1. A method for determining a stability measure of a legged robot, the method comprising calculating the rate of change of the robot's centroidal angular momentum ({dot over (H)} G ) in accordance with the equation: 
 {dot over (H)} G =GP×R, wherein G represents a location of a center of mass of the robot, R represents a resultant ground reaction force acting upon the robot, P represents a location of a center of pressure of the resultant ground reaction force, GP represents a vector from G to P, and × represents a vector product operation.