Static Stability Versus Dynamic Stability · 1/2
Freezing the frame: static stability
A robot is statically stable at a given instant if it could freeze its motion right then and remain balanced without falling, because its center of mass projection is safely within the support polygon at that moment. A statically stable gait maintains this at every instant throughout motion, which means the robot must carefully shift its weight onto the remaining support feet before it ever lifts another one.
This is safe, and it's how some cautious walking robots and many industrial legged platforms move, but it's also slow. Constantly re-centering weight before each lift adds time and energy cost, and it caps how quickly the robot can move since every step requires a stable pause built in before the next.