The angle-based intersection measurement system is a high-precision overall measurement network based on the perspective observation in space. However, when the target is moving, the angular intersection failure will cause dynamic error to limit its application in the field of dynamic measurement. Aiming at this problem, Firstly, this paper analyze the sources of dynamic error from the principle, studies the influencing factors of system dynamic error include :the motion state of the measured object, station deployment. Secondly, constructs a mathematical model to predict the dynamic error of the measurement system. Finally, design some simulation experiments to quantify the measurement dynamic error at different measure conditions. The results show that under the measurement conditions of the measurement area is 10m x 10m x 1m, observation angle uncertainty is 2′′, the measured target moves at 0.05m/s, the average dynamic error of the measured area under the 0_4 deployment is the minimum, and value is 0.25mm.
Aiming at the requirement of high precision real-time measurement of attitude angle in modern manufacturing industry, an attitude measurement system based on a Laser Tracker is constructed. A method of attitude measurement based on 2DPSD and monocular vision is proposed, and a target structure for realizing this method is proposed. Firstly, the rolling angle of the target relative to the camera is calculated by monocular vision, and the laser beam vector is obtained by Laser Tracker and 2DPSD. Then, the relative attitude between the Laser Tracker coordinate system and the camera coordinate system is calculated based on SVD. Finally, the transformation relations of unit vector of laser beam in different coordinate systems are established to calculate the attitude of target relative to Laser Tracker. Experiments show that the method can effectively measure the target attitude information, and the maximum error of attitude angle measurement can be less than 2° within the effective angle range of [- 25°, 25°] and distance range of 3m.
The spectral response of long-period fiber gratings can be tailored by the cladding index perturbation (C-LPFGs) induced by written methods. Here, we investigate theoretically the effects of radial dependence and the magnitude of the cladding index modulation on the transmission spectra of C-LPFGs. Simple analytical expressions that describe the dispersion characteristics of the guided core mode and cladding modes are derived from a multilayer cylindrical waveguide. As the radial depth increases, we demonstrate that transition points exist for the resonances of lower cladding modes, i.e., LP06 and LP15 modes, by comparing the mode-coupling phase to the value π/2. In addition, we show that resonant wavelength shifts of all cladding modes follow the same trend. For the LPvj (v≠0) modes with two polarizations, the cross talk weakens the power exchanges between core mode LP01 and LPvj (v≠0) modes. Moreover, the coupling mechanism relating to cladding index modulation is explained by the presence of the interaction between the evanescent field of the core mode and cladding modes. This work is promising in terms of providing sufficient guidelines to understand and explore design and application of LPFGs.
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