Degrees of freedom

The number of independent ways a robot, or one of its joints, can move.

• Each degree is one independent motion, usually one motorised joint. Placing an object anywhere in space takes 6: three for position, three for orientation.
• That is why industrial arms have 6; a seventh adds redundancy, letting the elbow swing around an obstacle while the hand stays put.
• A human hand has roughly 20–27; robot hands range from a few to over 20, and each one adds a motor, weight, wiring and a failure point.
• Spec sheets can mislead: some joints are mechanically coupled to move together, so the stated count can exceed the number of motors.