Robot walks on all four legs and carries a heavy load

Industrial Robot

ISSN: 0143-991x

Article publication date: 17 August 2012



Bloss, R. (2012), "Robot walks on all four legs and carries a heavy load", Industrial Robot, Vol. 39 No. 5.



Emerald Group Publishing Limited

Copyright © 2012, Emerald Group Publishing Limited

Robot walks on all four legs and carries a heavy load

Article Type: Mini features From: Industrial Robot: An International Journal, Volume 39, Issue 5

Soldiers in battle have always faced the dual tasks of carrying heavy loads as well as facing the enemy. DARPA, the US Defense Advanced Research Project Agency, in team work with a contractor, Boston Dynamics, have developed the Legged Squad Support System (LS3 Alpha Dog) four legged robot to help foot soldiers (Figure 2).

The goal was to create a dual function robot which can “tag along” or operate completely autonomous as a walking load carrier. The LS3 Alpha Dog will follow a foot solider or can be sent off to make a delivery all on its own. The robot can carry up to a 181 kg load and can “walk” up to 32 km in 24 hours before needing to be refueled. It has the ability to walk over rough terrain such as might be found in battle situations.

 Figure 2 LS3 Alpha Dog carrying its load while walking alone over a rocky
path in the woods

Figure 2 LS3 Alpha Dog carrying its load while walking alone over a rocky path in the woods

The robot is powered with a gasoline engine. The engine also charges the onboard batteries that provide energy for controls and sensors as well as provide an energy reservoir for recharging handheld devices the patrol foot soldiers may be carrying such as laptop computers, two way radios, and night vision glasses and such.

Sensors at the head of the robot provide the follow along skill and other sensors are on the watch for obstacles such as rocks, trees and other terrain obstacles and maintain balance. For autonomous operation a GPS system can be programmed to guide the LS3 to the desired delivery location.

The movement system provides balance control, bounce when needed and the leg bending and advancement motion. Each leg uses four hydraulic actuators that power the joints as well as the fifth degree of freedom. A hydraulic pump running off the engine provides the oil flow/pressure. A heat exchanger keeps the oil at the correct operating temperature.

The hydraulic actuators enable the robot to crawl, walk, trot, run or jump as needed. In crawl, one leg at a time is moved. In trot, diagonal legs are lifted and moved at the same time. The fastest gait is 3.1 meters per second. The robot has jumped about 1.1 meters high in tests.

The control system coordinates the kinematics and ground reaction forces. It distributes the load to maintain balance. The sophisticated control algorithms allow the robot to walk on incline and decline to 60° from horizontal.

Long-term goals for the development program include giving the robot the ability to re-right itself should it fall over and to make the gasoline engine quieter. For more information on the LS3 and to watch videos of the robot in action please visit:

Richard BlossAssociate Editor, Industrial Robot

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