Self-alignment of on-board measurement sensors for robot kinematic calibration

Faced with methods of data acquisition based on systems for external measurement of the pose of a robot, the use of on-board measurement systems and restrictions based on gauge objects or geometric primitives simplifies and reduces robot calibration costs. Because these are inertial measurement systems, it is necessary to accurately establish the relationship between the reference frame of the sensor and the robotʹs global reference frame to be able to use the acquired data later to identify kinematic parameters. This paper presents a technique for aligning the reference frames of measurement sensors mounted on the hand of a robot during the acquisition of nominal and actual data for calibration. This technique permits obtaining data from a gauge object with known geometry in the global reference frame of the robot while retaining the accuracy of the measurement system. It is easily generalized to any contact or non-contact measuring system mounted on a robot and can be used also with external high-range measurement systems based on the capture of points of a moving reflector. It also can be used in measurement systems with on-board sensors, using the robot as a positioning element.