Research Of NURBS Curve Interpolation And Development Of Open-architecture CNC System

The technology of numerical control is a kind of modern automatic control technology, and it is a kind of method of the controls of machine tools which have been realized by using the digital information, is also the most crucial link in modern production technology. The interpolation module is the core of the whole computer numerical control system (CNC) software. The interpolation algorithm directly affects the machining speed and the accuracy of the CNC system. The interpolation with free-formed curve has many advantages. It can get high speed, high efficiency and smoother surfaces. So it's significant to develop interpolation with free-formed curve. NURBS (Non-Uniform Rational B-Spilne) provides a uniform expression of all curves. NURBS interpolation has been a hot research spot and a trend in numerical control filed.According to the requirement of open-architecture CNC system, this paper constructs the open-architecture CNC system based on network by choosing networks and hardware equipments of Rockwell Automation. In this hardware platform of system, some special software are chosen to to achieve NURBS interpolation function. Thereinto, Matlab software is used to interpolation pretreat and optimize. RSLogix 5000 is used to develop motion control program. Supervisory control interface of NC system is created by RSView 32.After introducing the tradition pulse interpolation and the data sampling interpolation, this paper emphasizes to research NURBS interpolation arithmetic. The existing NURBS curve interpolation arithmetic directly has questions which was difficult to eliminate the incremental error and control bow-high and speed. According to the matrix representation of NURBS curve, this paper proposes improved interpolation arithmetic, which changes interpolation cycle, and calculates step-length through the method which dynamic confirm parameter increment. Thus, it can eliminate the incremental error, and properly control the bow-high error to achieve in machining of high accuracy but not change machining speed.At present, people increasingly design the shape of workpiece using NURBS curve. The traditional methods need massive manual programming process and working efficiency is low, it's a hard work and difficult to satisfy the request. Therefore, this paper develops the system using LISP editor to achieve the object-orientation CNC system by consulting the STEP-NC standard. It has many advantages, such quick speed, good quality, shot period of manufacture and so on. In a word, the study of this topic has high engineering value.