Active disturbance rejection adaptive control of multi‐degrees of freedom hydraulic manipulators
Xin Sun, Jianyong Yao, Wenxiang Deng
Abstract
Summary This article investigates the precise motion control of multi‐degrees of freedom (DoF) hydraulic manipulators, and proposes an active disturbance rejection adaptive control (ADRAC) architecture based on full state feedback with consideration of both unmatched and matched uncertainties, that is, parametric uncertainties and uncertain nonlinearities. The new control strategy integrates adaptive control with extended state observer (ESO) via the backstepping method. Parametric uncertainties are handled by the synthesized adaptive law, and ESO is designed to estimate the remaining uncertainties before being compensated in a feedforward way. In particular, the unmatched and matched uncertainties can be observed in real‐time by constructing an ESO for each channel of the hydraulic manipulator system. The burden on ESO should be greatly reduced since parameter adaptation offsets most parametric uncertainties. Accordingly, high‐gain feedback is avoided in the resulting controller, and improved servo performance can thus be expected. In theory, the suggested ADRAC controller can attain asymptotic tracking performance under the influence of not only parametric uncertainties derived from various hydraulic parameters but also invariant disturbances. Furthermore, when uncertain nonlinearities become time‐variant, prescribed transient tracking performance and final tracking accuracy can also be ensured. Comparative simulations concerning both matched and unmatched uncertainties are obtained to illustrate the high tracking performance nature of the developed control algorithm.