Motion pattern generation based on the free vibration for an explosive increase of the kinetic energy in the robot end-link during swing motion

Abstract

The purpose of our research is to improve robot motion ability without depending on only actuator power by effectively exploiting the dynamic properties of a robot. In this paper, we focused on swing motion (e.g., throwing or kicking motion). The prime purpose in swing motion is to increase the kinetic energy of the end-link (e.g., hand or foot). In this paper, using a multi-link planar robot, we proposed a method to generate a robot motion for an explosive increase of the kinetic energy in the robot end-link. Humans increase the kinetic energy of the end-link by exploiting the dynamic properties during swing motion. The kinetic energy of the end-link increases because large energy produced by strong muscles in the center side of the body is transferred toward the end side. We constructed mathematical models to explain this mechanical phenomenon on the basis of the free vibration. Furthermore, we proposed a method to generate a robot motion for an explosive increase of the kinetic energy in the robot end-link using the models. The results of simulation experiments showed that the kinetic energy of the end-link increases because large energy produced by actuators in the center side of the robot is transferred toward the end side. Furthermore, the robot motion generated by our method is similar to a trajectory optimized based on energetic cost. Then, we proposed a method to generate a robot motion considering the torque limits of actuators by revising the method mentioned above. The results of simulation experiments showed that torques required by actuators are reduced by using the revised method.