| Combined with the New Century Excellent Talents Program in Ministry of Education (project number: NCET-07-0262), "Research on multi-degree of freedom measurement of orthogonal grating and related technology", a measurement system with grating-inductive combination was designed, which relies on optical auto-collimation system for Abbe compensation. It solves the problem of meeting the measuring requirements of large range and high accuracy for surface profile of complex parts at the same time. The related studies on this measurement system are carried on as follows:First, this dissertation analyzes and compares the advantages and shortcomings of several different surface profiler. And combined with the characteristics of this research project, precise diffraction grating and the differential inductance sensor are used as the displacement measuring parts in the design of this assembled profile measuring instrument with large range and high accuracy. And then, its overall structural and measuring principle are described.Secondly, the grating measuring system base on diffraction grating has been designed completed. This dissertation has described the measurement theory of precise diffraction grating and methods of obtaining Moire fringe signals. This dissertation has processed the Moire fringe signals by using resistor chain subsection and hardware four sub-subsection. In resistor chain subsection, the zero-crossing comparator works in the form of direct conduction, so it can simplify the circuit structure. And this dissertation has combined the circuit with programmable logic devices GAL16V8 to handle the grating pattern signal and has completed a five-segment Moire fringe signal processing.Finally, by FPGA hardware, precise sub-processing of the grating signal has been realized, which will greatly improve system accuracy.Thirdly, a high- accuracy method base on auto-collimation and constant optical path to measure deflection error of guide movement angle has been applied to the cantilever lifting mechanism. The experimental results show that this system could provide constant optical path and effectively detect the two dimensional Abbe errors in both directions when the cantilever beam moves up or down, which is driven by leadscrew and linear guideway and realize real-time dynamic measurement. Abbe errors in combination measurement have been effectively compensated and eliminated. As a result, the measurement accuracy of the system is greatly improved.Finally, three kinds of sensors including grating sensor, inductive sensors and angle sensor applied in this experiment have been calibrated and the error has been analyzed. Technical parameters and measuring method of the combined profile measurement system has been verified. By analysis of the experimental data, it is proved that this inductive grating measuring instrument meets the requirements of large range and high- accuracy. |
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