Scan matching using line segment relationships for map-based localization of mobile robot

A new scan matching method for mobile robot localization is presented, which takes line segment as the feature and matches the real scans in the given reference map by relationships of the directional-defined line segments. The alignment was done by hierarchically identifying the multiple relationships and the result was recorded in a correspondence matrix, where the best match is defined and selected for localization. It is indicated that the searching algorithm of the best match can find the ambiguities and get rid of them. This method with less computational cost works well in occluded environment, and can correct the error in pose estimation without the need for the estimation itself. The efficiency, accuracy and robustness of this method were verified by experiments of localization in an occluded environment and a long-distance indoor navigation.

MC-LRF based pose measurement system for shipborne aircraft automatic landing

Due to the portability and anti-interference ability,vision-based shipborne aircraft automatic landing systems have attracted the attention of researchers.In this paper,a Monocular Camera and Laser Range Finder(MC-LRF)-based pose measurement system is designed for shipborne aircraft automatic landing.First,the system represents the target ship using a set of sparse landmarks,and a two-stage model is adopted to detect landmarks on the target ship.The rough 6D pose is measured by solving a Perspective-n-Point problem.Then,once the rough pose is measured,a region-based pose refinement is used to continuously track the 6D pose in the subsequent image sequences.To address the low accuracy of monocular pose measurement in the depth direction,the designed system adopts a laser range finder to obtain an accurate range value.The measured rough pose is iteratively optimized using the accurate range measurement.Experimental results on synthetic and real images show that the system achieves robust and precise pose measurement of the target ship during automatic landing.The measurement means error is within 0.4in rotation,and 0.2%in translation,meeting the requirements for automatic fixed-wing aircraft landing.

Three-dimensional imaging lidar system based on high speed pseudorandom modulation and photon counting

High speed pseudorandom modulation and photon counting techniques are applied to a three-dimensional imaging lidar system.The specific structure and working principle of the lidar system is described.The actual detector efficiency of a single-photon detector in an imaging system is discussed,and the result shows that a variety of reasons lead to the decrease in detection efficiency.A series of ranging and imaging experiments are conducted,and a series of high-resolution three-dimensional images and a distance value of 1200 m of noncooperative targets are acquired.

Experimental and simulation assessments of underwater light propagation

This paper investigates the light propagation through several types of water by experimental and simulation.The Zemax-ray tracing software allowed to simulate the propagation of light in water and to observe the receiver response by reproducing the real conditions of propagation.The underwater environment has been reproduced by a 1.2 m long water tube and 20 cm in diameter with a glass window fitted on one side.The use of tap water with different amounts of sand leads toward three types of water with different attenuation coefficients(0.133,0.343,0.580 m^-1).The light transmission in the three types of water was experimentally evaluated using a doubled Nd:YAG laser with energy of 4.3 mJ and a pulse width of 20 ns.Comparisons were done between simulation and experimental results.