Research On Bit Pattern Interpolation Algorithm Of Complex Curves And Surfaces

Advanced manufacturing technology represents the developing direction of the manufacturing technology, while the CNC technology is the most important technology in the family of advanced manufacturing technologies and equipments. The CNC technology and equipments are the strategic materials in many developed countries. The interpolating technology of complex curves and surfaces is the key technology in the CNC technologies and it's mastered only by a few big companies in the world, such as FANUC and Siemens. Nowadays, most of the high performance CNC systems of our country are imported from foreign countries. The kernel technologies in these systems are closed to the users and it is not helpful for the CNC development of our country.This dissertation is supported by Natural Science Foundation of Jiangsu Province (Code: BK2003005). The principle and implementation of the bit pattern algorithm are studied in the dissertation, and many key technical problems are solved. One type of algorithm of bit pattern interpolation (BPI) of complex curves and surfaces is developed. A new way for the development of the CNC technology has independent intellectual property right in China. The mainly research achievements are shown as following.The principle of the BPI algorithm is researched and the algorithm is implemented by using interrupt function of controller. A velocity control algorithm of the BPI is presented. An error-controllable BPI data-generating algorithm is proposed. Firstly, the tool-path was built according to the key points of the machining curve. Parametric cubic spline was used to fit these key points. Then, the tool-path was dispersed into many line segments. To ensure the calculation accuracy, the equation reflecting the relation between the maximum allowable error and the segment number was deduced. The discrete ratio was based on the equation. At last, the BPI data was generated according to these line segments.The front questions of the curve machining technology and pen cutting algorithm of sculptured surface are discussed and the problems of the machining technology of complex curves and surfaces are analyzed. Furthermore, some key problems are pointed out. To solve these problems, the BPI algorithm is introduced into the pen cutting technology. Aiming at the problem of surface intersection operation in the pen cutting, the pen cutting is divided into two conditions, micro local-area cutting and general local-area cutting. For micro local-area cutting, the starting point of the objective driving curve is mapped to the machining area and the bit pattern data is generated according to the objective driving curves. The machining is finished based on the starting point and the bit pattern data. For general local-area cutting, the objective driving curve is dispersed into many short segments in the error range. Then, the endpoints of these short segments are mapped to the machining area, and the bit pattern data is generated according to the connecting lines of the mapping points. Furthermore, the BPI algorithm is introduced into the surface global processing technology. Iso-parametric method is used to make the tool-path plan firstly. Then, the bit pattern data of the iso-parametric curves is generated and the machining is performed according to the bit pattern data. A whole three-coordinate interpolating module of complex curves and surfaces is built according to above research.The problem about tool locating is also studied in the dissertation. Two terms of the pen cutting are researched and different tool locating strategies are made according to the terms. A tool-axis vector generating algorithm is proposed. The algorithm can ensure the continuity and smoothness of the global tool-axis vector. The BPI algorithm is introduced into the five-axis pen cutting, and a data generating algorithm of the five-axis BPI is presented. A whole five-axis interpolating module of complex curves and surfaces is built according to above research.The nonlinear error controlling problem in the five-axis machining is studied. The reason of the nonlinear error production is analyzed and the existing problems of the general error control methods are pointed out. The RTCP method is introduced into the five-axis BPI. By comparing the RTCP method with the general error control method, a conclusion is drawn that the RTCP method can not only control the nonlinear error effectively but also avoid the problem of repeated modification of processing program.