Experiments with an Electrically Actuated Planar Hopping Robot

We have built a planar one-legged robot to study the design, actuation, control and analysis of autonomous dynamically stable legged robots. Our 15kg robot is powered by two low power 80W DC electric motors, yet it operates in a stable and robust fashion and currently achieves a top running speed of 1.2m/s. Both design and control borrow heavily from Raibert's work whose robots are actuated by powerful hydraulic actuators. Surprisingly, even with our drastically reduced power available for actuation, only the hopping height controller had to be modified to achieve stable running. As a basis for further improvements we introduce a scalar “locomotion time” variable, which maps one locomotion cycle onto a fixed interval, independent of operating conditions. A dynamical model and a computer simulation have been developed which accurately predict the robot's behavior.