Key Techniques On The Measurement For Large Diameter Using Multi-roller Method

The precision measurement for the large diameter is continuously a difficult problem in the large dimension measurement for quite some time. It is also a problem to be solved imperatively in the manufacturing of the heavy mechanical and electrical installations and national defense industry, for example, the rotor spindle, large bearing in the manufacture of the water turbogenerator and the giant steamer. In this paper, a multi-roller method is proposed to improve the measurement accuracy of a large shaft diameter aim at the intrinsiclimitations of single-roller method------sliding, pressure-deformation, thermal-deformationand erring in roundness. In the measuring system designed, the sliding signals are eliminated using multi-roller measurement and data fusion technique, and the measurement errors generating by thermal-deformation and pressure-deformation are separated and corrected as well, which improve measurement accuracy remarkably.The main contents of the thesis includes as follows:A multi-rolling-wheel method is proposed based on the analyzing and discussing of the limitations of single-roller method. The principle of measurement and the structure of the system are introduced;The error sources of the multi-roller-based measurement method for large shaft are analyzed completely, and the corresponding correcting methods are proposed, which improves the measurement accuracy of the designed system;The data acquisition and its control system based on virtual instrument in the multi-roller measurement method is designed and developed. The choices of the sensors and the circuits in data acquisition and the construction of the system, as well as the design and realization of the acquisition and its control software are introduced;The roundness error separation method for large shaft in frequency domain is discussed. The studies show that it is difficult to use the 3-probe method in the measurement of roundness errors for large shaft because of the restriction of measurement condition and theexistence of the harmonic suppression. Therefore a new separation method------nonlinearindependent component analysis is proposed to separate the roundness errors and the gyration errors of the workpiece-spindle system in the 3-point measurement method.The roundness errors of a workpiece are measured using 3-point method. The experiment data are processed using the error separation method of NIC A respectively. The experiment results show that the roundness error separation technique based on NICA is simple, practical, and efficient.