Glossary · Robotics and control
Open-loop control
Also called open loop, closed-loop control, closed loop, feedback control
Sending fixed commands without looking at what happens. The opposite of feedback (closed-loop) control, which corrects itself from what it measures.
A closed-loop controller measures the state, compares it with what it wants, and acts on the difference, again and again: a thermostat, a servo, a trained policy. An open-loop controller just sends its commands: a toaster’s timer, or a fixed sequence of motor signals played out regardless of where the arm actually is.
Open loop is no good for staying balanced, but it is a clean experiment: by forcing the commands, you see what the body itself can do, with the controller’s choices taken out.
In this project
In Muscles instead of motors, to tell whether the muscle fighter’s slow punches were a lack of strength or a choice, the jab’s muscles were forced fully on from the stance, open loop, with the rest of the body still under the policy. The fist reached 8.6 m/s with the opposing muscles off and 3.0 m/s with them at half excitation: the body is strong enough, and the half-on opposing muscles brake it.