In the present application of Coordinate Measuring Machines (CMMs), generally only the estimated value of the measured quantity can be computed while its corresponding measurement uncertainty can not. It is well known that a result without its uncertainty is incomplete. However, uncertainty evaluation has always been one difficult issue in application of CMM because error sources causing measurement uncertainty of CMM are very complex. Based on Geometrical Product Specifications (GPS), the three measurement strategies of CMM application, i.e. conventional measurement, substitution measurement and compensation measurement strategies, are studied in this paper. For each measurement strategy, the uncertainty sources are analyzed, and the corresponding task-oriented uncertainty evaluation model is established. In this paper, the hole diameter measurement of one workpiece is taken as an example. The uncertainty is evaluated respectively according to the three different strategies, and the results are compared. The comparison result shows that the influence of different measurement strategy on measurement result is different, the maximum difference is about 2 times, and the accuracy of measurement can be improved through selecting proper measurement strategy for specific measurement task.
The measuring force of a micro/nano probe is an important factor affecting the probe measurement accuracy. The strength of the force largely depends on the nature of the suspension structure. How to improve the flexibility of the suspension structure is a difficult issue. To tackle the problem, this paper will put forwards an integrated suspension structure, which composed of three evenly spaced elastic hinges. Each elastic hinge has two beams, one of which is used to as the support. In measurement, the maximum displacement is occurred at the intersection of the two beams. In this paper, the flexibility of the suspension structure and probe measuring capability related to the elastic hinge's size and material are investigated based on theoretical modeling and simulation. The research result is significant to reduce the probe measuring force and improve its sensitivity.
The paper is enlightened by the traditional combination verification method, provides a new detection way to CMM
which is the combination of space one-dimension balls combination. It uses one-dimension balls instead of the standard
ruler of the tradition combination verification method, adopts special researched detection equipment to CMM making
one-dimension balls to three-dimension. The CMM processes the space random line with symmetry associating and
comparing measurement method, and then uses the least-squares method to the measured data to obtain the measurement
error of the space line, consequently realizes the measurement accuracy detection of the CMM.