Self-mixing interferometry (SMI), as an extremely simple and compact laser range finding technique, is especially appropriate to develop minitype sensors for narrow space and small precision parts. In order to enhance the distance resolution performance of this technique, we described the mechanism of nonlinearity in laser frequency under injected current tuning, and proposed a current reshaping method to linearize the laser frequency to attain higher resolution in the scheme of SMI. The proof of nonlinearity was obtained through numerical simulation by considering the change of temperature and carrier concentration and experiment by complex wavelet analysis. The current reshaping method, based on the experimental data of wavelength versus injected current, was proposed to suppress the nonlinearity and improve the distance resolution to better than 20 μm over the range of 2.4-20.4 cm. The influence of tuning parameters and other sources of error was discussed additionally.
Purpose
– This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution.
Design/methodology/approach
– Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat.
Findings
– Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force.
Originality/value
– To the authors
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knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.
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