The Deleting Datum Technology In The Evaluation Of Roundness Error

With the rapid development of science and technology, the evaluation of roundness error of round work piece is more and more important. How ever working on a large number of samples is often time-consuming, it is necessary to research on deleting datum technology. Based on investigation of deleting datum technology existing, further research on convex hull algorithm and a-hull algorithm is done in this paper. And working on two groups of simulating data indicates that the deleting datum technology proposed in this paper has a higher efficiency.For convex hull algorithm, a phenomenon discovered by Wang Li, that while the nominal radius is being decreased the deleting datum efficiency is being improved, is proved mathematicly in this paper. And the algorithm of decreasing nominal radius, as a new deleting datum algorithm, is analysed in detail, and its feasibility range is discussed. Besides, an improved algorithm is proposed. Forα-hull algorithms, it is proposed that usingα-hull in the evaluation of minimum circumscribed circle and maximum inscribed circle. For minimum zone circle evaluation, some improvement, based on the algothms proposed by Olivier Devillers and Zhang Yong, are made. The improvement is that decreasing the radius of the outerα-hull in the precondition that the radius ofα-hull is not smaller than the radius of outer containing circle of minimum zone, and that increasing the radius of the innerα-hull in the precondition that the radius ofα-hull is not bigger than the radius of inner containing circle of minimum zone. And at last it is proved by experiment that the improved algorithm are more effective.