An Asymptotically Stable Pressure Observer Based on Load and Displacement Sensing for Pneumatic Actuators With Long Transmission Lines

Abstract

Pneumatic systems have regained popularity in robotics, with the new advances in the electronic valves that have enabled precise position control of pneumatic cylinders. Recently, the use of pneumatic systems has been extended to force and impedance control. Such new applications include tele-operated medical robotic systems with pneumatic transmission lines where more advanced system modeling and control is required. Pressures of a pneumatic actuator are commonly used to improve control performance. When direct pressure measurement is not available or not desirable for cost effective implementation, actuator pressures can be estimated by a model-based observer. This paper introduces a nonlinear pressure observer based on force and displacement sensing. The proposed algorithm allows to obtain asymptotic stability of pressure estimation error with an improved convergence. The presented method does not require a transmission line model and guarantees bounded stability in the presence of disturbance in force measurements, hence it is able to provide a robust pressure estimation. The effectiveness of the proposed observer is confirmed by performing force control experiments in a tele-operated pneumatic system. Index Terms-MRI-compatibility, pressure observer, teleoperated systems.

Observer based impedance control of a pneumatic system with long transmission lines

“…For this study, a critically damped impedance characteristic is selected as the reference. The efficacy of the presented observation scheme has been demonstrated by the authors, in an earlier study that involves a simple PI controller for force control [13]. As noted, the actuator pressures are generally used as states in the modelbased controller designs.…”

“…1. The proof of stability in the observer dynamics has been provided by the authors in an earlier study [13]. The observed pressure states are provided to a sliding-mode based non-linear controller.…”

“…In addition, the proposed observer guarantees a limited reduction in observation accuracy in the presence of measurement errors. The proof of the asymptotically stable pressure observation and the analysis of robustness has been provided by the authors in an earlier study [13].…”

Adaptive Backstepping Control of a Pneumatic System With Unknown Model Parameters and Control Direction

“…Pneumatic technology is widely used in various automation fields, due to its low-cost, cleanness, and high power-toweight ratio properties [1]. With the technology progress, the performance of pneumatic elements, e.g., the proportional valve, is increasing, while the prices of them are decreasing; at the same time, micro-controllers with high performance to price ratio are available for pneumatic servo systems control.…”

Pressure Observer Based Adaptive Dynamic Surface Control of Pneumatic Actuator with Long Transmission Lines

“…2019, 9, 3621 2 of 17 between the mass flows at the outlet and inlet of the line, as well as a formula for the pressure drop along the tube. Although this approach was later employed in many other studies (Jiang et al [14]; Richer et al [17]), it has been proven improper for long transmission lines (>2 m) [18]. Yang et al [8] adopted a first order transfer function with time delay to describe the 9-m transmission line dynamics.…”