Dynamical model averaging and PWM based control for pneumatic actuators

Abstract

Abstract-A pneumatic actuator with solenoid valves is a discontinuous-input system because each valve can be either in on or off state. For such an actuator, this paper proposes a sliding-mode control scheme based on an averaged continuousinput equivalent model for the open-loop system. The averaged model is obtained from the nonlinear dynamics of the open-loop discontinuous-input system undergoing pulse-width-modulation (PWM) at the input (i.e., valve open/close action). The PWM duty cycle will be regarded as a continuous input to the proposed averaged model, and thus generated by the proposed sliding-mode controller. By adjusting the PWM duty cycle, the controller switches between seven modes of operation of the open-loop system in order to select the ones with necessary and sufficient amounts of drive energy to achieve position tracking. We will show that this results in reduced position error and valve switching activity for the actuator. The proposed control scheme is experimentally used in the position control of a pneumatic actuator and the results are presented.

Average Modeling and Nonlinear Observer Design for Pneumatic Actuators With On/Off Solenoid Valves

“…The complete modeling can be divided into three parts: piston dynamics, air dynamics in each chamber and valves dynamics. Using Newton's second law and the first principle of thermodynamics, the piston dynamics and the air evolution inside each pneumatic chamber are given by [9,15,16,19]…”

“…In this section, we develop a position controller for our pneumatic actuator. The control strategy aims to make the piston position y tracks a desired sinusoidal trajectory y d with a sliding mode control strategy as in [19]. Let us define the position tracking error e p as e p = x 1a − y d To ensure that the control objective is respected and in order to consider neglected or non-modeled dynamics of the piston 2 , a dynamical uncertainty is introduced in the translation dynamic i.e.…”

“…Sliding mode control (see [10][11][12][13][14]) has also been considered as a promising control strategy for pneumatic systems due to its ability to account for the system nonlinearities as well as its dynamic uncertainties. The authors of [15][16][17][18][19] use averaging techniques to derive a nonlinear model which they use to design sliding-mode controllers to control the actuator position.…”

“…• In modeling and control design: the models of [9,[15][16][17][18][19] are output averaged models. In other words, they are partially averaged model as only the actuator position is averaged while the two pressures are still governed by switched dynamics.…”

Design and Implementation of a Pneumatic Servo System using Conventional Direction Control Valve

“…S. Hodgson et.al [3], investigated a sliding-mode control arrangement for the open-loop system depend equivalent model has an averaged continuous input, a PSS designed and implemented using a conventional directional control valve (CDCV).The model was developed the dynamics nonlinear of open-loop with discontinuous-input system undergoing PWM of the input (i.e., on/off action). The results showed reducing in error position and active switching valve for the actuator.…”