Capture point

When you trip on a curb, you throw a foot forward to the one place that stops you. That place is your capture point. Step short of it and you stumble on; step past it and you lurch back.

Robot engineers worked out a way to calculate this spot from how fast and in which direction the robot’s body is moving. The robot’s balance software uses it to decide when and where to step.

In a push-test video, a robot that lands one clean step and stops dead has hit its capture point. A robot that shuffles several steps has missed it and is correcting.