Control of robot using coupled torque between joints

In high speed motion, the coupling inertia torques and nonlinear velocity torques of a robot arm are the major components of the dynamic forces and often cause that one of the motors exceeds its torque limit. The experiment outlined in the paper utilizes `the coupled torques´ to decrease the required torque of the motor. The authors have developed a direct-drive robot arm with 3 degrees of freedom. The inertia matrix and the dynamics of the robot arm are analyzed. The authors put an extra weight on the arm to change the inertia matrix of the robot arm. To evaluate the ability of the robot arm, they introduce an evaluation function, the `general acceleration margin´ (GM) which expresses the remaining acceleration ability of the robot arm. The inertia matrix is optimally designed for the robot arm to have the largest GM. The optimization of the inertia matrix makes the robot arm realize the high speed trajectory