A Real-time Look-ahead Algorithm Of NURBS Parameter Interpolation

CNC plays an important role in modern equipment manufacturing industry. High speed and high machining accuracy are development trend of CNC system. Interpolation module is the core of the controlling software among the whole numerical control systems, the selection of interpolation algorithm will directly affect the precision and speed of numerical system. The only mathematical method NURBS curve as the definition of industrial products geometry. NURBS interpolation technology can enhance processing precision, surface smoothness and production efficiency, thereby improving performance of numerical system. Parametric interpolation is presently supported by majority of CNC systems because of its various advantages over traditional linear/circular interpolation Hence, it is of great significance for manufacturing industry to have a study towa rds interpolation algorithm.In this paper, the main work and achievements are as follows :(1) This thesis introduces the NURBS curve in its mathematical module, expression form, qualities and related parameters calculation in detail s, and establishing of the NURBS curve mathematical model. By considering the profile error and the feed acceleration limited, secondary Taylor expansion method is used to calculate the next interpolation point. Supplemented by the precision of parameter estimated correction.(2) S shape oriented approach has special advantages in high precision and no rapid change in speed as well as smooth transference. This paper puts forward the approach of pre-interpolation S shape acceleration and deceleration control. Implements the NURBS curve interpolation method of deceleration planning in advance.(3) Based on the advantages of S shape acceleration and deceleration method, a look-head interpolation algorithm for parameter curves is designed. Through dividing look-ahead distance into two parts, sensitive points were analyzed, a continuous velocity and accelerating profile were found out which reduced the acceleration relate problem. This method ensured the feed speed and acceleration transition smoothly.(4) Computer simulation analysis is made towards the given curves by using MATLAB software interpolation algorithm, including morphological analysis of the feed rate, feed acceleration transfinite analysis, chord error and interpolation time. The experimental results are provided to verify the feasibility of the proposed interpolation algorithm.