关节臂式坐标测量机反转参数辨识方法研究

Articulated arm coordinate measuring machine is a new type of non-orthogonal system. Its advantages include small volume, lightweight, flexible movement, being convenient to be measured and the cheap price. By studying the key technology of articulated arm coordinate measuring machine in this project, we can set up the math model of articulated arm coordinate measuring machine and research the compensation method of angle encoder error, geometrical error, thermal deformation error, motion error. we also can develop a set of new methods to calibrate parameters of every systems for articulated arm coordinate measuring machine. The calibration method based on reversal method and it got the position of zero and the coordinate axis of the spherical coordinate system model by relative measurements. This method makes the process of the calibration is simple and useful and also made the parameters separation easily achieved. A stable and reliable distributed data acquisition system can be designed, the data acquisition system can process the error compensation according to the math model. It gets three-dimensional coordinate of the measured point and displayed and saves the three-dimensional coordinate in real time. Started form the measuring space and freedom of the articulated arm coordinate measuring machine, then we can built a adjustable articulated arm coordinate measuring machine. It resolves the problem between large measure space, multi-degree of freedom and high resolution, high measurement. So a prototype of independent intellectual property for the articulated arm coordinate measuring machine can be developed. It also has the advantages of high degree of accuracy, easy to the field measurement and cheap price.

关节臂式坐标测量机作为一种新型的多自由度非笛卡尔式坐标测量系统，具有体积小、重量轻、运动灵活、方便现场行测量、价格较便宜等优点。本项目拟通过对关节臂式坐标测量机的关键技术研究，建立关节臂式坐标测量机数学模型，研究角度编码器误差、形位误差、热变形误差、运动误差的补偿方法，提出一整套标定关节臂式坐标测量机各系统参数的新方法。即根据多次反转采用相对测量得到球坐标系统模型中的各关节的零位和坐标轴的位置，使得标定过程简单实用，参数分离容易实现。设计稳定可靠的分布式数据采集系统，此数据采集模式根据建立的数学模型进行误差补偿，并求取被测点的三维坐标、适时显示和保存点的三维坐标。从关节臂式测量机的测量空间和自由度入手，构建现场可调整的关节臂式坐标测量机，解决大测量空间、多自由度与高分辨率、高测量精度之间的矛盾，从而形成有自主知识产权的、精度高且可方便现场进行测量、价格便宜的关节臂式坐标测量机样机方案。

精度是关节臂式坐标测量机的最重要关键技术指标之一，对关节臂式坐标测量机的参数进行标定可以有效地提高它的测量精度。但是目前采用的传统标定方法，具有计算量大、标定过程复杂、标定成本高，需要制作专门的标准器件等不足。针对上述问题，提出一种关节臂式坐标测量机的反转参数标定方法。设计制作了一套对关节臂式坐标测量机的各个关节进行固紧和锁死的机械夹具装置，对关节臂式坐标测量机的臂长、偏置和垂直度误差等参数进行了标定。并利用这些参数对理想运动学模型进行了修正，得到补偿后的模型。利用测量标准球的实验，验证修正后测量的标准球直径的相对误差从0.384%提高到了0.225%。通过实验分析了关节臂式坐标测量机的主要误差源，确定出了影响关节臂式坐标测量机测量误差的主要参数，找出了关节臂式坐标测量机长度误差补偿模型的输入参数。建立关节臂式坐标测量机长度误差补偿模型之前，利用粒子群优化算法（PSO）的BP神经网络模型和多元非线性回归模型对关节臂式坐标测量机进行了空间误差建模，可分别对测量精度提高了31.8%和25%。并针对关节臂式坐标测量机测头和被测对象间测力及其热变形对精度的影响，建立了误差补偿模型，测力对测头直径造成的误差经补偿后，精度可提高87.7%；在20℃实验温度下，热变形误差的补偿，其平均测量误差从71.5um降到33.5um。