Measuring and Estimating Rotary Joint Axes of an Articulated Robot

The aim of this article is to chronicle a novel methodology for measuring and estimating rotary joint axes of an articulated robot. The key contribution of the proposed methodology is a practical way of estimating rotary joint axes of an articulated robot by taking static position measurements of every rotary joint, so that the estimated rotary joint axes reflect the real characteristics of the actual robot. Furthermore, the proposed methodology enables an advanced calibration of robot kinematic parameters for a better motion performance. The metrology requires a laser tracker for taking static position measurements. The proposed methodology is intended for articulated robots with serially linked rotary joints. To make the basic concepts easier to understand, the study uses a lower-pair kinematic chain with three serially linked rotary joints. The basic concepts can be extended and applied to higher degree-of-freedom articulated robots. To validate the research outcomes, this article proceeds with a validation experiment that demonstrates the use of the proposed methodology with empirical data produced by a metrology simulation experiment. The results of the validation experiment indicate that the proposed methodology is capable of measuring and estimating rotary joint axes of an articulated manipulator even in the presence of typical sensor noises.