Calibration of an articulated CMM using stochastic approximations

Abstract

A coordinate measuring machine (CMM) is meant to digitise the spatial locations of points and feed the resulting measurements to a CAD system for storing and processing. For reliable utilisation of a CMM, a calibration procedure is often undertaken to eliminate the inaccuracies which result from manufacturing, assembly and installation errors. In this paper, an Immersion digitizer coordinate measuring machine (IDCMM) has been calibrated using an accurately manufactured master cuboid fixture. This CMM has been designed as an articulated manipulator to enhance its dexterity and versatility. As such, the calibration problem is tackled with the aid of a kinematic model similar to those employed for the analysis of serial robots. In addition, a stochastic-based optimisation technique is used to identify the parameters of the kinematic model in order for the accurate performance to be achieved. The experimental results demonstrate the effectiveness of this method, whereby the measuring accuracy has been improved considerably.

Testing coordinate measuring arms with a geometric feature-based gauge:in situfield trials

“…The kinematics of a CMA has been analysed using the Denavit-Hartenberg convention and a virtual simulation model has been built in order to evaluate the accuracy of measurements. Some of these studies pay attention not only to the kinematic parameters of the CMA but also to its dynamic behaviour (torsion and deflection deformations), performing FEM analysis or proposing statistical models for measurement uncertainty (the Monte Carlo method) in conjunction with the geometric model of the CMA [16,17]. These recent studies are beginning to take into account the distortion of CMA joints under the combined action of gravity and the force exerted by the operator.…”

Methodology for the assessment of measuring uncertainties of articulated arm coordinate measuring machines

“…They have also introduced the influence of temperature and have established a correction model based on a physical model of dependency of the geometry parameters on temperature [14]. Sultan [15] developed a calibration process based on a kinematic model whose parameters are identified by approximation resulting from a random disruption. Sladeck et al [16] tackle the problem of theoretical modelling of the error induced by the articulated measuring arms.…”