FEspirator - pandemic ventilator is a project of the Faculty of Electrical Engineering, University of Ljubljana. It is intended for use in an event of a sudden shortage of medical ventilators. This project was inspired by the outburst of COVID-19 pandemic and in spring 2020 in the extent of a few weeks a working medical ventilator was made the faculty members and associates, which ventilates the patient by compressing a bag valve mask. Made and tested were two prototypes, v1 and v2, which were successfully tested on patient simulator in simulation department of University medical centre Ljubljana. Because the epidemic already got better at the time and we got enough medical ventilators, we didn’t make the devices in higher numbers, but we promptly used all the experience in the development of a new version, named FEspirator V3.
My task was development of the electronics for FEspirator V3. We developed and made electronics for this version entirely on one printed circuit board (PCB) with STM32G4 family microcontroller, powering from network or battery supply, needed sensors for controlling the compression of bag valve mask and sound alarm system. For the compression of bag valve mask we used a motor for power steering in a car, which receives requests for torque from microcontroller via CAN bus. On the previous version they used a different microcontroller of the same family and a motor controlled via power bridge with PWM signal, so some adjustments of the program code and a CAN communication interface were required.
We installed the circuit into prototype of the ventilator and connected it to the pneumatic circuit. We adjusted sensors for position, pressure and flow and set border values of torque for motor. After initial problems on the circuit and in communication with motor, which we solved successfully, ventilator started working as expected. It turned out that torque of the chosen motor exceeds the torque needed for this device and CAN communication needs to be optimised do that we could get the desired response time under 10 ms.
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