Design Of Ventilator Circuit And Air Structure And Research Of Fan Control Scheme

If pilots suffer from Obstructive Sleep Apnea Syndrome(OSAS),their ability of aircraft operation will be weakened,thus leading to a threat to aviation safety.The ventilator is the key against the OSAS,which can effectively perform the monitoring,prevention and treatment tasks.At present,the research of ventilator in China,especially high-end intelligent ventilator,is still in its infancy.In order to build a smart plantform for advanced ventilators,a control circuit and air structure is put forward and a position sensorless fan control program is realized based on ventilator R&D project.Firstly,by considering the functional requirement and breaking down the system into function modules,a control circuit,which based on STM32F405,is designed with highlight of the safety,EMC,heat dissipation,testability and cost factors.Secondly,an overall air structure,which consists of parameter measurement section,medical bellows and mask,is proposed.For parameter measurement,a special flow measurement method is exploited,which makes good use of throttling device to transform the pressure difference into flow rather than directly uses an integrated flow sensor.The rationality of the method is verified by finite element numerical simulation and the conversion formulas between differential pressure and flow is calibrated through experiments.Thirdly,a specific fan is selected,as well as a control scheme(field oriented control based on Luenberger observor)is adopted as the fan drive strategy for the ventilator application environment.Besides,the PID prior parameters are obtained through simulation.Fourthly,the fan control program is realized,especially,an open-loop start method is used to perform self-starting of the motor without a position sensor,which overcomes the unreliable low-speed performance of the Luenberger observer.Above all,the experiment result shows that the ventilator control circuit has a good electrical connectivity and reasonable power supply design.Besides,the peripherals are driven successfully and circuit board can run stably for a long time.The results of flow measurements in throttle device meet the expected requirements.The fan control performance is good enough to meet the control requirement during the ventilator treatment process,not only in pressure regulation dynamic response but also in stable pressure fluctuations.