Tool Center Point

The point on the end-of-arm tool that actually does the work; the robot aims and moves this point, not the mounting flange.

The tool center point (TCP) is a reference point defined on the end-of-arm tool, together with its own coordinate frame — for example, the midpoint between a gripper's two fingertips, the tip of a welding torch, or the center of a suction cup. The arm itself only knows where its flange (the end mounting face) is, so once a tool is attached, a fixed transform from the flange to the TCP (a position plus an orientation) must be configured before the controller can send the tool tip to a target pose, move it in a straight line, or rotate it about a point. Get the TCP wrong and the tool offsets as a whole — most noticeably when rotating about a point — so the TCP is usually recalibrated whenever the tool changes. In embodied AI, whether a dataset's or a policy's 'end-effector pose' refers to the flange or the TCP varies by convention and needs to be unified across cross-embodiment training; Franka's libfranka library, for instance, reports the flange frame and the end-effector (EE) frame separately.

ExampleAfter mounting a parallel gripper on the arm, set the TCP at the midpoint between the two fingertips: commanding the robot to rotate about the TCP then keeps the fingertip position fixed while only changing the gripper's orientation. If the TCP were still left at the flange, the fingertips would instead swing out along an arc.

Also called

TCP, Tool Frame, TCP Point

Related

End Effector · Tool Flange · End-Effector Pose · Homogeneous Transformation Matrix · Hand-Eye Calibration · Absolute Positioning Accuracy

Sources

RoboDK Documentation: General Tips (Tool Center Point)
libfranka robot_state.h (F_T_EE, O_T_EE)