Abstract
This paper proposes a new straightforward control method which is applicable to the reaching movement by a three degrees-of-freedom redundant manipulator in the two dimensional vertical plane with the gravitational force. This control law does not include any apparent compensator for the gravity, and not contain the Jacobian matrices. In the formulation of the arm, nonlinear springs and a tendon-driven structure are implemented in the arm according to antagonistic mechanism like the upper limb structure of the human. The proposed controller is designed based on the joint space of the robot, as a result, the singular point on the motion pathway does not appear. Finally, in the simulation of precise positioning control of the end effector, we reveal that the desired trajectories of each joint are all virtual physical quantity, to which the joint is not required to converge through the reaching movement.
