1. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity June 13, 2006

2. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity There 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.

3. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity 2) The Support Polygon is the “base” of the robot, which is the polygon that is formed by its wheels. RectangleTriangleLine (not too stable)

4. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity For 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.

5. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity The 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.

6. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity Why 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.

7. ©2006 CSUC Institute for Research in Intelligent Systems Center of Gravity Now we can practice this theory with the Egg Tower Activity!