A Study of NURBS Interpolation Algorithm with Limited Chord Error for EDM The traditional EDM interpolation for NURBS curve is to divide the curve into several straight line segments and arc segments for linear and arc interpolation. It takes a long time to generate a large number of G codes, and difficult to control the machining error. In this paper, an interpolation algorithm based on NURBS curve for EDM is proposed which mainly includes two parts: Firstly, using the NURBS interpolation with the chord error control model as a realtime preprocessing to generate a series of small interpolation line segments and store in the loop buffer. Secondly, interpolate the line segment in the loop buffer with the fine interpolation algorithm. Experiment results validate that the EDM interpolation algorithm based on NURBS curve can control the machining error more effectively and improve the machining efficiency greatly.

Alignment of an Unmarked Deformable Sheet Like Object Based on NURBS Fitting In this paper, we proposed a method to realize automatic labeling task of a flexible sheet like object. It is a demonstration to the similar operations widely adopted in industrial production line such as those in flexible printed circuits assembly. In these operations, it needs to precisely position a specific part within a deformable sheet to a predefined position. In many applications involving such operations, the usage of artificial markers are not allowed and the target may lack enough features for tracking. Thus 3D position of the alignment reference has to be estimated from its contour. The task of aligning an unmarked paper sheet considered in this paper well demonstrates these situations. In this paper, Nonuniform rational BSplines (NURBS) fitting is utilized for tracking the shape variation of the paper. It is proved that for an unstretchable sheet like object, the fitted NURBS plane can be used in the way of servo control for regulating the shape. It provides a simple way to track the featureless points described with the paper undeformed generally as a sketch. The advantage of the proposed method is verified by successful alignment experiment in which a certain line defined on an undeformed paper sheet is aligned to the predefined position on a box.