Conversion of Elastic Energy Stored in the Legs of a Hexapod Robot into Propulsive Force

Abstract

The conversion of elastic energy due to ground reaction force into propulsive force can help increase the locomotion speed of a legged robot. Many legged robots inspired by animals have been developed, which utilize the elasticity of their legs to increase the efficiency of locomotion. An example is RHex, a hexapod robot that has C-shaped legs. These robots are designed using the spring loaded inverted pendulum (SLIP) model. In contrast, we proposed a new leg design (i.e., D-shaped leg) and an optimization method in which the speed can be increased by kicking the ground strongly in the opposite direction of locomotion due to the elastic force accumulated in the legs. An experiment with a hexapod robot demonstrated that the walking speed could be increased by up to 89% compared to the speed obtained by C-shaped legs. This result can be applied to the design of hands, grippers, and robot bodies to store external force in the flexible body, introduce new functions, and improve performance.