【作者】 陈龙；

【导师】 于东；

【作者基本信息】 中国科学技术大学 ， 计算机应用技术， 2013， 博士

【摘要】 随着装备制造业的不断发展和市场需求的多样化,数控技术进入了前所未有的高速发展阶段。数控技术集计算机,机械,自动化等多项技术于一体,广泛应用于航空航天,汽车,模具等行业。近年来,随着科技的进步和市场需求的扩大,对大型复杂曲面工件的数控加工需求日益迫切。大型复杂曲面工件具有曲率变化剧烈的自由曲面表面,增加了曲面信息提取和分析的难度,并对数控加工提出了更高的要求,使得自由曲面的刀具轨迹规划技术成为数控加工的关键技术之一。自由曲面刀具轨迹规划的目的是得到更高的加工精度,更快的加工速度和更好的工件质量。在现代数控系统中,数控机床无法直接根据数控代码进行加工,必须通过解释器对数控程序进行解释执行,提取相关数据并转化为相应的加工命令来控制机床进行实际工件的加工。所以说,解释器是数控系统的核心模块之一,其解释效率和解释效果对整个数控系统的高效、精确、安全运行有直接影响。针对于此,本文在面向高速加工、高精加工和高表面光洁度加工的自由曲面刀具轨迹规划方法以及数控系统解释器等方面进行深入研究,并取得了以下研究成果：(1)针对刀具轨迹加工精度不足的问题,研究构建一种面向高精度加工的等残余刀具轨迹规划方法,该方法针对精加工及部分工件对加工精度的特殊要求,采用精度优先的加工策略。采用等残余高度法和往复式的走刀方式,得到的刀具轨迹满足加工误差和最大残余高度等约束条件,具有很高的精度。针对当前曲面凹凸性判断过于复杂的问题,提出了一种快速的曲面凹凸性判断方法。在刀具轨迹规划过程中,解决了因偏置刀具轨迹生成点的数量与当前轨迹相同,对当前刀具轨迹过度依赖和加工精度不足的问题。(2)针对刀具轨迹加工速度不足的问题,研究构建一种面向高速加工的螺旋刀具轨迹规划方法,该方法针对粗加工及部分工件对加工效率的特殊要求,采用效率优先的加工策略。该方法生成的所有刀具轨迹点都在自由曲面上,使曲面信息能够得到最大化的保真,有利于得到更加精确的加工曲面；在刀具轨迹规划过程中运用了相应的刀具轨迹平滑技术,对所有刀具轨迹进行平滑处理,可以得到更加平滑的加工表面,同时也有效增大了单条刀具轨迹长度,更好的保证了加工表面的质量；在刀具轨迹规划过程中对自相交现象进行消除,有效提高了加工速度和工件的表面质量。(3)针对刀具轨迹加工表面光洁度不足的问题,研究构建一种面向高表面光洁度加工的平滑刀具轨迹规划方法,该方法针对高表面质量加工和部分工件对加工表面光洁度的特殊要求,采用表面光洁度优先的加工策略。初始轨迹上的每一个刀具切触点都是使刀具姿态角变化率最小的点,可以保证得到的初始刀具轨迹是最光滑的。此外,对偏置刀具轨迹执行平滑算法,保持了相邻轨迹间的一致性,从而改善了由于执行等残余高度法导致的相邻轨迹间的不规则,以生成光顺的刀具加工轨迹,进而得到更平滑的加工表面。最后,考虑并解决了由于刀具轨迹平滑算法的执行而导致的自由曲面边界未被覆盖的问题。(4)针对高性能数控系统对解释器不断增加的需求,在分析数控代码格式的基础上,详细介绍了解释器的基本原理,功能及其与相关模块的调用关系,提出了解释器的结构模型,将整个解释器分为词法分析模块,语法分析模块,加工命令存储结构,加工命令转化模块和错误处理模块五个部分,并详细阐述了各个模块的构建方法。结合自顶向下分析方法,用EBNF来描述了数控代码的文法规则,并对原有文法规则进行修改,消除了数控代码文法的二义性。更多还原

【Abstract】 With the development of the equipment manufacturing industry and the diversification of market demand, the CNC technology went into an unprecedented rapid development. With the integration of computer technology, machinery technology and automation technology, the CNC technology is widely used in the aerospace, automotive, mold and other industries. In recent years, with the advancement of technology and the expansion of market demand, the demand for CNC machining of large and complex curved surfaces urgent increasingly. Large and complex curved parts having a curvature change free curved surface, it increasing the difficulty of surface information extraction and analysis, and put forward higher requirements to CNC machining, so that the sculptured surface of the tool path planning techniques is becoming one of the key technologies of CNC machining. The purposes of sculptured surface tool path planning is higher machining accuracy, faster processing speeds and better quality of the workpiece.In modern numerical control system, CNC machine can not processing directly from the NC code, the interpreter must be used on the NC program interpretarion. The interpreter can extract the relevant data into the corresponding processing command to control the machine for the actual machining of the workpiece. So, the interpreter is one of the core modules of the CNC system, and the efficiency and effectiveness of the interpreter have a direct impact to entire numerical control system.Above all, this paper make a depth study on the sculptured surface tool path planning, interpretater of numerical control system and other aspects, and obtained the following research:(1) With the problem of insufficient accuracy of tool path, a scallop-height high-precision tool path planning method is proposed. The method is for the special requirements of the finishing machining, which use the precision machining strategy. The method uses a reciprocating path pattern, the generated tool path with high precision can meet the constraints of the processing error and maximum residual height. With the problem of the judgment of concave and convex, we propose a fast method for the judgment of surface. In the process of tool path planning, the number of points on offset toolpath and bias tool path is the same, it cause the over-reliance on the current tool path, this problem and the problem of lack of precision is solved.(2) With the problem of insufficient speed of tool path, a high-speed spiral tool path planning method is proposed. The method is for the roughing and the special requirements of some workpiece’s efficiency machining. All the Generated tool path points is on the sculptured surface, which can make the surface information maximize fidelity and is conducive to get more precise machining surface. The use of the tool path smoothing techniques on the tool path planning process can make thetool path length is effectively increases which lead to the smoother surface finishing. Meanwhile, on the tool path planning process, the phenomenon of self-intersection is eliminated which can improve the processing speed and the surface quality.(3) With the problem of insufficient surface smoothness of tool path, a high surface smoothness tool path planning method is proposed. The method use surface quality priority processing strategies is for the high surface quality machining and the special requirements of some workpiece’s surface quality. Every cutter contact point on the initial tool path has the minimum tool attitude angle rate changes, which can ensure the generated tool path is smooth. Meanwhile, the smoothing algorithm for the bias tool path can maintain the consistency between the adjacent tool path, which can improve the irregularities between adjacent tool path and lead to smooth tool path. Finally, the problem is consider and solved:the sculptured surface boundary are not covered because of the implementation of the toolpath smoothing algorithm.(4) With the increasing demand for high-performance CNC interpreter, on the basis of the analysis of NC code format, the basic principles of the interpreter, function and the call module is described in detail. A interpreter structure model is proposed, the entire interpreter is divided into five parts:lexical analysis module, syntax analysis module, processing command storage structure, processing commands module and error handling module, and each module construction method is detaily descripted. With the combination of top-down analysis method, we use EBNF to describe the the NC code grammar rules, and modify the original grammar rules, eliminating the ambiguity of the NC code grammar.更多还原