TCP: the Tool Center Point
If the robot would not know about tools attached to it, it would be very cumbersome to make precise movements, for example if a fine pencil would be mounted on it. By defining a Tool coordinate system, most often called a Tool Center Point, it is possible to precisely let the robot know of a particularly useful point on the attached tool. This allows for example the tip of a pencil to be defined as the origin of the tool, the robot then being able to navigate in space and bring exactly this point to the surface of a sheet of paper. Most robot controllers provide ways to calibrate the TCP by moving the robot in a specific sequence after which the controller can compute the TCP offset without measuring it.