An Iterative Algorithm for Wrist-Mounted Robotic Sensor Calibration with or without External Orientation Measurement

Abstract

An iterative algorithm for calibration of wrist-mounted robotic sensors is presented. The sensor-wrist calibration can be performed by solving a system of homogeneous transformation equations of the form A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> X = XB <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> , where X is the unknown sensor position relative to the robot wrist, A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> is the ith robot motion, and B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> is the ith sensor motion [1-4]. Unlike existing approaches, the algorithm presented here solves kinematic parameters of X in one stage, thus eliminating error propagations and improving noise sensitivities. Moreover, with the iterative algorithm, the parameters of X are observable even when the rotation part of B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> is unknown. This is important in practice since position is easier to measure than orientation. Comparative simulation studies show that the accuracy performance of the iterative algorithm is, in general, better than that of noniterative two-stage algorithms, regardless whether the orientation part of B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> is used. The approach presented in this paper also has wide applications for wrist-mounted tool calibration.