How is geometric accuracy evaluated in robotic systems?

• A. Use metrology tests across poses to compare actual vs nominal positions, calibrate as needed, and assess sources of error like backlash or flex
• B. Use metrology tests at a single pose only
• C. Only rely on visual inspection
• D. Only measure end-effector temperature

Answer: (A)

Geometric accuracy is about how closely the robot’s actual pose matches its intended pose across the workspace. To evaluate it, use metrology tests across a representative set of poses and orientations, measuring the end-effector’s true position and orientation with a high-precision reference instrument and comparing those values to the robot’s nominal predictions. This produces error data that shows how far off the robot is at different configurations, which you can use to calibrate the system—adjusting kinematic parameters, joint offsets, and encoder biases or applying compensation. By checking many poses, you uncover pose-dependent errors and understand how different factors contribute to the inaccuracy.

Common error sources you’ll uncover include backlash or play in gears and joints, structural flex under load, thermal expansion, and other forms of mechanical or control-induced deviation. Visual inspection or single-pose checks don’t capture how accuracy varies throughout the range of motion, and measuring temperature alone doesn’t quantify geometric positioning accuracy (though temperature can influence it). So the best approach is broad metrology across poses, followed by calibration to mitigate identified errors.