Coordinated control for five-leg one-arm robots

Abstract

A working six-legged robot which can switch three modes of locomotion and manipulation by using some legs as arms is under development: six-leg mode and two kinds of four-leg two-arm modes, where the robot holds and manipulates an object with two arms. Attaching hands to the legs enables five-leg one-arm mode; the robot grasps a small object with one hand and manipulates the object with one arm, while walking stably with five legs. Because the arm has three DOF, the robot needs to move its body with the five legs in order to control the pose of the hand. The present paper proposes a coordinated control method of five legs and one arm to manipulate five-DOF pose of the hand. The robot stands on the five legs. From the desired velocity and angular velocity of the hand, the joint velocities of the arm and the velocity and angular velocity of the body are determined. From the determined body velocity and angular velocity, the joint velocities of the five legs are obtained. These joint velocities are commanded to the robot. If at least one of the five support legs reaches the limit of its movable area, the robot stops the arm and body temporarily. Then the five legs step to the center of their movable areas. After the five legs finish stepping, the robot resumes the control of the hand. Experiments of moving the hand along straight lines show the validity of the proposed method.