Research On Precise Pressure Regulation And Air Supply Technology For Aviation Oxygen Mask

High-altitude and high-speed flight is one of the technical characteristics of a new generation of fighter aircraft,which places higher requirements on the pilot’s oxygen supply system.In response to this problem,this article had carried out the following main research work.This article first summarized the research status of aviation oxygen supply system and pressure-regulated air supply technology at home and abroad from two aspects of structural design and control strategy research.Secondly it studied the physiological requirements of aviation oxygen system for the safety of flight crews.On this basis,the technical requirements of this subject were put forward,and the theory and test analysis were carried out for the key structure used for pressure regulation and gas supply.On the premise that its steady-state characteristics and dynamic response met the technical requirements,the overall design of the aviation oxygen mask pressure-regulating air supply system based on the proportional flow valve was proposed.Then,based on the overall scheme of the aviation oxygen mask pressure regulating air supply system,various subsystems such as proportional valves,simulated lungs,one-way breathing valves and connecting pipelines were theoretically analyzed and mathematical models were established.The key structural parameters were systematically identified in combination with test experiments.The above models were simulated on MATLAB/Simulink and AMESim software platforms,and three types of open-loop control system models for pressure-regulating air supply were completed.A constant signal was input to the system and the output control results of the three simulation models were compared,indicating that there was still a certain gap compared with the target pressure.The Simulink model would be selected for better control strategy research and simulation.Based on the test data of the physical model and the simulation results of the mathematical model,the control strategy of the aviation oxygen mask pressure-regulating air supply system was researched.Firstly,the traditional PID control method was applied to the controlled system.Besides,the simulation results of PID controller combining with the fuzzy control which could self-tuning parameters in real time were analyzed to find the deficiencies and optimize the structure size parameters as much as possible.Taking into account the nonlinearity and complexity of the controlled system,a sliding mode variable structure controller combined with a fuzzy system was designed.The simulation results showed that under this controller,the pressure fluctuation range in the oxygen mask was reduced by two-thirds,maintaining the pressure difference between the inside of the mask and the lungs of the human body within a safe range.At the same time,the introduction of the fuzzy system eliminated the chattering phenomenon caused by the sliding mode controller,which made the system fluctuate less when the target pressure changed and improved the comfort of the human body,which theoretically achieved the goal of precise pressure regulation and air supply and laid the foundation for subsequent experiments.Finally,a test plan for the pressure-regulated air supply system was proposed.The hardware equipment based on different subsystems was selected to build the test device.An active breathing simulator based on PLC control with continuously adjustable respiratory rate was designed.First,the performance of the entire test bench was tested by controlling the pressure of the fixed volume cavity,and then the aviation oxygen mask was tested by adjusting the pressure and supplying air with different control methods.When the air supply pressure was0.3MPa,and the 2k Pa pressure step signal was input for 2s,the Fuzzy sliding mode control had a better effect that the pressure fluctuation range in the mask was ±480Pa and the target steady-state value could be reached within 1s.And the test was basically consistent with the simulation pressure fluctuation trend and range,which kept the tracking error within ±210Pa.This method had better followability and faster response,and achieved the purpose of precise pressure regulation and air supply to a certain extent.