Fault-Tolerant Control for System Availability and Continuous Operation in Heavy-Duty Wheeled Mobile Robots
Mehdi Heydari Shahna, Pauli Mustalahti, Jouni Mattila
TL;DR
The paper tackles fault-tolerant control for heavy-duty wheeled mobile robots (HD-WMRs) operating in challenging environments where sensor and actuator faults can jeopardize safety and operation. It introduces a model-free hierarchical fault accommodation (MFHCA) framework that uses adaptive laws and inverse kinematics to drive four independently actuated wheels and steering mechanisms, achieving exponential stability despite faults. Key contributions include a fault-inclusive motion-dynamics representation, an adaptive fault-detection/isolation mechanism, and driving/steering valve control strategies validated on a 6,500-kg hydraulic HD-WMR, showing improved tracking and robustness over existing controllers. The work has practical impact by enabling safer, continuous operation of HD-WMRs in rough terrain and under heavy loads, with potential extensions to other platforms and fault types.
Abstract
When the control system in a heavy-duty wheeled mobile robot (HD-WMR) malfunctions, deviations from ideal motion occur, significantly heightening the risks of off-road instability and costly damage. To meet the demands for safety, reliability, and controllability in HD-WMRs, the control system must tolerate faults to a certain extent, ensuring continuous operation. To this end, this paper introduces a model-free hierarchical control with fault accommodation (MFHCA) framework designed to address sensor and actuator faults in hydraulically powered HD-WMRs with independently controlled wheels. To begin, a novel mathematical representation of the motion dynamics of HD-WMRs, incorporating both sensor and actuator fault modes, is investigated. Subsequently, the MFHCA framework is proposed to manage all wheels under various fault modes, ensuring that each wheel tracks the reference driving velocities and steering angles, which are inverse kinematically mapped from the angular and linear velocities commanded in the HD-WMR's base frame. To do so, this framework generates appropriate power efforts in independently valve-regulated wheels to accommodate the adaptively isolated faults, thereby ensuring exponential stability. The experimental analysis of a 6,500-kg hydraulic-powered HD-WMR under various fault modes and rough terrains demonstrates the validity of the MFHCA framework.