Evaluation of Flow Control Using PID versus Fuzzy Logic in an Electropneumatic Circuit for Pulmonary Ventilation Applications

High-tech commercial mechanical ventilators are designed to provide a constant and accurate flow, thus ensuring the precision of ventilatory treatment. Therefore, this research aims to evaluate the flow control in a prototype electro-pneumatic unit for mechanical ventilator applications using a PID versus a Fuzzy Logic method. Specifically, the intention is to determine if there is evidence of superior performance of fuzzy logic control over PID in this application. For this reason, the methodology is based on measurement and numerical analysis. The design of this research is quasi-experimental and conducted in a laboratory. Thus, samples of the data of the variables were taken at convenience under a pre-established scheme and conditions. In terms of the type of study, it is considered quantitative, experimental, and applied. The main results show that according, the Bland-Altman analysis both controllers meet the accuracy limits of commercial equipment. However, the fuzzy logic controller presented better standard deviation and difference limits, demonstrating greater reliability in the accuracy of results. Additionally, the PID control demonstrated quicker response times with a shorter settling time (between 0.32 and 0.43 seconds) than in the fuzzy logic control (between 0.43 and 0.77 seconds); moreover, the fuzzy control presents an improvement in the volume of 900 mL, highlighting the efficiency of this controller in conditions of higher demand. The results show that both the PID and Fuzzy Logic controllers meet the stability conditions of the Jury Test. The systems poles are within the unit circle of the Z plane, confirming the controllers stability. Also, the curve of the fuzzy control in the Nyquist analysis is farther away from the origin and from the point (-1, 0j) than the curve of the PID control, indicating better stability and a more robust system against variations or disturbances.