Radical Robots: BigDog

Picture this; you’re in the woods going on an easy hike. You have a backpack with snacks and a water bottle and maybe an emergency first aid kit, just in case. All of a sudden a big loping creature comes climbing up the hill after you. It’s the size of a deer and moves like a dog that prances. It’s Boston Dynamics BigDog and it’s carrying an enormous amount of bags and materials.

BigDog is a dynamically stable quadruped robot that was created in 2005 by Boston Dynamics with Foster Miller, the NASA Jet Propulsion Laboratory, and the Harvard University Concord Field Station. It can maneuver up and down hills, in leaves, in snow, and even on ice. An onboard computer receives input from sensors and manages locomotion, navigation, and balance. It was funded by the Defense Advanced Research Projects Agency (DARPA) to act as a mechanical pack mule in terrain that is too rough for traditional vehicles with wheels or treads. Big Dog’s four legs function with the help of four low-friction hydraulic cylinder actuators that power the legs and allow it to tackle all kinds of tricky terrain. The legs use a variety of sensors, including joint position and ground contact along with a laser gyroscope and a stereo vision system. There are around 50 sensors keeping BigDog in motion. They measure the attitude and acceleration of the body, motion and force of joint actuators as well as engine speed, temperature, and hydraulic pressure inside the robot’s internal engine. BigDog is powered by a two-stroke, one-cylinder, 15-HP go-kart engine operating at over 9,000 RPM. The engine drives a hydraulic pump, which in turn drives the hydraulic leg actuators. Each leg has four actuators (two for the hip joint, and one each for the knee and ankle joints), for a total of 16. Each actuator unit consists of a hydraulic cylinder, servovalve, position sensor, and force sensor.

What an awesome robot in the real world! This robot is able to carry all kinds of instruments and baggage so that people have more accessibility in varied terrains and climates. What would you use your BigDog robot for? Where would you go? If you think about what comes in your FIRST Tech Challenge MATRIX or TETRIX kit, what would you need to make a robot that walks instead of rolls?