Abstract

In existing methods, full-state feedback is required for the position tracking of single-rod Electro Hydrostatic Actuators (EHAs). Measuring a full state is not always possible because of cost and space limitations. Furthermore, measurement noise from pressure sensors may degrade the control performance. We propose an observer-based nonlinear position control with nonlinear coordinate transformation while only using position measurement to improve the position tracking of single-rod EHAs. The proposed method comprises a position controller and an observer. We propose a nonlinear coordinate transform for the controller design. The desired force is designed for the position tracking and boundedness of the internal state. The position controller is designed to track the desired state variables for the EHAs. Meanwhile, a nonlinear observer is proposed in order to estimate a full state using only the position measurement. The stability of the closed-loop system is investigated via an input-to-state stability property. The performance of the proposed method is validated via both simulations and experiments.

Highlights

  • Electro-Hydraulic Systems (EHSs) have been widely used in industrial systems because of their high power density, stiffness, and flexibility as compared with their electrical counterparts [1].valve-controlled hydraulic systems, where systems use a pressure-compensated or load-sensing pump to pressurize fluid for delivery to individual valve-controlled actuators, are widely used in industries because of their simplicity

  • We propose an observer based nonlinear position control while using nonlinear coordinate transformation to improve position tracking performance using only position measurement for single-rod electro-hydrostatic actuators (EHAs)

  • The position tracking performances in both the transient and steady-state responses were improved by the proposed method

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Summary

Introduction

Electro-Hydraulic Systems (EHSs) have been widely used in industrial systems because of their high power density, stiffness, and flexibility as compared with their electrical counterparts [1]. Valve-controlled hydraulic systems, where systems use a pressure-compensated or load-sensing pump to pressurize fluid for delivery to individual valve-controlled actuators, are widely used in industries because of their simplicity They pose several problems, such as environmental pollution that is caused by working fluid leakage, maintenance load, heavy weight, limited installation space, and low energetic efficiencies that are caused by throttling losses, even if their designs are simple [2]. Previous nonlinear control methods improved the position tracking of valve-controlled or pump-controlled EHSs, they require a full-state feedback. We propose an observer based nonlinear position control while using nonlinear coordinate transformation to improve position tracking performance using only position measurement for single-rod EHAs. The proposed method comprises a position controller and an observer. The performance of the proposed method was validated via both simulations and experiments

Mathematical Model of Electro-Hydrostatic Actuator
Nonlinear Coordinate Transformation h
Controller Design
Stability Analysis of Internal Dynamics
Nonlinear Observer Design
Stability Analysis of Closed-loop System h
Simulations
Experiments
Findings
Conclusions
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