BigDog

BigDog is a dynamically stable quadruped robot created in 2005 by Boston Dynamics with Foster-Miller, the NASA Jet Propulsion Laboratory, and the Harvard University Concord Field Station. BigDog is 3 ft long, stands 2.5 ft tall, and weighs 240 lb, about the size of a small mule. It is capable of traversing difficult terrain, running at 4 mph, carrying 340 lb, and climbing a 35 degree incline. Locomotion is controlled by an onboard computer that receives input from the robot's various sensors. Navigation and balance are also managed by the control system.

History
BigDog is funded by the Defense Advanced Research Projects Agency (DARPA) in the hopes that it will be able to serve as a robotic pack mule to accompany soldiers in terrain too rough for conventional vehicles. Instead of wheels or treads, BigDog uses four legs for movement, allowing it to move across surfaces that would defeat wheels. The legs contain a variety of sensors, including joint position and ground contact. BigDog also features a laser gyroscope and a stereo vision system.

BigDog's walking pattern is controlled through four legs, each equipped with four low-friction hydraulic cylinder actuators that power the joints. "The BigDog robot, labelled as a military robot mule, has subsequently proven its potential worth in its ability to reduce load and remove that burden from a soldier's back."

The BigDog project was headed by Dr. Martin Buehler, who, in 2012, received the Joseph F. Engelberger Award award from the Robotics Industries Association for the work. Dr. Buehler, while previously a professor at McGill University, headed the robotics lab there, developing four-legged walking and running robots.

Built onto the actuators are sensors for joint position and force, and movement is ultimately controlled through an onboard computer which manages the sensors.

Approximately 50 sensors are located on BigDog. These 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. Low-level control, such as position and force of the joints, and high-level control such as velocity and altitude during locomotion, are both controlled through the onboard computer.

BigDog was featured in episodes of Web Junk 20 and Hungry Beast, and in articles in New Scientist, Popular Science, Popular Mechanics, and The Wall Street Journal.

On March 18, 2008, Boston Dynamics released video footage of a new generation of BigDog known as AlphaDog. The footage shows BigDog's ability to walk on icy terrain and recover its balance when kicked from the side.

The refined equivalent has been designed by Boston Dynamics to exceed the BigDog in terms of capabilities and use to dismounted soldiers.

In February 2012, DARPA, which has continued to support the programme, carried out the first outdoor exercise on the latest variation of the LS3 with it successfully demonstrating its full capabilities during a planned hike encompassing tough terrain.

Following the success, an 18-month plan has been unveiled, due to start the summer of 2012, which will see DARPA complete the overall development of the system and refine its key capabilities, ensuring its worth to dismounted warfighters before it is rolled out to squads operating in theatre. The BigDog must be able to demonstrate its ability to complete a 20 mi trek within 24 hours without refuelling while carrying a load of 400 lbs, whereas a refinement of its vision sensors will also be conducted.

At the end of February 2013, Boston Dynamics released video footage of a modified BigDog with an arm. The arm can pick up objects and throw them. The robot is relying on its legs and torso to help power the motions of the arm. The news writer supposed it can lift weighs in the 50 pounds (23 kg) range.

Hardware
Big Dog 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.

Onboard computing power is a ruggedized PC/104 board stack with a Pentium 4 class computer running QNX.