Enhanced Calibration of Robot Tool Centre Point Using Analytical Algorithm

Abstract

This paper introduces an enhanced method to analytically identify an unknown tool centre point (TCP) of standard industrial robots with six degrees of freedom. The method uses a mathematical closed form to determine the position and orientation (pose) of a mounted robot tool frame in relation to the robot flange frame. This unknown pose is represented by a homogeneous transformation that is calculated by performing two robot movements. The position and orientation of the robot is measured after each movement, which leads to an equation of the form , where represents the unknown homogeneous transformation from the robot flange to the TCP. The achievable accuracy in comparison to existing methods is enhanced by using relative movements with orthogonal rotational axes. This ensures optimal error propagation for solving the resulting equation and leads to a very accurate calculation of the unknown transformation. The described method was evaluated and tested on a standard industrial robot. All measurements to determine the position and orientation of the robot tool were done with a laser tracker. A typical application example from the field of automated machining demonstrates the use of the developed method. 