Vertical ladder climbing down motion with internal stress adjustment for a multi-locomotion robot

This paper describes a ladder climbing down motion for a multi-locomotion robot (MLR). Since a closed kinematic chain is formed by robot links and the ladder in the ladder climbing down motion, if there exist redundant position controlled joints, an internal stress would appear due to the position errors (in the environment or in the joint position, ...). The internal stress has no contribution to equilibrate the robot load (weight and inertial force), however it produce greater torsional stress to the robot joint inside the closed chain. A control algorithm so that is proposed to adjust the internal stress. The primary contribution is in improving the working condition and minimizing the total squared torques of robot joints by reducing the additional internal stress. Since the pace gait is fast and flexible for robot climbing down the ladder, it is taken as an example to explain the proposed control method.