Which elements are typically calibrated in robot calibration?

• A. Joint encoder offsets
• B. Link lengths
• C. Tool center point
• D. All of the above

Answer: (D)

Calibrating a robot’s kinematic model targets correcting the main sources of systematic pose errors that come from how the robot really measures and constructs its geometry. Each parameter has a clear effect on end-effector accuracy, so addressing all of them together gives the most reliable model.

Joint encoder offsets are the differences between what the encoder reports and the actual joint angle. If these offsets aren’t corrected, every computed pose starts from a biased angle, and all subsequent positions drift accordingly. Fixing these offsets aligns the robot’s joint-angle readings with reality, which is essential for precise motion.

Link lengths reflect the true physical distances between joints. Manufacturing tolerances, assembly imperfections, or wear can make these distances different from the nominal values. Updating the link lengths changes the geometric backbone of the robot model, so the inferred positions along a planned path match what the robot actually passes through.

The tool center point (TCP) is the exact reference point on the end effector used to define poses. If the TCP is off from where the control system assumes it to be, the end-effector’s reported position and orientation will be biased relative to the intended tool tip. Calibrating the TCP ensures that commands translate to the correct tool location and orientation in the workpiece or environment.

Because all three aspects influence how commanded motions map to real-world positions and orientations, calibration typically includes joint encoder offsets, link lengths, and the tool center point. Calibrating only some elements leaves others contributing to residual errors, so addressing all three yields the most accurate robot model.