Real-Time Control of Anthropomorphic Robot Which Moves While Working by Arms (Motion Control in Sagittal Plane)

A real-time control method of an anthropomorphic robot which moves with its legs while doing a given task by its arm is proposed. The robot has two legs and one arm because the motion in sagittal plane is discussed; the unknown external force acts on the arm tip. The arm controls its tip by impedance control so that the tip can always follow the desired position or external force prescribed by the given task. The legs change two control modes according to the current arm tip position and external force: 1) When the external force is small or the arm tip moves in narrow space, the robot keeps double support state and controls its shoulder in order to keep the robot stable against the force and to make the arm easy to do the task. 2) If the large force acts or the arm tip must be moved in wide range, the robot steps in order to prevent it from tumbling, thus recovering the robot's stability and the arm tip's manipulability shifted in new double support state. Furthermore, the robot can cope with the sudden change in the external force and the moving direction of the arm tip. The effectiveness and usefulness of the proposed method are ascertained by computer simulation and experiment.