Modeling and experiment of pneumatic position system with spring-and-diaphragm actuator

Abstract

In this paper a nonlinear and continuous model of Pulse Width Modulation (PWM)-based pneumatic position system with diaphragm-and-spring actuator is presented via theoretical analysis; against experimental data, the unknown parameters are identified by Particle Swarm Optimization (PSO). Using open-loop tests, the experimental data are obtained by controlling the on/off valves with three different duty ratios: 50, 80, and 100% over a period of 100 ms. The analytical-experimental comparisons show the validity of the model. The modeling is useful for intelligent valve positioner algorithm design, control valve optimization design and actuators fault diagnosis.

Dynamics of Single-Action Pneumatic Actuators

“…Moreover, such effects occur for different types and executions of single-action actuators. It should be mentioned that the asymmetry of the dynamics is a factor to consider when developing a control system [9][10][11][12] or auto-tuner intended for positioners of the final electro-pneumatic control elements [13,14]. A systematic explanation of a phenomenon of asymmetry in the dynamics together with energy transformation issues is given based on the phenomenological (Sect.…”

“…Typically, a set of simplifications and assumptions are adopted to develop a useful model. This is also the case in the present study because the aim is to describe the observed dynamic behavior of the single-action actuator, rather than the sophisticated physics behind it, as described in [9,15,16].…”

“…Below, we attempt to explain this phenomenon. Clearly, a chamber discharge follows a general equation (9). However, in this case, the air mass flow is proportional to the air density under pressure P 1 instead of P 2 , as during charging process.…”