linear active disturbance rejection control(ADRC)was designed based on the mathematical model of the servo valve,and the observation capability of the linear extended state observer(LESO)under different observer bandwidths was analyzed in the frequency domain.The closed-loop transfer function of the high-pressure electro-pneumatic servo valve under the control of PID,ADRC,and model-based ADRC with model information was solved and it was proved in the time domain and frequency domain that model-based ADRC has the best anti-disturbance ability.The variation range of the system parameters under the stable conditions of the closed-loop system with model-based ADRC was presented.The non-dominated sorting genetic algorithm with elite strategy(NSGA-Ⅱ)was used to adjust the parameters of model-based ADRC.Finally,simulation and experiment proved that the spool displacement under model-based ADRC has stronger robustness and better anti-disturbance ability.3)The control performance of the high-pressure electro-pneumatic position servo system was studied.The open-loop transfer function model of the high-pressure electro-pneumatic position servo system after linear simplification was analyzed,and a control strategy that uses a combination of nonlinear ADRC and linear ADRC to control the first and second stages of a two-stage position control system was proposed,and a third-order nonlinear ADRC controller was designed.The simulation results showed that two-level ADRC has better dynamic and static performance than two-level PID,and has a smaller position offset and shorter recovery time under different disturbances,indicating that two-level ADRC greatly improves the control performance and anti-disturbance ability of the high-pressure electro-pneumatic position servo system.