Design And Implementation Of Control Strategy In BiPAP Ventilator

BiPAP ventilator is a device that assists human breathing and has good therapeutic effect on sleep apnea syndrome and chronic obstructive pulmonary disease.This thesis studied the control strategy of the BiPAP ventilator according to the functional requirements of the BiPAP ventilator in the home use scenario,and completed the relevant software design and testing,which was of great significance to break the monopoly of similar foreign products and enhance the competitiveness of domestic products.This thesis completed the design of the BiPAP ventilator control strategy,including the design of the pressure control algorithm and the design of the key detection algorithm,based on the ventilator hardware platform in the laboratory,with the goal of achieving accurate pressure control and comfortable and accurate human-machine synchronization.After completing the software design,the core functions of the BiPAP ventilator,such as respiratory synchronization and pressure switching function,respiratory event detection and ventilation adjustment function,and respiratory parameter calculation function,were realized.First,by reading relevant literature and researching similar products,we understood the treatment principle and ventilation mode of the BiPAP ventilator,and clarified the performance indicators and functional requirements of the ventilator according to relevant standards,and started research on pressure control and detection technologies that are relatively backward in domestic products.According to the characteristics of the BiPAP working mode of the ventilator,this thesis innovatively proposed a fuzzy-PID dual-mode control algorithm based on the switching of the breathing state in order to improve the user's comfort.Through the analysis of the hardware structure of the ventilator and the reading of related literature,it was found that the controlled system is difficult to establish an accurate mathematical model,and its characteristics are related to the user's breathing state.In order to solve the contradiction between the stability and the adjustment speed of the PID control algorithm when the pressure is switched in the BiPAP mode,this thesis designed a dual-mode controller that uses the fuzzy control algorithm in the pressure rise phase and the PID control algorithm in the pressure steady phase,which meets requirements of rapidity and accuracy,and the speed of pressure change can also be adjusted to meet the requirements of comfort.The fuzzy-PID controller was designed by MATLAB,and the approximate model of the system was used for simulation,which shows the effectiveness of the controller.In this thesis,the key detection algorithm of the BiPAP ventilator was studied.According to the change law of the airway flow when the patient breathes,the breath triggering algorithm,breathing event detection algorithm and ventilation adjustment algorithm were designed.In view of the shortcomings of the traditional flow threshold triggering algorithm that is easily affected by air leakage,this paper proposed a triggering algorithm based on flow rate and flow rate of change,which can resist leakage interference.For breathing events,this thesis proposed an apnea detection algorithm based on flow value fluctuations and a low-ventilation detection algorithm based on tidal volume.In addition,this thesis designed two methods of ventilation adjustment in different ventilation modes.Based on the designed algorithm and the ?C/OS-II operation system,this thesis completed the design of multi-task software including the data processing task,pressure control task,respiratory state switching task,and respiratory event detection and processing task.The finite state machine for breathing state was designed to realize the detection and switching of breathing state,the detection of breathing parameters and the detection and processing of breathing events,and achieved a good man-machine synchronization effect.Finally,this thesis tested the pressure control effect of the ventilator,the detection function of respiratory events and the accuracy of respiratory parameters.The test results showed that the pressure control effect of the ventilator had reached the expected level,and it could accurately detect apnea and hypopnea events.The calculation error of its breathing parameters was small,which met the requirements of relevant standards and achieves the expected design goals.