Development of an Agile Omnidirectional Mobile Robot With GRF Compensated Wheel-leg Mechanisms for Human Environments

Abstract

Wheeled mobile robots have been receiving continuous attention in various fields because of their stability, efficiency, and simple mechanisms. However, most of them require significantly larger occupied space than humans and have limited maneuverability in the environment for humans, such as crowded corridors, floor thresholds, ramps, and elevators. This letter presents a new wheel-leg mobile robot that combines the legs for changeable support polygon and mecanum wheels for holonomic motion. The robot has a human-like slim shape with 4 wheel-leg mechanisms, each of which has one 2-DOF leg frame and one mecanum wheel. To allow 2-DOF leg motion while maintaining the orientation of the mecanum wheels, a unique parallel link mechanism was devised. In order to achieve agile motion and impact and vibration absorption capability, a back-drivable high payload compound planetary gear was developed. The ground reaction force (GRF) compensation mechanism in each leg reduces the required payload of the actuators. The letter describes the detailed mechanical design of the robot and the actuators. The effectiveness of the proposed robot was verified in various experiments, fast omnidirectional motion test, a climbing test of a single step, and a motion test in the elevator with people.