Step-Climbing Tactics Using a Mobile Robot Pushing a Hand Cart

The present paper describes step-climbing tactics using a wheeled robot and a hand cart that has a hand brake. The robot has two arms that are used to hold or push the handle of the cart and a lower extendable wheel mechanism that can push against the bottom of the cart. Some of the manipulator joints are controlled passively when moving over the step. To lift the front wheels of the cart, the robot holds the handle steady and pushes against the bottom of the cart using the extendable wheel mechanism. This action is similar to that performed by a human. The robot then pushes the entire cart forward so that the front wheels of the cart are above the step. When the rear wheels of the cart have climbed the step, the upper-arm links of the manipulators are pressed against the robot chest to allow the robot to push the cart. When the cart has fully climbed the step, the robot then uses the cart to climb the step. The present paper describes the details of the robot system, and theoretical analyses were performed to determine the requirement of masses and the centers of gravity of both vehicles to lift the cart. Experiments were also carried out in which the robot was controlled using an intranet connection, and the results demonstrated the effectiveness of the proposed method.