TABLE OF CONTENTS The objective of geometric calibration is to identify the exact values of the geometric parameters, which play a role in the calculation of the geometric models of the robot, in order to improve its static accuracy. The nominal values of these parameters are known and generally provided by the manufacturer. It is then a matter of identifying the distance between the nominal values and the real values [HOL 89], [KHA 02].
The location of the end-effector in the world frame R f is given by (see section 1.2.3.1):
with:
Z, E: transformation matrices defined in section 1.2.3.1;
0 T n: transformation matrix of the robot.
Based on relation [1.42], we distinguish three types of parameters: the geometric parameters of the robot required to calculate the matrix 0 T n, the parameters defining matrix Z and those defining matrix E.
Matrix j?1 T j defined by equation [1.3] is based on ( ? j, d j, ? j r j). In the case where two consecutive axes j ?1 and j are parallel, the choice of x j?1 is not unique, which leads to an arbitrary choice of the position of x j?1. When an error takes place such that z j?1 and z j are not rigorously parallel, the error ?r j?1 for parameter r j?1
