Modeling and identification of errors of coordinate measuring arms with the use of a metrological model

The Coordinate Measuring Arms (CMAs) are modern, mobile measuring systems using rotary joints in their kinematic. Their chief characteristic is redundancy. Therefore, it is particularly important to develop procedures for the CMAs allowing for the assessment of the accuracy of measurements. Such set of procedures would have to be well-defined and unified, allowing for the use of the substitution method and a number of other measurement strategies, or even running some producer-specific tests. However, in the present situation, most of these tasks are difficult and time-consuming. In response to this problem, the simulation systems of evaluation of the accuracy of performed measurements in an on-line mode (the so called Virtual Articuled Arm Coordinate Measuring Machines), as well as systems determining the error compensation matrix (referred to as Articulated Arm Computer Aided Accuracy) are being developed, and are gaining more and more attention. In order to become fully functional, both of these systems require a precise identification of all the parameters describing each part of the CMA, as well as identifying all the possible operational errors of the device. This paper proposes a description of a CMA with the use of kinematic parameters.

► Kinetic description of CMA is consistent with description of open kinetic chain. ► Determination of CMA geometric parameters allows creation of software correction matrix. ► Two conceptions of geometric errors determination were developed and compared. ► New method of CMA geometric errors determination based on the error of reproducibility of the measuring point were developed.