Tool path generation and error control method for multi-axis NC machining of spatial cam

In this paper, based on the homogeneous coordinate transformation and conjugate surface theory, a tool path generation method is developed for generating spatial cam in order to establish the interface between the design and manufacture of this class of product. The mathematical error (chordal deviation) between the design and manufacture surface has been analysed and used as a basis for selecting the tool path control point. Moreover, the developed tool path generation method is verified through a cutting simulation software with solid model. It is also verified through the trial cut with model materials on a five-axis numerical controlled machine. The results show that the mathematical error of the cam surface can be controlled within given tolerance by the proposed method.     

A method of tool path compensation for repeated machining process

This paper proposes a software method to compensate for the contour error in repeated machining process. In the proposed method, the profile of the first machined part is measured by a coordinate measuring machine. Based on the measured data, the tool path is modified by a compensation algorithm, and then, is represented by a series of linear segments. Finally, the compensated tool path is fed to the CNC machine tool for the machining of subsequent parts. Mathematical analysis and experimental evaluation are presented in this paper.     

Development of a Five-axis Milling Tool Path Generation Algorithm based on Faceted Models

This paper describes the development of a 5-axis milling tool path generation algorithm based on faceted or tessellated models. In a first step, the developed algorithm optimises the tool inclination angle for maximal material removal rate in each cutter contact point. This is obtained by matching the tool profile of a flat end cutter with a temporary spline representing the curvature of the part surface in the tool contact point. In a second step, the elimination of gouging between the tool and the surface and a smooth behaviour of the tool inclination angle along the tool path is obtained by a combination of tool inclination angle adaptation and tool lifting along the normal vector. Finally, the paper describes some experimental results.     

大型构件计算机控制液压同步提升系统的实时控制算法

大型构件液压同步提升技术是近年发展起来的一项新颖的建筑施工安装技术。它已经在我国的许多重大工程建设中得到成功的应用。本文介绍一种计算实时ＰＩＤ控制算法一双限幅ＰＩＤ算法,试验和实际结果表明：与一般ＰＩＤ算法相比,静态误差更小,更适合工程实用。     

数控5轴龙门机床的虚拟加工系统开发

针对新研制的龙门移动式数控5轴车铣复合机床XKA2780结构复杂,已有成熟虚拟加工系统灵活性差,必须要系统厂家深度开发方能实现的问题,文章提出了一种灵活可控的虚拟加工方法,首先基于大型工程软件开发平台ACIS/HOOPS,采用组件结构树的建模方法,建立了机床各组件之间的运动学关系并开发了相应的运动控制模型;其次通过扫描包络技术研究了刀具扫描包络体生成算法;然后以刀具轨迹为引导,将生成的刀具扫描包络体与工件进行布尔运算,实现了仿真环境中工件的虚拟切削;最后,通过对典型航天零部件的加工代码仿真和现场机床切削试验,验证系统的可靠性。实践结果表明,该系统可以对加工代码进行有效验证,且运动控制可兼容各种构型数控机床。     

Sliding mode cutting force regulator for turning processes

Continuous sliding mode control is applied to turning processes for cutting force regulation. The motivation of the use of the slide mode control scheme is to solve the nonlinearity problem caused by the feedrate override command element in the commercial CNC machine tool. When the adaptive control algorithm is applied to the commercial CNC machine tool, it is one of the practical methods that the programmed feedrate is overridden after the control algorithm is carried out. However, most CNC lathe manufacturers offer limited number of data bits for feedrate override, thus resulting in nonlinear behavior of the machine tools. Such nonlinearity brings ‘quantized' or discrete effect so that the optimal feedrate is rounded off before being fed into the CNC system. To compensate for this problem, continuous sliding mode control is applied. Simulation and experimental results are presented in comparison with those obtained from applying adaptive control which is a widely used approach in cutting force regulation. Adaptive control loses its effectiveness in the presence of nonlinearity since it generally requires linear parametrization of the control law or the system dynamics. Experiments are conducted under various machining conditions, subject to changes in spindle speed, material of work-piece, and type of machining process. The suggested slide mode controller shows smoother cutting force fluctuation, which cannot be achieved by the conventional adaptive controller. The experimental set-up reflects the emphasis on the practicality of the sliding mode controller. In order to avoid the use of a dynamometer in the course of measuring the cutting force, the indirect cutting force measuring system is used by means of feed drive servo-motor current sensing.     

基于Speedgoat的dVRK机械臂控制系统开发

为提高dVRK外科机器人控制系统的快速响应性和控制实时性,开发一种基于实时目标机Speedgoat的机器人实时控制系统。通过搭建宿主机-目标机机器人控制平台,设计UDP Real Time通信模型块,建立宿主机、目标机的运行模型,实现对机器人的实时控制。结果表明：实时控制系统可准确地完成对dVRK机器人的数据采集和相关控制算法验证;搭建的Speedgoat实时控制平台具有在线调参、实时仿真、目标代码快速原型化、仿真精度高、可靠性好等优点,大大缩短了dVRK机器人控制算法的研制周期。     

自由曲面参数线加工算法

从工程实际应用出发,提出了一种适合裁剪NURBS曲面加工基于参数线的刀轨生成算法。在曲面的参数线上规划刀位规划,将曲面用三角片离散逼近,利用刀具曲面与三角的几何相关性进行了干涉检查及刀位修正。实践表明,算法速度快、稳定性好。     

Virtual Computer Numerical Control System

This paper presents a comprehensive virtual simulation model for CNC systems. The Virtual CNC (VCNC) has a modular architecture, allowing a real CNC to be prototyped quickly from standard library functions for feed drive models, feedback devices, axis control laws, and trajectory interpolation. Additional CNC modules can easily be prototyped and integrated to the VCNC by the user. Various application examples are presented which include the prediction of contour errors, auto-tuning of feed drive controllers, toolpath and feed modification for improved cornering, and rapid identification of closed loop drive dynamics. Detailed experimental verification is presented for each algorithm.     

纵切数控车床交互式CAPP系统的设计

针对纵切数控车床工艺设计灵活多变、工艺人员经验不可替代的特点,设计了纵切数控车床交互式CAPP系统.工艺设计中,用户决定加工方法的选择、加工顺序的安排、刀具的选择和加工参数的确定这些经验性强、灵活多变的部分;系统则提供辅助的工具方便用户决策,并根据用户输入的参数,调用系统内部的算法自动地生成刀具轨迹.交互式CAPP系统将人的经验和计算机的计算能力结合起来,具有很好的实用性和灵活性.     

基于CompactRIO的电液比例控制系统研究

针对电液比例控制元件检测试验台的项目要求,结合有关科学研究性实验(控制策略生成与验证),设计一套基于CompactRIO的电液比例控制系统,并以美国NI公司的LabVIEW虚拟仪器软件为开发平台,构建控制回路,设计了PID以及模糊自适应PID控制策略。该系统能就控制策略的生成与验证进行仿真研究,同时具有良好的人机交互界面,方便用户操作。仿真结果显示,利用LabVIEW+NI CompactRIO模式成功实现了电液比例控制系统的控制目的。     

冷带轧机液压AGC系统的MAC-PID串级控制

冷带轧机液压AGC系统的控制精度决定了冷轧带钢的成品精度,而目前现场的液压AGC系统主要采用PID控制。针对液压AGC系统,在其中的液压压下伺服系统中应用模型算法控制(MAC),同液压AGC系统厚度外环的PID控制相结合,形成MAC-PID串级控制。同时,进行了轧制试验,试验结果表明:所采用的MAC-PID串级控制算法实时性较好且易于实现,提高了成品带钢的板厚精度。     

基于ARM9的齿轮加工数控系统的研究

为了提高齿轮的加工精度、嵌入自主研发的控制算法,提出一种基于嵌入式系统的齿轮加工数控系统。对系统进行了硬件设计和软件设计,并对系统进行了功能模块划分;分析插齿刀加工运动轨迹以及插齿刀和工件的运动关系,计算出关键点坐标值,构建出插齿加工自动编程的数学模型,并实现了插齿加工自动编程功能模块。研究内容为今后齿轮数控加工控制精度的提高提供了参考。     

A real-time NURBS surface interpolator for precision three-axis CNC machining

Due to the fact that the cutting occurs around the cutter contact (CC) point, the efficiency and quality of CNC machining can be improved significantly if the CC velocity along the surface is kept costant. Conventional approaches to machining mainly maintain a constant cutter location (CL) velocity, so that the CC velocity along the surface is often not constant and usually results in non-uniform machining and unsatisfactory quality. To overcome this difficulty, this paper presents a novel NURBS surface interpolator that is capable of real-time generation of CL motion command for ball-end milling of NURBS surfaces and maintaining a constant CC velocity along the CC path and its intervals. For performance evaluation, a three-axis servomechanism driven by three servomotors is controlled to track segments represented by NURBS surfaces. Experimental results verify the effectiveness of the proposed method.     

泵控容积调速系统的实时控制研究

本文在分析液压泵控容积调速系统特性的基础上，提出以单片机ＭＣＳ－５１为控制单元，以步进电机为执行元件的闭环实时控制系统的方案，介绍了系统实时控制的实现方法和系统实际运行的实验结果。     

Optimization of CNC isoscallop free form surface machining using a genetic algorithm

Isoscallop machining with edge-based master cutter path (MCP) essentially ensures uniformity of surface roughness over entire surface of part but may not necessarily ensure minimization of machining time. In the present work, it has been shown that there is a provision for minimizing machining time while implementing Isoscallop machining, by optimizing the orientation of the primary or Master Cutter path (MCP) through application of a GA. The results indicate a substantial reduction in total machining time for the proposed approach compared to those obtained through previously reported cutter path generation strategies.     

一种新型的个性化假肢快速成型系统

经过对假肢接受腔CAD模型数据的分析和处理,通过特定的算法,计算出加工刀位点,然后转换成控制脉冲数据,最后控制系统驱动刀具和模型合成螺旋运动,加工假肢接受腔阳模。该系统提高了假肢接受腔一次制作成功率,降低了成本。     

自由曲面平头立铣刀五轴数控加工轨迹的计算方法

提出了一种在参数坐标系下自适应步长和行距的计算方法 ,该算法考虑了不同刀具接触点处的曲率差异 ,在满足加工精度和粗糙度的前提下 ,又能有效地提高加工效率。该算法适合加工汽车车身模具等曲率变化大的曲面。文中还给出了刀位计算公式。     

金刚石砂轮的成形方法

为了满足单件小批量地生产用于加工硬质合金螺纹刀具的金属基金刚石成形砂轮的需求,在原有的电火花加工金属基金刚石成形砂轮的方法上提出一种新的成形金刚石砂轮的加工方法。采用实时检测、实时控制和两轴联动全闭环数控系统单刀加工成形石墨电极,再用电火花加工方法加工出成形金刚石砂轮。并通过实验验证了成形石墨电极的加工精度。此方法能够满足单件小批量生产成形金刚石砂轮的需求。     

3自由度移动机器人的模糊逻辑控制方法研究

3自由度移动机器人可以实现平面上的自由运动,具有很高的灵活性和机动性。针对具有两个可操舵驱动轮的3自由度移动机器人的轨迹跟踪问题,利用模糊控制技术设计了路径跟踪控制器,实现了移动机器人的位置和方位的独立跟踪,同时提高了跟踪控制的实时性。最后通过仿真验证了算法的可行性和有效性。