Finite‐Time Disturbance Observer‐Based Nonlinear Robust Adaptive Control of Hydraulic Manipulator With Parameter Identification

ABSTRACT Hydraulic manipulators exhibit strong coupling, pronounced nonlinearities, and significant modeling uncertainties, which hinder high‐precision motion control. This paper proposes a finite‐time disturbance observer–based nonlinear robust adaptive control (RAC‐FTDO) framework enhanced by a physically consistent dynamic parameter identification scheme. The entire system dynamics, including the hydraulic dynamics, is first derived. A weighted least squares approach is employed to obtain inertial and friction parameters under physical constraints, enabling reliable feedforward compensation. Building on back‐stepping principles, an adaptive controller systematically integrates an FTDO and a nonlinear robust strategy, enabling rapid and accurate estimation and compensation of both parametric uncertainties and unmodeled disturbances, while suppressing residual estimation errors and avoiding high‐gain feedback. Through Lyapunov stability analysis, the proposed controller achieves improved transient behavior and asymptotic tracking performance. The proposed approach can be extended to multi‐degree‐of‐freedom serial systems and has been experimentally validated on a hydraulic manipulator against several benchmark controllers, demonstrating its effectiveness.