Non-kinematic calibration of a six-axis serial robot using planar constraints

• A robot calibration method based on multi-planar constraints is described.
• Simulation confirms that the robot parameters can be identified.
• Experimental validations show that the robot's accuracy is significantly enhanced.
• The experimental data are collected using a touch probe.
• A practical validation approach to evaluate the robot's accuracy is proposed.

This paper describes a non-kinematic calibration method developed to improve the accuracy of a six-axis serial robot, in a specific target workspace, using planar constraints. Simulation confirms that the stiffness of the robot, as well as its kinematic parameters, can be identified. An experimental validation shows that the robot's accuracy inside the target workspace is significantly enhanced by reducing the maximum distance errors from 1.321 mm to 0.274 mm. The experimental data are collected using a precision touch probe, which is mounted on the flange of a FANUC LR Mate 200iC industrial robot, and a high precision 9-in. granite cube. The calibration method makes use of a linear optimization model based on the closed-loop calibration approach using multi-planar constraints. A practical validation approach designed to reliably evaluate the robot's accuracy after calibration is also proposed.