What is a User frame?

• A. A coordinate system that remains stationary relative to the world frame.
• B. A coordinate system attached to the robot base that never moves.
• C. A coordinate system aligned to a fixture or workpiece that is translated and/or rotated with respect to the world frame.
• D. A coordinate system attached to the end of the robot that moves with the arm.

Answer: (C)

A user frame is a coordinate system you define to attach to a fixture or workpiece. This lets you express positions and orientations of tasks relative to the part you’re working with, making it easier to plan motions like picking, drilling, or assembly. This frame moves with the object because it is tied to the fixture, so as the part is translated or rotated, the user frame follows it relative to the world frame. By contrast, the world frame is fixed in the environment, the robot base frame is attached to the robot and does not move, and the end-effector frame is attached to the robot’s hand or tool tip and moves with the arm. Thus, the described concept matches a frame defined on the fixture or workpiece that moves with it.