Which statement about DOF is NOT true?

• A. Point space is the area or points that a robot can possibly reach within a defined space
• B. DOF refers to the number of independent movements a robot can perform
• C. A revolute joint contributes one DOF
• D. Cartesian coordinates represent a robot's position in space

Answer: (A)

Degrees of freedom measure how many independent motions a mechanism can perform, i.e., how many independent coordinates you need to specify the end-effector’s pose (position and orientation). Each joint that can move adds one DOF; for a revolute joint, that means one independent rotation about its axis.

The statement about point space is describing the reachable workspace—the set of points the robot can reach within its joint limits. DOF, by contrast, counts independent motions, not the size of the area the robot can reach. The other statements align with how DOF is defined: the number of independent movements a robot can perform; a revolute joint contributes one DOF; and Cartesian coordinates can describe the robot’s position in space (x, y, z), with orientation described separately.