摘要
关节臂式坐标测量机是一种新型非正交坐标测量系统,与传统的正交坐标测量机相比,具有结构简单、体积小、重量轻、测量范围大、操作方便灵活、成本低、可在现场或野外测量等特点,已较广泛地应用于模具设计、零件逆向工程测量、产品质量在线检测、设备装配与维修等领域。然而关节臂式坐标测量机的测量精度与传统的正交坐标测量机相比要低(两者通常相差一至两个数量级),导致其使用范围受到较严重的限制。究其原因,自由度大、关节数目多、空间串联结构等特点,其结构参数的误差在过程中会发生积累和放大,导致其精度不高。另外,采用关节臂式坐标测量机测量小尺寸零件时,其测量空间往往比被测零件大得多,造成测量空间较大的浪费,损失了测量精度。因此,如何提高关节臂式坐标测量机的测量精度成为研究的焦点与热点。
本论文提出一种可重构的关节臂式坐标测量机,采用变测量空间和变自由度的方法提高测量精度,具体实现方法为采用重构的方式实现关节臂式坐标测量机测量臂长度和关节数目可变,测量时根据被测量工件的几何特点,选择满足工件测量个性化需求的、较少冗余测量空间的方案,提高测量分辨率和测量精度。全文围绕这个思路展开理论分析、系统设计、仿真研究与实验验证工作,主要章节内容包括：
第一章首先介绍关节臂式坐标测量机的研究背景与意义,然后综述国内外关于关节臂式坐标测量机的研究现状、相关产品的优点与不足,最后结合课题任务要求提出本论文的主要研究内容,并对论文的整体构架进行阐述。
第二章介绍可重构的关节臂式坐标测量机的工作原理,将可重构的关节臂式坐标测量机与普通的关节臂式坐标测量机进行对比,阐述可重构的关节臂式坐标测量机在测量精度方面的优势,最后给出可重构的关节臂式坐标测量机的数学计算模型和误差模型。
第三章阐述可重构的关节臂式坐标测量机的设计思路,然后详细介绍可重构的关节臂式坐标测量机机械结构及工作方式。
第四章设计一种基于现场可编程门阵列(FPGA)的数据采集系统,用于可重构的关节臂式坐标测量机的测量系统数据采集,其采集功能包括6路光栅传感器、1路温度传感器以及3个按钮等相关信号的采集和处理,并通过RS-232C串口与计算机通讯。
第五章对可重构的关节臂式坐标测量机的测量空间与测量精度之间的关系进行了研究,主要是对不同臂长、不同自由度配置时测量机的测量误差进行仿真分析和实验验证。基于可重构的关节臂式坐标测量机解析误差模型,采用Matlab软件进行误差仿真分析,并在一台商品化的关节臂式坐标测量机上进行实验验证。
第六章对论文的研究内容和取得的结论进行总结,并对今后的研究工作进行展望。
The articulated arm coordinate measuring machine (AACMM) is a new type of non-cartesian measuring system. Compared with traditional orthogonal coordinate measuring machine it has many advantages such as simple structure, compact size, light weight, large measuring volume, high flexibility, low cost and easy to be used in industrial field. Recently AACMMs have been widely applied in mould design, reverse engineering, quality inspection online, equipment assembly and maintenance and so on. However, the accuracy of AACMMs is much lower than traditional orthogonal coordinate measuring machines, because they are serial mechanisms with many joints and freedoms, the parameter errors transmitting to measuring probe will be accumulated and amplified, on the other hand, the measuring volume of AACMMs is usually much bigger than size of measured parts, therefore it will cause the accuracy loss. So how to improve the accuracy of AACMMs become the focus and hotspot of the research work on AACMMs.
In this thesis, a reconfigurable articulated arm coordinate measuring machine is presented, through an operation of changing measuring volume or decreasing degrees of freedom (DOF) of machine, the new type of machine can meet the requirements of high accuracy as well as high resolution by making the measuring volume fitting to the sizes of measured objects. Around this train of thought, the thesis carries out the theoretical analysis, simulation study and experimental validation.
In the first chapter, the background and the significance of articulated arm coordinate measuring machines are introduced, and then the disadvantages of AACMMs in the market are analyzed. Finally the main framework of the dissertation is presented.
In the second chapter, the work principle of the reconfigurable articulated arm coordinate measuring machine is explained, the advantages of the reconfigurable articulated arm coordinate measuring machine are discussed, then the mathematical model and the error model of the reconfigurable articulated arm coordinate measuring machine are established.
In the third chapter, the mechanical structure of the reconfigurable articulated arm coordinate measuring machine are presented in detailed.
In the fourth chapter, a data acquisition system based on Field Programable Gate Array (FPGA) is designed, which can collect signals of 6 channel circular grating angle sensors,1 channel temperature value, and 3 operation buttons input and communicate with PC based on protocol of RS-232C.
In the fifth chapter, the error simulation and experimental research are carried out. Based on the error model of the reconfigurable articulated arm coordinate measuring machine, the error simulation is carried out with the software of Matlab; finally a validation experiment is carried out with a commercial AACMM product.
In the sixth chapter, the research work is summarized and the futural work is proposed.
引文
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