Four-Wheel Independent Steering and Four-Wheel Independent Driving Robot and its Simultaneous Path and Orientation Tracking Control

Abstract

In recent years, road collapse incidents owing to underground cavities have occurred frequently. To investigate underground cavities before accidents occur, periodic cavity inspections are conducted using ground penetrating radar (GPR) equipment. When cavity inspection is performed by humans directly moving a GPR-equipped hand cart in areas inaccessible to vehicles, such as sidewalks, the area that can be inspected simultaneously is limited, often resulting in missed inspections. To address this issue, we developed a robotic system with omnidirectional mobility using a four-wheel independent steering and driving mechanism, primarily aimed at automating sidewalk cavity inspection. Cavity inspection requires path tracking control along the designated survey line; however, conventional path tracking methods are mainly designed for robots with nonholonomic constraints, such as two-wheel independent driving systems, making them unsuitable for omnidirectional mobile robots. In this study, we propose a control method called simultaneous path and orientation tracking control, which considers omnidirectional mobility. The proposed method consists of feedforward control for the target path and orientation, combined with feedback control to correct deviations. By distributing the control inputs into two degrees of freedom for the translational velocity and one degree of freedom for the angular velocity, the position and orientation of the robot can be controlled independently. Several experiments were conducted in a real-world environment to evaluate the reproducibility of the tracking control, demonstrating the effectiveness of the proposed method in terms of path and orientation tracking performance.