Cable Estimation-Based Control for Wire-Borne Underactuated Brachiating Robots: A Combined Direct-Indirect Adaptive Robust Approach

TL;DR

This paper introduces an adaptive robust control framework for wire-borne brachiating robots, combining direct and indirect methods to handle unknown cable dynamics and disturbances, ensuring stable and reliable traversal.

Contribution

It proposes a novel combined direct-indirect adaptive control approach for underactuated brachiating robots on flexible cables, addressing unknown dynamics and disturbances.

Findings

Achieves reliable tracking performance in simulations

Effectively estimates unknown cable dynamics

Demonstrates robustness against disturbances

Abstract

In this paper, we present an online adaptive robust control framework for underactuated brachiating robots traversing flexible cables. Since the dynamic model of a flexible body is unknown in practice, we propose an indirect adaptive estimation scheme to approximate the unknown dynamic effects of the flexible cable as an external force with parametric uncertainties. A boundary layer-based sliding mode control is then designed to compensate for the residual unmodeled dynamics and time-varying disturbances, in which the control gain is updated by an auxiliary direct adaptive control mechanism. Stability analysis and derivation of adaptation laws are carried out through a Lyapunov approach, which formally guarantees the stability and tracking performance of the robot-cable system. Simulation experiments and comparison with a baseline controller show that the combined direct-indirect adaptive robust control framework achieves reliable tracking performance and adaptive system identification, enabling the robot to traverse flexible cables in the presence of unmodeled dynamics, parametric uncertainties and unstructured disturbances.