Title: Matrix sensitivity-based adaptive nonlinear iterative compensation controller for the force control system of hydraulic legged robots

Authors: Kaixian Ba; Jinbo She; Linyang Chen; Bao Xu; Yuan Wang; Xiaolong He; Xinrong Li; Ning Liu; Guoliang Ma; Bin Yu

Addresses: State Key Laboratory of Crane Technology, School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' State Key Laboratory of Crane Technology, School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China ' State Key Laboratory of Crane Technology, School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066000, China

Abstract: With the growing demand for tasks requiring effective force interaction between robots and their environments, the need for enhanced force control performance in hydraulic drive unit (HDU) has escalated. However, the inherent nonlinearities and coupling effects in HDU pose substantial challenges to achieving precise force control. This paper introduces a theory of matrix sensitivity control and proposes a matrix sensitivity-based adaptive nonlinear iterative compensation controller (MSANIC). Initially, the matrix sensitivity visually displays the implicit relationship between control input compensation quantities and predicted output state variations in nonlinear systems. Secondly, the real-time optimal model parameters of the feedforward compensation controller were determined, and adaptive control of the feedforward compensation controller was achieved. Finally, comparative experiments verified the superior performance of the proposed force control method, demonstrating its ability to significantly reduce error oscillations. This research provides a theoretical reference for the stable motion control of the legged robot.

Keywords: force control; hydraulic drive unit; HDU; hydraulic legged robot; matrix sensitivity; nonlinear iterative compensation.

DOI: 10.1504/IJHM.2026.155986

International Journal of Hydromechatronics, 2026 Vol.9 No.3, pp.383 - 404

Received: 27 Aug 2025
Accepted: 28 Sep 2025
Published online: 28 Aug 2026 *

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