Research On Negative Pressure Servo System Based On Independent Structure Of Charging And Discharging

The negative pressure servo system is the core of the high altitude aircraft pressure simulation equipment.Based on the analysis of characteristics of charging and discharging at lower pressure,the paper propose the independent structure of negative pressure servo system with double servo valves to decrease the asymmetry and nonlinearity of negative pressure servo system.Combined with fuzzy PID control strategy,the negative pressure servo system gets dynamical characteristics improved at low pressure.The main contents of this paper are as follows:Firstly,the influence of dynamic characteristics of the pipeline pressure on negative pressure servo system is analyzed.Through the simulation analysis and experimental study of the pipeline pressure dynamic characteristics,the relationships among pipeline pressure transmission,pipe diameter and pipe length is revealed,which is the foundation for further study on the dynamical characteristics of the negative pressure servo system.Secondly,the mathematical model of the independent structure with double servo valves is established and also the system simulation platform is set up in detail.The simulation results that the structure with single servo-valve combined with the common PID controller can't deal with the asymmetry and nonlinearity of the system at low pressure,and the system control performance deteriorates severely with the decrease of the tracking pressure point.The independent structure with double servo valves can decrease the asymmetry and nonlinearity of the system,but it requires further treat to meet requirements of the dynamical characteristics of the negative pressure servo system.Thirdly,the nonlinear characteristics of the negative pressure servo system are analyzed.The fuzzy PID control strategy is proposed based on the independent structure with double servo valves.The simulation of the system is established on Matlab/Simulink platform and the control effects of various structures and controllers are compared and analyzed in detial.Finally,the experiment platform of the structure with single servo-valve and the independent structure with double servo valves is built to verify the reliability of the independent structure for decreasing the asymmetry and nonlinearity of the system at lower pressure and the effectiveness of the fuzzy PID control strategy.Above all,this paper proposes the independent structure with double servo valves and a suitable control strategy to decrease the asymmetry and nonlinearity of negative pressure servo system,which is valuable in engineering application and academic research.