Research On Software Protection And Interpolation Algorithms For Cnc System

Computer numerical control systems, which denote as CNC systems, have drawn considerably attentions in recent years. The function and performance of CNC system determine the effectiveness of machining, thus greatly influence the development of manufacturing systems in our nation. As a core technology of advanced manufacturing, CNC system copyright protection is of great value on protection of our intellectual and commercial property. And the research on interpolation algorithms for CNC system greatly improves effectiveness and efficiency. Thus, CNC systems which adopt our research results can better meet the needs of high-efficiency and high-quality machining.According to our project, software protection schemes, interpolation method, velocity profile generation approach and five-axis linear interpolation for CNC system has been proposed and discussed in this dissertation.According to copyright protection of CNC system, we proposed and implemented a software protection system, and designed two computational schemes to implement the system. The first signature scheme uses symmetric encryption, asymmetric encryption and hash functions; the second signcryption scheme adopts Shamir Secret Sharing Scheme, hash functions, Lagrange interpolation, and so on. The proposed system can meet the need of CNC copyright protection according to security analysis and anti-attack analysis. And the signcryption scheme has been applied to our developed CNC system. Moreover, a signcryption scheme to ensure network security is introduced, which has many advantages: signcryption and de-signcryption both in parallel, any suitable encryption and signature schemes could be used, very weak security requirement of the adopted algorithms, and message redundancy is greatly reduced. Therefore, the proposition could be more applicable especially when used in long-message signcryption.An important issue is to balance productivity and motion accuracy in the development of CNC system, since the demand for greater productivity requires the system to speed up machining processes to enhance work efficiency, while motion accuracy may be degraded. A variety of on-going research is focused on the analysis of methods to decrease the time spent on machining processes while maintaining or improving the quality of surface. The most significant areas are interpolation algorithms and velocity profile generation approaches for numerical control machining. In order to pursue motion precision and to improve working efficiency, a quintic spline interpolation method and a velocity profile generation approach with optimal look-ahead for CNC system are proposed. The applied interpolation method adopts quintic spline and derivatives generation approach for discrete points by using quartic polynomial, which can better meet the needs of high-accuracy machining. Meanwhile, the addressed velocity profile generation approach for motion planning alleviates the shortages of traditional S-curve acceleration and deceleration control algorithm, while reducing the operation time by proper connections of successive short segments and appropriate settings of corner velocity where the adjacent segments cannot meet the requirements of linking. Finally, a five-axis linear interpolation algorithm is introduced and implemented. The proposed approach can achieve five-axis coordinated movements without taking the risk of overshoot and impact. Experiment results have verified the effectiveness and efficiency of these approaches and they have been applied to our newly developed CNC system.