Design, Control and Energy Minimization Strategies for the ARL Monopod

Abstract

We have built a planar one-legged robot (the ARL Monopod) to study the design, control and energetics of autonomous dynamically stable legged machines. Our 15kg robot is actuated by two low power 80W DC electric motors, yet it operates in a stable and robust fashion up to a running speed of 4.3km/hr (1.2m/s). Both design and control of our machine borrow heavily from Raibert's work whose robots use much more powerful hydraulic actuators. Despite our comparatively low power available for actuation, only the hopping height controller had to be modified to achieve stable running. In order to improve energetic efficiency we introduced a scalar "locomotion time" variable, which maps one locomotion cycle onto a fixed interval, independent of operating conditions. This locomotion time has allowed the implementation of a reference trajectory for flight phase leg angle tracking. We have performed a detailed energetic analysis of robot running for the ARL Monopod in order to determine how its ef...