An Omnidirectional Transportation System With High Terrain Adaptability and Flexible Configurations Using Multiple Nonholonomic Mobile Robots

Multi-robot cooperative transportation systems (MRCTSs) hold great potential in industrial material transport, where they need to be omnidirectional, highly flexible, adaptable to various terrains, and cost-effective. This letter presents an industrial MRCTS that employs a novel composite connector, consisting of a passive revolute joint and a gasbag, to link the robots and the payload. An angular sensor is used in the revolute joint to provide feedback control on the robot's orientation. We also introduce a simplified and cost-effective cooperative strategy that treats the robots as steering wheels (SWs) and the entire transportation system as a single robot with multiple SWs. The cooperative strategy for transporting payloads only necessitates handling robots to measure their heading, and the information provided to handling robots solely consists of the control velocities of the payload. Besides, we provide kinematics controllers for the entire system and individual robots and successfully perform three kinds of physical handling experiments. Experimental results demonstrate that the system can smoothly shuttle between flat and sloping roads without any midway stopping and possess highly flexible configurations. Besides, the system shows omnidirectional mobility, despite using nonholonomic mobile robots.