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Boston Dynamics, Inc./DARPAs PETMAN Robot Climbs Stairs


Fri, 13 Apr 2012 Ā«permalinkĀ»

The novelty behind PETMAN/ATLAS1 is the way he uses his upper body to assist his lower body dynamics. As humans, this is a natural mode of coordination; if you start to fall over or if you trip, you can naturally use your arms and torso to help stabilize yourself. This works by changing the location your body’s center of mass so that its projection2 along gravity gets moved closer to where your feet are (or are going to be), allowing you to catch yourself. As you move your arms and body around, you change the shape and orientation across which your mass is distributed and so your CoM moves around. You can also use your environment to help out with this, pushing off walls or grabbing on to things.

As natural as this is for humans, it’s a relatively complex concept to translate in to control systems heuristics and algorithms. Notice that as PETMAN climbs the stairs, he uses a single arm pushing against a wall and bent knees to center the projection of his center of mass to the appropriate support polygon.

BDI’s PETMAN/ATLAS is the robotics platform that will be used as the base platform for the newest DARPA Grand Challenge

[CoM]: Center of Mass [BDI]: Boston Dynamics, Inc. *[PETMAN]: Protection Ensemble Test Mannequin.


  1. PETMAN stands for Protection Ensemble Test Mannequin. He is one of the first robots to move with human dynamics, and he was designed to test chemical protection suits.

  2. The center of mass is a point in space, and it is found by averaging the mass of an object over the shape and density of an object to determine a single point where it can be assumed the entire mass of the object is situated. Its projection along gravity is the point in space on the ground that is perfectly straight down from this point in space. Situating the CoM inside the support polygon helps stability.