BigDog has four legs that are articulated like an animal’s, with compliant elements to absorb shock and recycle energy from one step to the next. BigDog is the size of a large dog or small mule.
BigDog's on-board computer controls locomotion, processes sensors, and handles communications with the user. BigDog’s control system keeps it balanced, manages locomotion on a wide variety of terrain, and does navigation. Sensors for locomotion include joint position, joint force, ground contact, ground load, a gyroscope, LIDAR, and a stereo vision system. Other sensors focus on the internal state of BigDog, monitoring the hydraulic pressure, oil temperature, engine functions, battery charge, and others.
BigDog runs at 10 kmh, climbs slopes up to 35 degrees, walks across rubble, climbs muddy hiking trails, walks in snow and water, and carries up to 150kg loads.
Development of the original BigDog robot was funded by DARPA. Work to add a manipulator and do dynamic manipulation was funded by the Army Research Laboratory's RCTA program.