Output feedback motion control of pneumatic servo systems with desired compensation approach

Abstract

In this study, an output feedback control strategy for the pneumatic asymmetric cylinder is established by integrating a robust controller with the proposed desired compensation adaptive law and extended sliding mode observer (ESMO). Specifically, in order to attenuate the parametric uncertainties, a desired compensation indirect-type estimation method, based on physical model and desired system states, is designed to achieve estimates of model parameters, and the parameter estimation error can be regarded as part of the lumped uncertainties. Since only displacement signal is available, both the unmeasured system states and lumped uncertainties are estimated by the proposed ESMO, and the global stability is guaranteed by the presented robust control law. As a result, structured (i.e., parametric uncertainties) and unstructured (i.e., lumped uncertainties such as unmodeled dynamics, external disturbance and parameter estimation error) uncertainties can be handled and compensated, respectively, in one controller. The comparative experimental results indicate that the prescribed tracking trajectory can be achieved by the proposed controller in the presence of time-varying uncertainties.

A new compressible flow model for pneumatic directional control valves

“…The model of Bobrow and McDonell 26 has been further modified to include all these effects. The new flow model is proposed as in equation (7) where the equation of the new flow function is presented in equation ( 8) as…”

“…In these systems, the control of pressure, position, or velocity parameters is usually performed by controlling the mass flow of the air via a control valve. [6][7][8][9] Thus, the system of interest must be known to some extent, especially for the model-based control strategies, wherein the correct implementation of system model is crucial to meet the desired control performance. It is to be noted that the nonlinear relationship between the mass flow rate of air and the pressure dynamics makes the modeling issue a tedious task.…”