Robust Adaptive Control of Fully Constrained Cable-Driven Serial Manipulator with Multi-Segment Cables Using Cable Tension Sensor Measurements.

Ya’Nan Lou,Pengkun Quan,Haoyu Lin,Dongbo Wei,Shichun Di

doi:10.3390/s21051623

Abstract

The structure of the cable-driven serial manipulator (CDSM) is more complex than that of the cable-driven parallel manipulator (CDPM), resulting in higher model complexity and stronger structural and parametric uncertainties. These drawbacks challenge the stable trajectory-tracking control of a CDSM. To circumvent these drawbacks, this paper proposes a robust adaptive controller for an n-degree-of-freedom (DOF) CDSM actuated by m cables. First, two high-level controllers are designed to track the joint trajectory under two scenarios, namely known and unknown upper bounds of uncertainties. The controllers include an adaptive feedforward term based on inverse dynamics and a robust control term compensating for the uncertainties. Second, the independence of control gains from the upper bound of uncertainties and the inclusion of the joint viscous friction coefficient into the dynamic parameter vector are realised. Then, a low-level controller is designed for the task of tracking the cable tension trajectory. The system stability is analysed using the Lyapunov method. Finally, the validity and effectiveness of the proposed controllers are verified by experimenting with a three-DOF six-cable CDSM. In addition, a comparative experiment with the classical proportional–integral–derivative (PID) controller is carried out.

Highlights

The iniinitial position of the cable-driven serial manipulator (CDSM) in the circular sub-path was set at q(0) = q (0) T+
Having the same experiment conditions as the previous study, the high-level controller is replaced with a well-tuned PID controller, which is commonly used in the literature for the tracking of the desired joint position
This study proposes a robust adaptive controller for stable tracking of the joint position and cable tension trajectories in a CDSM

Summary

Introduction

Cable-driven serial manipulators (CDSMs) are a series of connected rigid bodies driven by cables instead of actuators which are positioned at each joint [1]. CDSMs possess low stiffness, low weight, low moving mass and a large reachable workspace. Such robots can be applied in medical rehabilitation [2], assembly in a complex narrow cavity [3,4], automatic charging in electric vehicles [5], nuclear reactors [6], etc. This paper studies the control of a fully constrained n-degreeof-freedom (DOF) CDSM, the actuation cable number m of which is at least n + 1, i.e., m ≥ n + 1 [7,8]

Objectives

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Conclusion