DESIGN AND CONTROL OF RANGER: AN ENERGY-EFFICIENT, DYNAMIC WALKING ROBOT

We present the design and control of an energy-efficient, knee-less, essentially planar, four-legged bipedal robot called Ranger. In separate trials, Ranger: 1) walked a 40.5 mile ultra-marathon on a single charge and without human touch, setting a robot distance record; and 2) walked stably at Total Cost Of Transport (TCOT = total energy used per unit weight per unit distance travelled) of 0.19, apparently less than that of any other legged robot to date. Key design features are: a light weight and high strength box body, low-inertia leg design for fast and efficient swing, foot actuation that combines toe-off and ground clearance, a steering mechanism that enables turning of this essentially planar robot, and a low-power modular networked electronics hardware system. The model-based control approach uses a simplified offline trajectory optimization with a reflex-based feedback controller for stabilization. Ranger's reasonable success suggests that these design and control ideas could be extended to the development of an energy-efficient higher degree of freedom, 3-D bipedal robot.