Mechatronic Design and Active Disturbance Rejection Control of a Bag Valve-Based Mechanical Ventilator

This paper presents the mechatronic (mechanical and control system) design of a functional prototype of a portable mechanical ventilator to treat patients with a compromised respiratory function. The portable ventilator ensures adequate oxygenation and carbon dioxide clearance while avoiding ventilator-induced lung injury (VILI). Oxygen is delivered through the compression of a bag valve (Ambu bag) using a moving strap. Carbon dioxide is cleared through the control of a pinch valve actuated by a low-torque servomotor. The positive end-expiratory pressure (PEEP) is controlled by an adjustable mechanical valve of the system. An Arduino Mega microcontroller board is used in this prototype to control the respiratory variables. All mechanical components as well as sensors, actuators, and control hardware are of common use in robotics and are very inexpensive. The total cost of the prototype built in this work is about $425 U.S. dollars. The design is meant to be replicated and utilized in emergency conditions that involve an overwhelming number of cases, such as COVID-19 treatment, in places with no access to commercial mechanical ventilation (MV) technologies. In order to account for variations in the prototype as built, the software developed for this portable MV applies an active disturbance rejection control (ADRC) strategy. This control strategy is presented as a universal control structure for any mechanical ventilator able to supply air flow with controlled pressure and volume.