Analysis of the energy flow on quadruped robot having a flexible trunk joint

A problem in legged robots compared with wheeled robots is energy loss. A legged robot continues running at equal speed, if total mechanical energy is conserved. However, the faster the average speed is, the larger the energy loss is. A legged robot walks at a regular speed when input energy and energy loss are balanced. If the energy loss per step could be reduced by analyzing the energy outflow from the robot phase by phase, the resulting balanced speed would be faster. The possible energy loss involves viscosity, friction and impact with the ground, negative work (to control the joint angles) of the actuators, and so on. The purpose of this study is to establish a control method for quadruped robots, by which the walking speed is greatest with limited input energy. We aim at clarifying the mechanism of the flow of mechanical energy: translational and rotational kinetic energy of each link, elastic potential energy of each elastic element, and gravitational potential energy of each link.