Degrees of Freedom (DOF)

Degrees of freedom describes the number of independent parameters needed to specify the configuration of a mechanical system. A robot arm with six revolute joints has 6 DOF — enough to position and orient its end-effector arbitrarily within its reachable workspace (barring singularities). A 7-DOF arm adds one redundant joint that allows null-space optimization for obstacle avoidance or comfort poses. Human arms have roughly 7 DOF at the shoulder-elbow-wrist chain, making 7-DOF robots natural choices for anthropomorphic manipulation. Mobile bases add 2–3 DOF; full humanoids exceed 30 DOF.