【作者】 余森楠；

【导师】 王永青；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2010， 硕士

【摘要】 参数曲线曲面插补运算和加减速控制模块是高性能CNC系统研究开发的重要内容之一。自由曲线曲面理论在CAD/CAM技术上的应用以及具有自由曲线曲面特征零件的数控加工对CNC系统插补技术提出了更高的要求。研究开发支持曲线曲面实时插补加工功能的CNC系统,对于提高CNC系统整体性能,促进CAD/CAM/CNC技术的集成意义重大。本文针对自由曲线曲面CNC系统插补技术应用编写了NURBS曲线曲面类,并提出了一种基于三次样条函数的柔性加减速算法,通过设定最大加速度和加加速度条件,获得直至二阶可导的速度曲线,可以实现平滑无突变的速度控制目标。改进了预估-校正参数计算方法,提出了基于一阶泰勒展开式的预估-迭代修正法,有效地减小截断误差对速度的影响,改善了曲线插补过程中的速度特性。提出了一种曲线曲率自适应参数插补算法,通过引入离线插补预处理过程,检测曲线上速度敏感区域,按照柔性加减速控制规律对该区域进行速度平滑处理,使之在满足弦高差和机床加速能力约束的前提下,速度平稳变化。本文对常用的曲面刀具路径生成方法进行了分析研究,提出了一种在线刀具路径生成的算法,该算法以等参数线法为原型,并根据国内外相关研究前沿对其做了改进,在结合曲率自适应参数插补算法的基础上,能够获得可靠稳定的连续路径生成及实时曲线插补性能。最后,利用VC++和Matlab软件对曲率自适应参数插补和曲面刀具路径生成算法进行了仿真,并根据仿真结果对参数插补的误差和速度控制效果进行了分析验证,对曲面加工刀具路径生成算法的有效性和可靠性进行了分析说明。仿真结果说明了算法的正确性和有效性,对于提高CNC系统的曲面路径处理能力和曲线插补能力具有重要意义。更多还原

【Abstract】 Parametric curves and surfaces interpolaiton and velocity control are very important in the CNC system modules. More requirements for the CNC interpolation have been brought by application of free-form curves and surfaces theory in CAD/CAM and NC machining of components with characteristics of free-form curves and surfaces.The research on the development of a kind of CNC system which supports real-time interpolation for free-form curves and surfaces is of great significance on the improvement of the overall performance of the CNC system and the integration of the CAD/CAM/CNC technique.NURBS curve and surface class is developed for the application of the curve and surface interpolation technique of the CNC system. A flexible acceleration and deceleration algorithm based on the cubic spline function is proposed in this dissertation for curve and surface interpolation. By setting the terms of maximum acceleration and jerk, even the second derivative velocity curve can be obtained and the control objective that the velocity is in a smooth profile without jerk limit can be achieved.The predictor-corrector(预估-校正)parameter calculation method is bettered, and the predictor-iterative correction method is proposed based on the first-order Taylor expansion, which effectively reduces the impact of truncation error on the velocity, and improves the speed characteristics during the process of curve interpolation. A curvature adaptive parametric interpolation algorithm is presented in this thesis. The feed-rate sensitive areas on the curves are detected through offline interpolation preprocessing, where the velocity is planned in accordance with the flexible acceleration and deceleration control method, so that the velocity profile can be smooth as long as it can satisfy the chord error and meet the constraint of machine acceleration.In this paper, the commonly used tool path generating method for parametric surfaces is analyzed, and then an on-line tool path generation algorithm is presented, which takes iso-parametric as the prototype, and has made further improvements about it according to the current research at home and abroad. Based on its combination with the curvature adaptive parametric interpolation algorithm, reliable and continuous path generation and real-time interpolation properties can be gained. At last, the curvature adaptive parametric interpolation and tool path generation for NURBS surfaces are simulated using VC++ and Matlab, and then according to the simulation results, the velocity control effect and parametric interpolation error are analyzed and verified, also the validity and reliability of the tool path generation algorithm for surfaces are specified. The simulation results show that the algorithm is correct and valid, and has important significance for improving the parametric surface path processing ability and the curve interpolation ability of CNC system.更多还原