- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Automatic Mapping of Center Line of Railway Tracks using Global Navigation Satellite System, Inertial Measurement Unit and Laser Scanner
摘要： Up-to-date geodatasets on railway infrastructure are valuable resources for the field of transportation. This paper investigates three methods for mapping the center lines of railway tracks using heterogeneous sensor data: (i) conditional selection of satellite navigation (GNSS) data, (ii) a combination of inertial measurements (IMU data) and GNSS data in a Kalman filtering and smoothing framework and (iii) extraction of center lines from laser scanner data. Several combinations of the methods are compared with a focus on mapping in tree-covered areas. The center lines of the railway tracks are extracted by applying these methods to a test dataset collected by a road-rail vehicle. The guard rails in the test area were also extracted during the center line detection process. The combination of methods (i) and (ii) gave the best result for the track on which the measurement vehicle had moved, mapping almost 100% of the track. The combination of methods (ii) and (iii) and the combination of all three methods gave the best result for the other parallel tracks, mapping between 25% and 80%. The mean perpendicular distance of the mapped center lines from the reference data was 1.49 meters.
关键词： Inertial Measurement Unit,Global Navigation Satellite System,automated mapping,Kalman filter,laser scanner,railway tracks
更新于2025-11-21 11:01:37
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Geometric Calibration of Markerless Optical Surgical Navigation System
摘要： Background: Patient-to-image registration is required for image-guided surgical navigation, but marker-based registration is time consuming and subject to manual error. Markerless registration is an alternative solution to avoid these issues. Methods: This study designs a calibration board and proposes a geometric calibration method to calibrate the near infrared tracking and structured light components of the proposed optical surgical navigation system simultaneously. Results: A planar board and a cylinder are used to evaluate the accuracy of calibration. The mean error for the board experiment is 0.035 mm, and the diameter error for the cylinder experiment is 0.119 mm. A calibration board is reconstructed to evaluate the accuracy of the calibration, and the measured mean error is 0.012 mm. A head phantom is reconstructed and tracked by the proposed optical surgical navigation system. The tracking error is less than 0.3 mm. Conclusions: Experimental results show that the proposed method obtains high accessibility and accuracy and satisfies application requirements.
关键词： Calibration,Markerless,Structure light,Optical surgical navigation system
更新于2025-09-23 15:23:52
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Chip-Scale Molecular Clock
摘要： An ultra-stable time-keeping device is presented, which locks its output clock frequency to the rotational-mode transition of polar gaseous molecules. Based on a high-precision spectrometer in the sub-terahertz (THz) range, our new clocking scheme realizes not only fully electronic operation but also implementations using mainstream CMOS technology. Meanwhile, the small wavelength of probing wave and high absorption intensity of our adopted molecules (carbonyl sulfide, 16O12C32S) also enable miniaturization of the gas cell. All these result in an 'atomic-clock-grade' frequency reference with small size, power, and cost. This paper provides the architectural and chip-design details of the first proof-of-concept molecular clock using a 65-nm CMOS bulk technology. Using a 231.061-GHz phase-locked loop (PLL) with frequency-shift keying (FSK) modulation and a sub-THz FET detector with integrated lock-in function, the chip probes the accurate transition frequency of carbonyl sulfide (OCS) gas inside a single-mode waveguide, and accordingly adjusts the 80-MHz output of a crystal oscillator. The clock consumes only 66 mW of dc power and has a measured Allan deviation of 3.8 × 10^{-10} at an averaging time of τ = 1000 s.
关键词： CMOS,molecular clock,rotational spectroscopy,Allan deviation,GPS,carbonyl sulfide (OCS),frequency stability,navigation
更新于2025-09-23 15:23:52
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[ACM Press the 24th ACM Symposium - Tokyo, Japan (2018.11.28-2018.12.01)] Proceedings of the 24th ACM Symposium on Virtual Reality Software and Technology - VRST '18 - Gaze navigation in the real world by changing visual appearance of objects using projector-camera system
摘要： This paper proposes a method for gaze navigation in the real world by projecting an image onto a real object and changing its appearance. In the proposed method, a camera captures an image of objects in the real world. Next all the pixels in the image but those in a specified region are slightly shifted to left and right. Then the obtained image is projected onto the original objects. As a result, the objects not in the specified region looks blurred. We conducted user experiments and showed that the users’ gaze were navigated to the specified region.
关键词： augmented reality,procam,shift filter,gaze navigation
更新于2025-09-23 15:23:52
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Incoherent Range Walk Compensation for Spaceborne GNSS-R Imaging
摘要： Global navigation satellite system reflectometry (GNSS-R) receivers produce delay-Doppler maps (DDMs) by incoherently integrating coherent integration results. Due to system dynamics, during incoherent integration, the receiver aligns each coherent result by tracking the delay and Doppler of the specular point. This is known to cause a blurring of the spatial footprint of the Woodward ambiguity function (WAF) on the reflecting surface. In this paper, we demonstrate that the blurring of the WAF varies over the glistening zone (GZ), and even if a fixed point on the ground is tracked, blurring still occurs. We derive the expressions for the delay and Doppler change rates over the GZ and then predict the error introduced by range walk for typical GNSS-R scatterometry configurations. We find that ≈6 dB of loss is expected for a point scatterer near the edge of the GZ when a fixed point on the surface is tracked. The incoherent range walk compensation (IRWC) method is then presented for GNSS-R receivers to mitigate this loss. The IRWC method focuses the power in the DDM to the isodelay and iso-Doppler configuration occurring at the midpoint of the integration time. DDMs produced by tracking a fixed point with and without IRWC are simulated, and errors are found to be in agreement with those predicted. Spatial domain GNSS-R products will be improved with IRWC. Target detection will benefit from a larger usable swath, allowing longer tracking and detection times as a result of the increased target to clutter and noise ratio. At the same time, imaging applications will no longer suffer from a spatially variant blurring of the WAF, which limits the resolution of the estimated products. IRWC is shown to mitigate the range migration losses and improve the SNR of an imaging GNSS-R receiver by ≈6 dB near the edge of the GZ.
关键词： integration,global navigation satellite system reflectometry (GNSS-R),reflectometry,imaging,target detection,receiver,incoherent range walk compensation (IRWC),Dynamic corrections
更新于2025-09-23 15:23:52
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Geometric Distortion Correction of Spaceborne GNSS-R Delay-Doppler Map Using Reconstruction
摘要： For spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R), the delay difference of direct and reflected GNSS signals among successive snapshots changes rapidly because of the high dynamics of low earth orbital and GNSS satellites. This change has to be compensated to avoid the distortion of incoherently averaged delay-Doppler map (DDM). The method to refresh the correlation window on each coherent integration time period may require too many instrument resources or too much data to be uploaded from the ground station. This letter proposes a new postprocessing approach based on the motion degradation model of DDM and the reconstruction to replace real-time compensation. Raw sampled data from UK TechDemoSat-1 are used to verify the availability of proposed approach. The results show that after reconstruction for the distorted DDM, the DDM accuracies relative to that compensated in real time are significantly improved.
关键词： Global Navigation Satellite System-Reflectometry (GNSS-R),reconstruction,Distorted delay-Doppler map (DDM)
更新于2025-09-23 15:22:29
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Geometry error analysis in solar Doppler difference navigation for the capture phase
摘要： Deep space exploration missions continue to become more ambitious, driving the need to investigate autonomous navigation systems that are accurate and timely. The solar Doppler difference navigation is a newly-developed and promising celestial autonomous navigation method for use, particularly in the crucial capture period. In this paper, we present novel analyses for three error sources for the solar Doppler difference navigation from the perspective of geometry, motivated with a Mars Deep Space Exploration example. The geometry error sources include the area overlap rate of the direct and the reflected solar light sources, the spread effects related to the time difference of arrival (TDOA) of light, and the solar rotation Doppler difference error. The area overlap rate and the spread effects of TDOA can be utilized to assess the overlap degree of the direct source and the reflected source in both space and time. Theoretical analyses and simulation results demonstrate that the direct and the reflected light sources can be accurately approximated as the same source. The solar rotation Doppler difference error is explored using a velocity error model. This model forms a hemi-ellipsoid that can be utilized to compensate the Doppler error caused by the solar rotation. The three errors decline with the deep space explorer approaching Mars, which means that the performance of the solar Doppler difference navigation method continuously improves in the critical capture period. These results can offer a reference for the system design of the solar Doppler difference navigation.
关键词： error analysis,solar spectrum,Doppler effects,navigation,geometry error
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Intelligent Navigation and Control of a Prototype Autonomous Underwater Vehicle for Automated Inspection of Aquaculture net pen cages
摘要： Aquaculture is one of the fastest growing food sectors worldwide providing more than 50% of world fish consumption. Towards sustainable development, aquaculture ought to design and implement technical solutions for the efficient management of farms, thus improving fish performance and decreasing operational costs, human effort and environmental impact. For this, periodic inspection of fish-cages along with early warning systems are required, functionalities that small-sized underwater vehicles can provide. In this paper, an efficient methodology for intelligent navigation of an Autonomous Underwater Vehicle (AUV) architecture is presented, yielding to a useful tool with advanced capabilities in terms of automated manipulation via real-time optical recognition approaches, miniaturization of sensors and processing units, selective monitoring, data recording/transmission operations and proper parameter calculations for further offline-analysis of captured information. The proposed AUV system constitutes an increased Technology Readiness Level version of the preliminary prototype designed earlier by our group, incorporating additional modules and application capabilities, focusing on regular periodic fish-cage net inspection in terms of net holes and fouling. The optical navigation scheme has been tested in laboratory installations under numerous scenarios so as to determine the factors affecting its robustness and efficiency. Results extracted under the validation procedure in operational conditions indicate that the proposed framework can prove a cost-effective, flexible and operative solution for aquaculture industry, enabling the transfer of operations further offshore.
关键词： remote operation,automated navigation,optical recognition,machine vision,net inspection,autonomous underwater vehicles
更新于2025-09-23 15:22:29
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[IEEE 2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace) - Rome, Italy (2018.6.20-2018.6.22)] 2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace) - Characterization and Testing of a High-Resolution Time-of-Flight Camera for Autonomous Navigation
摘要： This paper presents the results of research activities carried out to characterize and test the operation of a latest generation commercial, high-resolution Time-of-Flight (TOF) camera. The aim is to preliminary evaluate the achievable performance as well as potential limitations related to the use of this instrument for autonomous navigation purposes. Two fields of investigation have been identified: autonomous navigation of Unmanned Aerial Vehicles flying in GPS-denied environments; autonomous relative navigation between non-cooperative space objects. With reference to these applications, first, a metrological characterization has been operated within a laboratory setup. Second, experimental tests have been carried out by processing point clouds acquired by the TOF sensor with state-of-the-art algorithms (for depth-based odometry and non-cooperative pose determination, respectively).
关键词： depth-based odometry,non-cooperative pose determination,TOF camera,autonomous navigation,metrological characterization
更新于2025-09-23 15:22:29
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Context-Aware Depth and Pose Estimation for Bronchoscopic Navigation
摘要： Endobronchial intervention is increasingly used as a minimally invasive means of lung intervention. Vision-based localization approaches are often sensitive to image artifacts in bronchoscopic videos. In this paper, a robust navigation system based on a context-aware depth recovery approach for monocular video images is presented. To handle the artifacts, a conditional generative adversarial learning framework is proposed for reliable depth recovery. The accuracy of depth estimation and camera localization is validated on an in vivo dataset. Both quantitative and qualitative results demonstrate that the depth recovered with the proposed method preserves better structural information of airway lumens in the presence of image artifacts, and the improved camera localization accuracy demonstrates its clinical potential for bronchoscopic navigation.
关键词： Computer Vision for Medical Robotics,Deep Learning in Robotics and Automation,Visual-Based Navigation,Visual Learning
更新于2025-09-23 15:22:29