Neural Network Based Active Disturbance Rejection Control of a Novel Electrohydraulic Servo System for Simultaneously Balancing and Positioning by Isoactuation Configuration

Qiang Gao,Runmin Hou,Chao Wang,Zhan Sun,Yuanlong Hou,Kang Li

doi:10.1155/2016/4921095

Qiang Gao, Runmin Hou + Show 4 more

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https://doi.org/10.1155/2016/4921095

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Abstract

To satisfy the lightweight requirements of large pipe weapons, a novel electrohydraulic servo (EHS) system where the hydraulic cylinder possesses three cavities is developed and investigated in the present study. In the EHS system, the balancing cavity of the EHS is especially designed for active compensation for the unbalancing force of the system, whereas the two driving cavities are employed for positioning and disturbance rejection of the large pipe. Aiming at simultaneously balancing and positioning of the EHS system, a novel neural network based active disturbance rejection control (NNADRC) strategy is developed. In the NNADRC, the radial basis function (RBF) neural network is employed for online updating of parameters of the extended state observer (ESO). Thereby, the nonlinear behavior and external disturbance of the system can be accurately estimated and compensated in real time. The efficiency and superiority of the system are critically investigated by conducting numerical simulations, showing that much higher steady accuracy as well as system robustness is achieved when comparing with conventional ADRC control system. It indicates that the NNADRC is a very promising technique for achieving fast, stable, smooth, and accurate control of the novel EHS system.

Highlights

Large pipe weapons, arms of heavy machineries, industrial robotics, and space-borne manipulators possess a sort of long and heavy linkages which have high ratio of length to diameter and time-varying unbalancing torque induced by the misalignment between its gravity center and the corresponding trunnion
In the electrohydraulic servo (EHS) system, the balancing cavity of the EHS is especially designed for active compensation for the unbalancing force of the system, whereas the driving cavity is employed for real-time positioning and disturbance rejection of the large pipe
Parameters for the tracking differentiator (TD) were h = 0.01 and r = 0.12, and those for the nonlinear state error feedback (NLSEF) are set as β1 = 0.95, β2 = 10.6, β3 = 17.3, c0 = 0.25, b4 = 2.5, b5 = 2.0, b6 = 1.5, and γ0 = 0.01

Summary

Introduction

Arms of heavy machineries, industrial robotics, and space-borne manipulators possess a sort of long and heavy linkages which have high ratio of length to diameter and time-varying unbalancing torque induced by the misalignment between its gravity center and the corresponding trunnion. The unbalancing torque serving as a sort of strong disturbance highly deteriorates control performances of the system [1, 2]. There are two kinds of system balancing strategies, namely, the external force based system balancing and the internal driving based system balancing. The external methods mainly depended on adopting proper balance weights or adopting balance machinery, and the static unbalancing components can be well compensated. The unbalancing part including partial static and dynamic unbalancing components was treated as external disturbance and further compensated during active control of the system. Regarding the large diameter of the pipe, the unbalancing components were heavy, highly challenging the control system for positioning [3, 4]. The currently adopted method based on direct driving was essentially a feedforward inverse compensation strategy, and it cannot achieve real-time balancing.

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