J.A. Yagüe

Development and calibration of self-centring probes for assessing geometrical errors of machines

A new type of probe for calibration, verification or interim checking of machine tools as well as robots or parallel-kinematics machine tools is presented in this paper. This probe is part of a ball-artefact-based method to assess the geometrical errors of linear and angular axes in a quick and reliable way. The discussion about the best design concept for the self-centring probe, the mathematical modelling and design process of one of those concepts and the development of three different prototypes are shown. Different sensors and design options were developed to optimize the size and cost of the probe. The calibration of the probe prototypes by way of a kinematically coupled reference device to allow on-machine tests is shown. The uncertainties obtained were around 1 µm for one of the prototypes and below 5 µm for the other two. Finally, results of a geometrical verification of a machine tool are demonstrated, with values similar to the ones achieved using other methods, such as laser interferometry. Compared to those other methods, the new technique was shown to be less time consuming.

Calibration, non-geometric error modelling and correction methods for Articulated Arm Coordinate Measuring Machines

The different accuracy and repeatability requirements of articulated Arm Coordinate Measuring Machines (AACMM) and robots make it necessary to consider different kinematic parameters identification techniques covering the characteristic operational parameters in each case. This paper presents a data capture technique for subsequent identification of an AACMM kinematic model parameters, using nominal data reached by a ball bar and a kinematic coupling. Also this paper addresses the performance evaluation of the algorithm and objective functions used, based on a new approach, including terms regarding measurement accuracy and repeatability.

Traceability In The Calibration Of Low Cost Opto‐Electronic Sensors For Measuring 2D Displacement

The utilization of 2D non‐contact sensors for measuring displacements is a more and more used alternative for the development of several degrees of freedom precision systems. Inside this group of sensors, optoelectronic devices such as CCDs (Charge‐Coupled Devices) or PSDs (Position Sensitive Detectors) are included. PSDs are an adequate option when the economical cost needs to be decreased. Nevertheless, characterizing and adequately correcting the error of those sensors is needed in order to achieve the expected accuracy. A possible technique to carry out this kind of calibration is based on the use of a 2D‐Cross‐Grid Encoder as a reference. However, the calibration of those Cross‐Grid Encoders itself is being done by the manufacturers in a separate way in each of the two axes by comparing the displacement in each of them to a laser interferometer and only along their central lines. Therefore, there are a big number of errors that cannot be determined by that traditional calibration. In this paper a 2D ...