Modelling of a Positive End-Expiratory Pressure Valve with a Voice-coil Actuator

Abstract

The positive end-expiratory pressure (PEEP) valve is important in the regulation of the pressure at the patient airways in devices for mechanical ventilation. The goal of this work is to derive a model that sufficiently captures the dynamics of the PEEP valve to be used for model-based control design. This paper describes the development of a model for common PEEP valve designs, thus allowing an adoption for different devices. A simplified first principle model with one mechanical degree of freedom is derived, under the assumption that the valve’s membrane behaves similar to a massspring- damper system. Following a grey-box model approach, physical parameters were lumped together and experimentally determined or identified from acquired data. Therefore, a valve test bench was developed to record various series of measurements. It was possible to determine a suitable flow factor which describes the correlation between flow, valve opening and upstream pressure. Additionally, a damping coefficient was estimated, with which the model achieves a good fit to the measured data at low dynamics and flows.

Keywords

• positive end-expiratory pressure valve
• simplified dynamic model
• parameter estimation