Autonomous Landing of Small Unmanned Aerial Rotorcraft Based on Monocular Vision in GPS-denied Area

Focusing on the low-precision attitude of a current small unmanned aerial rotorcraft at the landing stage, the present paper proposes a new attitude control method for the GPS-denied scenario based on the monocular vision. Primarily, a robust landmark detection technique is developed which leverages the well-documented merits of supporting vector machines (SVMs) to enable landmark detection. Then an algorithm of nonlinear optimization based on Newton iteration method for the attitude and position of camera is put forward to reduce the projection error and get an optimized solution. By introducing the wavelet analysis into the adaptive Kalman filter, the high frequency noise of vision is filtered out successfully. At last, automatic landing tests are performed to verify the method's feasibility and effectiveness. © 2014 Chinese Association of Automation.

Segmentation multi-dimensional crest factor reduction for multi-service supporting digital radio over fibre system

A segmentation multi-dimensional crest factor reduction （SMD-CFR） algorithm is proposed for multi-service supporting digital radio over fibre （DRoF） system. Benefit from segmentation dynamic clipping threshold and clipping factor got basing on characteristics of all service bands, the SMD-CFR is able to get better peak clipping and peak to average power ratio （PAPR） reduction for multi-band combined signal. Simulation results show that SMD-CFR gets more than 2.3 reduction in PAPR for two-bands combined signal of long term evolution （LTE） , which is much better than traditional one dimensional （1D）-CFR. Meanwhile, for 64-quadrature amplitude modulation （QAM） modulation and demodulation link, it has very small effect on bit error rate （BER） and error vector magnitude （EVM） , which are controlled less than 0. 1% and 0.2% respectively. For hardware experiment, SMD-CFR obtains 4.5% increase in drain efficiency and about 4 dBc increase in adjacent channel leakage ratio （ACLR）. These are very significant for the wide band power amplifier （PA） in multi-service supporting DRoF system.

Detection of automatic abnormity in the winding and splicing of fiber-optic coil

A high-precision automatic state monitoring and abnormity alarm technique is proposed to solve the process improvement issues of fiber-optic coil winding and splicing. Industrial cameras are used to capture optical and hot images during the assembly of optical components of a fiber-optic gyroscope. A line and contour analysis technique is used to detect abnormal winding. By analyzing the intensity distribution of transmitted light, the graph cut model and multivariate Gaussian mixture model are used to detect and segment the splicing defects. The practical applications indicate the correctness and accuracy of our vision-based technique.