Research Of Wide Range Profile Measurement Method Based On Interference Angle Compensation

Nowadays a growing number of products, such as bearings, gears, I-beam, have ahigher precision requirements in the measurement of the surface morphology precisionin machinery manufacturing industry. The traditional surface topography measuringinstrument can not take into account the requirements of high-precision and large-range.Thus, a cantilevered measurement method with the combination of the probe sensor andactuator control has been proposed. Cantilever beam will produce a deflection of slightangle when it has a displacement movement online, due to the gap between the sliderwhich is used to drive the cantilever beam movement with the rail and the uneven forceof rail, abbe declination error is generated in the measurement process. Therefore, howto achieve the simultaneous measurement of slight angle and displacement measurementbecame the core of the system. For this purpose, this paper presents the measurementaccuracy and error analysis of the system through experimental research and analysisbased on the design of optical system and software and hardware.First, based on the establish of simultaneous optical measurement system of angleand displacement, focusing on the design and analysis of interference angle of theinterferometer system. The relationship of fringes number and Abbe declination whichis been measured has been established under the premise of normal counting conditionsof the fringes width in expected or interference angle. By simulation and experiment,selecting an appropriate width of the fringes to make the influence of the shape to thecount minimal, which is to ensure the accurate displacement measurement. In theanalysis of the role of the beam expander optical system, we get the measuring range ofthe Abbe declination of the system by deducing the relationship between the phasedifference and deflection angle of signal received.Secondly, A new type of photodetector circuit has been designed to receive theinterference fringes. Compared the two photoelectric conversion circuit from thesignal-to-noise ratio and frequency response by establishing the circuit noise model andsystem frequency response functions, that show that this method has a highersignal-to-noise ratio and response speed. Experiment collected and analyzed the staticlight intensity signal and interference fringe in high-speed movement. Moreover, adifferential circuit is designed to eliminate the interference of background light intensitysignal.Thirdly, the system hardware and software design have been completed based onUSB and FPGA. In order to complete the access to the peripherals, a dedicated IP core,such as motor-driven or fringe counting, has been designed in the use of NIOS IIsoft-core as the SOPC system core. We deduced the principle of stepper motor controland discussed how to control the speed to avoid phenomenon of out-of-step orovershoot in motor drive design. Then the communication protocol of the host computerand SOPC has been analyzed. Finally, comparison of the displacement and angle values measured between themeasurement system and the laser interferometer and autocollimator, verifying thereliability of the system. Simultaneously, the error analysis from the experimentalenvironment, schematic, electronic components and hardware circuit has been given.