Control of an omnidirectional mobile robot with wheels connected by passive sliding joints

Abstract

To solve problems of conventional mobile robots, such as constrained mobility due to nonholonomic wheels or complicated structure due to specialized wheels, we propose a novel omnidirectional mobile robot named slidable-wheeled omnidirectional mobile robot (SWOM). SWOM has three conventional wheels connected to the main body by passive sliding joints, which enable the main body to make omnidirectional movement in spite of the nonholonomic constraints on the wheels. Thus, SWOM achieves both superb mobility and simple structure. However, its behavior is described as a nonlinear system with nonholonomic constraints, which has difficulty with control because this type of system does not have a general design method for a stabilizing controller. This study aims to develop a controller for SWOM using state feedback linearization. This paper presents the following achievements: An exactly linearized state equation is derived using feedback and coordinate transformation based on the kinematics of SWOM. The unwanted singular configurations of the system are discussed and a control strategy to avoid them is proposed. Then, a stabilizing controller that enables SWOM to reach a designated position and orientation is designed. Through a numerical simulation and an experiment using a SWOM prototype, the effectiveness of the developed control system was verified.