Coupled fractional-order sliding mode control and obstacle avoidance of a four-wheeled steerable mobile robot

Yuanlong Xie; Xiaolong Zhang; Wei Meng; Shiqi Zheng; Liquan Jiang; Jie Meng; Shuting Wang

doi:10.1016/j.isatra.2020.08.025

Coupled fractional-order sliding mode control and obstacle avoidance of a four-wheeled steerable mobile robot

ISA Trans. 2021 Feb:108:282-294. doi: 10.1016/j.isatra.2020.08.025. Epub 2020 Aug 21.

Authors

Yuanlong Xie¹, Xiaolong Zhang¹, Wei Meng², Shiqi Zheng³, Liquan Jiang¹, Jie Meng¹, Shuting Wang⁴

Affiliations

¹ School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, China.
² School of Information Engineering, Wuhan University of Technology, Wuhan, China; School of Electronic and Electrical Engineering, University of Leeds, Leeds, United Kingdom.
³ School of Automation, China University of Geosciences, Wuhan, China; Hubei key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, China.
⁴ School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, China. Electronic address: wangst@hust.edu.cn.

PMID: 32863054
DOI: 10.1016/j.isatra.2020.08.025

Abstract

Recently, four-wheeled steerable mobile robots (FSMR) have attracted increasing attention in industrial fields, however the collision-free trajectory tracking control is still challenging in dynamic environments. This paper studies a new coupled fractional-order sliding mode control (CFSMC) and obstacle avoidance scheme, which has superior capacities of providing more control flexibilities and achieving high-accuracy. Instead of exploring traditional integer-order solutions, novel fractional-order sliding surfaces are proposed to handle the nonlinear interconnected states in a coupled structure. To accomplish non-oscillating avoidance of both stationary and moving entities within an uncertain workspace, a modified near-time-optimal potential function is subsequently presented with improved efficiency and reduced collision-resolving distances. By utilizing fuzzy rules, proper adaption gains of the reaching laws are designed to degenerate the effect of undesired chattering. The asymptotic stability and convergence can be guaranteed for the resultant closed-loop system. Three experiments are implemented on a real-time FSMR system. The results validate the reliability of the presented CFSMC scheme in terms of significantly mitigated following errors, faster disturbance rejection and smooth transition as compared to conventional methods.

Keywords: Coupled fractional-order sliding mode control; Four-wheeled steerable mobile robot; Near-time-optimal potential function; Obstacle avoidance.