【作者】 叶晶；

【导师】 平雪良；

【作者基本信息】 江南大学 ， 机械制造及其自动化， 2011， 硕士

【摘要】 螺杆压缩机广泛应用于工业制冷、空气动力等行业,其主要是由一对相互啮合的螺杆转子构成,转子端截面型线的形式直接决定着螺杆压缩机的工作性能。在螺杆压缩机转子的研究方面,我国自主研究开发的转子型线与世界先进水平的转子型线还有相当大的差距,所以如何快速消化、吸收国外先进的螺杆转子型线就是本文研究的主要研究目的,而螺杆转子的逆向工程技术为此提供了新的手段。本文主要在螺杆转子的检测技术、NURBS拟合方法、模型重构等问题上来研究和探讨了螺杆转子型线。采用三坐标测量机(CMM)对螺杆转子进行了初步测量,在研究了转子型线CMM测量的补偿误差后,提出了基于曲面偏置测量法,以实现螺杆转子曲面的快速检测,提高检测效率。论文在理论上验证了该方法的可行性,通过在已知转子CAD原型的螺杆被测曲面及其测量所得偏距面的同一端面上分别截取一条型线进行比较输出误差。研究了螺杆转子型线的数据预处理技术,针对螺杆转子型线测量数据的拟合,本文提出了基于移动最小二乘法的NURBS拟合螺杆型线逆向设计方法。详细介绍了移动最小二乘法(MLS)应用于NURBS曲线拟合的原理及特点,以螺杆转子端面点云数据为实例在MATLAB中实现了移动最小二乘NURBS曲线拟合,与采用传统最小二乘方法得到的拟合曲线相比,提高了精度及光滑性。通过模型重构技术的研究,实现了螺杆转子的模型重构。本文提出的螺杆型线逆向设计方法以及螺杆曲面模型重建的算法,已在Matlab中进实现,并通过实例验证了算法的有效性,为螺杆压缩机生产企业等提供了技术支持与参考信息。更多还原

【Abstract】 Twin-screw compressor are widely applied in industrial refrigeration and air-conditioning. Screw rotors are the key parts of twin-screw compressor. The compressor performance is mainly determined by the screw rotor profile. This thesis concentrates on the researches of the twin-screw rotor measurement technology, fitting the measured rotor profile data and model reconstruction.The thesis presents the mathematical model of screw rotor and proposes a measurement method for screw rotor. While measuring the rotor with Coordinate Measuring Machine (CMM), we obtain two-dimensional coordinate data of central point of the measuring ball. After fitting them to a curve, we generate a screw surface with the curve according to the screw spiral, and then offset the surface by the radius of the ball to attain another screw surface which is the measured surface after error compensation. In order to verify the feasibility of this method, the author extracts a curve in a cross-section from the compensated surface and compares it to the curve extracted from the same cross-section from the known CAD prototype of the screw rotor. In the end, theoretical error of the compensation is analyzed by Imageware which is a professional reverse engineering software.To fit screw rotor profile measured data, the author researches fitting method based on Non-uniform Rational B-spline(NURBS). In order to solve the problem that the connections of fitting curves are not smooth enough, we further proposes a method of reverse design of screw profile based on the moving least square(MLS) of the curve fitting. This method greatly improves smoothness of the fitting curve. With the point data of the measured rotor profile as an instance, the method is realized with the MATLAB and compared with the Traditional Least- Square method.The research achieves the measurement and expression of the advanced twin-screw compressor rotor profile, which will be useful in the rotor development, and provides effective measurement technology.更多还原