Wide dynamic guided cannonballs need to be air-aligned after firing, and the precise acquisition of their initial roll angle has been a technical difficulty in the industry. In order to solve the problem that the driveless MEMS gyroscope cannot calculate the initial roll angle on a gentle trajectory, and the attitude information obtained by solving only the crest point is too few, this paper proposes a combined measurement scheme of driveless MEMS gyroscope and accelerometer based on adaptive complementary filtering technology, and the extended Kalman filter and Hilbert transform are used to solve the attitude calculation, which can obtain comprehensive attitude information and solve the problem of gentle trajectory attitude measurement of guided projectile. Both theoretical curve analysis and experimental results analysis prove the effectiveness of the method in this paper.
In order to meet the demand for portable use of the spectrometer and improve the spectral acquisition rate, the driving circuit of the miniature fiber optic spectrometer was designed. The system uses Ibsen Photonic's FSV-101 miniature fiber optic spectrometer, which integrates the S11639-01 high sensitivity Complementary Metal-Oxide Semiconductor (CMOS) image sensor. The main control chip is Field-Programmable Gate Array (FPGA), and the analog-to-digital conversion of the CMOS output signal is performed by A/D conversion chip. The system uses FPGA to drive the CMOS timing and A/D conversion timing, and then communicates with the host computer through the serial port, transmits the spectral data to the host computer for dynamic display of the spectrum. In order to verify the overall performance of the system, laser light sources were used to conduct spectral acquisition experiments. The experimental results show that the system accurately outputs the spectral data of the light source, the spectral acquisition range is 200-1000nm, the frame rate is 111Hz, and the acquisition accuracy is 8bit, which has good practicability.
For the accurate cavity-length demodulation of fiber-optic Fabry–Perot (FP) sensors, a combined correlation method based on the fundamental cross-correlation and a higher-order one is proposed, simulated, and experimentally verified. By extending the reflection spectrum eightfold through continuous frequency-doubling three times, cross-correlation using both the original and eightfold spectra, and determination of the main peak of the fundamental cross-correlation coefficient function with the assistance of the eighth-order cross-correlation coefficient, the cavity-length demodulation resolution for fiber-optic FP sensors can be significantly improved even when the spectral bandwidth of the source is limited or the cavity length is relatively short. A cavity length resolution better than 1.8 nm is achieved for an FP sensor with a cavity length of ∼162 μm. The proposed demodulation method can effectively reduce the bandwidth requirement of the light source for the cavity-length extraction of fiber-optic FP sensors, particularly those with relatively short cavity lengths.
To realize precise absolute distance measurement, an all-fiber beat-frequency laser heterodyne distance measurement system based on a fiber-optic interferometric structure was proposed and demonstrated. An acousto-optic frequency shifter is introduced into one arm of a fiber-optic Mach–Zenhder interferormeter to generate the beat-frequency laser beams in two fiber-optic paths. By a ternary sinusoidal curve fitting method to extract the initial phases of the two beat-frequency laser signals and their phase difference, a distance measurement precision of several tens micrometers can be realized in a distance range of several meters. Experiments showed a maximum relative error of 0.0548% and a resolution of 83.333 μm in a distance range of 0 to 600 mm.
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