Robotics Academy 2002. All Rights Reserved.

Center of GravityThe RCX is, by far, the heaviest component of your robot. Therefore, it should be well positioned for the robot to have good balance.

GoodBad!

Robotics Academy 2002. All Rights Reserved.

Center of GravityThere are two main concepts in understanding balance.

1) The Center of Gravity (or Center of Mass) is the single point on an object where all of its weight is assumed to be located.

For the RCX, the Center of Gravity can be assumed to be directly in the center of the brick.

Robotics Academy 2002. All Rights Reserved.

Center of Gravity2) The Support Polygon is the “base” of the robot, which is the polygon that is formed by its wheels.

Rectangle Triangle Line (not too stable)

Robotics Academy 2002. All Rights Reserved.

Center of GravityFor the most stable robot, its Center of Gravity should be as close to the center of its Support Polygon as possible.

This robot tips over because the Center of Gravity is outside of the Support Polygon.

Robotics Academy 2002. All Rights Reserved.

Center of GravityThe height of the Center of Gravity also affects balance.

Even though the center of the RCX is within this robot’s Support Polygon, it only takes a tiny push to the side for the Center of Gravity to move outside of the Support Polygon.

Robotics Academy 2002. All Rights Reserved.

Center of GravityWhy is this robot bad? Why is this robot good?

The RCX is high and barely inside the support polygon.

The RCX is low and well centered within the support polygon.