This paper furnishes the theoretical basis to perform the calibration of one or more ultra-high-precision industrial robots operating in the same workspace. We propose a new calibration procedure that keeps in account the factors that lower the robot accuracy at nanometer scale. To validate this approach, we present the practical case of the calibration of a two industrial robots system. Finally, we propose nano-indentation as an alternative method to evaluate the final accuracy reached by the system after calibration.

While dealing with sub-micrometer precision robots, thermal expansion is the most significant source of inaccuracy. Thermal variations in the environment, in the robot parts and in the frame change the robot geometry, lowering the robot precision. In this article we propose a strategy to model and compensate such effects. The thermal behavior of a 3 DOF (Degree(s)-of-freedom) parallel robot has been studied using a high-precision measuring system. A model of the robot thermal behavior has been built and implemented in the controller. By using it, thermal deformations are compensated in real-time and an absolute accuracy of ±71 nm has been reached.