The bow leg hopping robot

Abstract

The bow leg hopper is a novel locomotor design with a highly resilient leg that resembles an archer's bow. During flight, a "thrust" actuator adds elastic energy to the leg, which is automatically released during stance to control hopping height. Lateral motion is controlled by directing the leg angle at touchdown, which determines the angle of takeoff or reflection. The leg pivots freely on a hip bearing, and is automatically decoupled from the leg-angle positioner during stance to preclude hip torques that would disturb body attitude. Upright attitude is maintained without active control by allowing the body to "hang" from the hip joint. Preliminary experiments with a planar prototype have demonstrated impressive performance (hopping heights of 50 cm or more), high efficiency (recovers 70% of the energy from one hop to the next) and low power requirements (45 minutes of operation on a small battery pack). Current experiments are focused on developing control and planning schemes to enable locomotion over discrete "stepping stones" and obstacles.