scholarly journals Vision-aided localization and navigation based on trifocal tensor geometry

2017 ◽  
Vol 9 (4) ◽  
pp. 306-317
Author(s):  
Qiang Fang ◽  
DaiBing Zhang ◽  
TianJiang Hu
Keyword(s):  
Three Dimensional ◽  
Inertial Navigation ◽  
Measurement Model ◽  
Geometric Constraints ◽  
Measurement Information ◽  
Trifocal Tensor ◽  
Current Time ◽  
Navigation Algorithm ◽  
Global Positioning ◽  
Primary Contribution

In this paper, a new method for vision-aided navigation based on trifocal tensor geometry is presented. The main goal of the proposed method is to estimate the position of vehicles in global positioning system-denied environments, using a standard inertial navigation system and only a single camera. The geometric trifocal tensor relationship between three images is used as measurement information from the camera, and the primary contribution of this work is the derivation of a measurement model that is able to express the geometric constraints of the trifocal tensor in the global frame. This measurement model does not require including the three-dimensional feature positions in the state vector. In other words, the proposed method does not entail reconstructing the environment. Rather, the method only considers the vehicle state. The vision-aided inertial navigation algorithm that we propose has computational complexity only with regard to the number of features at the current time, and the algorithm is capable of estimating the pose in real environments. Experiments were conducted to show the effectiveness of the proposed method in simulations and real environments.

A method for autonomous collision-free navigation of a quadrotor UAV in unknown tunnel-like environments

Robotica ◽  
2021 ◽  
pp. 1-27
Author(s):  
Taha Elmokadem ◽  
Andrey V. Savkin
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Autonomous Underwater Vehicles ◽  
Three Dimensional ◽  
Underwater Vehicles ◽  
Practical Implementation ◽  
Challenging Problem ◽  
Quadrotor Uav ◽  
Navigation Algorithm ◽  
Aerial Vehicles ◽  
Quadrotor Uavs

Abstract Unmanned aerial vehicles (UAVs) have become essential tools for exploring, mapping and inspection of unknown three-dimensional (3D) tunnel-like environments which is a very challenging problem. A computationally light navigation algorithm is developed in this paper for quadrotor UAVs to autonomously guide the vehicle through such environments. It uses sensors observations to safely guide the UAV along the tunnel axis while avoiding collisions with its walls. The approach is evaluated using several computer simulations with realistic sensing models and practical implementation with a quadrotor UAV. The proposed method is also applicable to other UAV types and autonomous underwater vehicles.

scholarly journals Adaptive Chaotic Image Encryption Algorithm Based on RNA and Pixel Depth

Electronics ◽  
2021 ◽  
Vol 10 (15) ◽  
pp. 1770
Author(s):  
Xiaoqiang Zhang ◽  
Xuangang Yan
Keyword(s):  
Image Encryption ◽  
Three Dimensional ◽  
Encryption Algorithm ◽  
Current Time ◽  
Plain Image ◽  
Scope Of Application ◽  
Selective Diffusion ◽  
Chaotic Image Encryption ◽  
And Diffusion ◽  
Image Encryption Algorithm

To prevent the leakage of image content, image encryption technology has received increasing attention. Most current algorithms are only suitable for the images of certain types and cannot update keys in a timely manner. To tackle such problems, we propose an adaptive chaotic image encryption algorithm based on RNA and pixel depth. Firstly, a novel chaotic system, two-dimensional improved Logistic-adjusted-Sine map is designed. Then, we propose a three-dimensional adaptive Arnold transform for scrambling. Secondly, keys are generated by the hash values of the plain image and current time to achieve one-image, one-key, and one-time pad simultaneously. Thirdly, we build a pre-permuted RNA cube for 3D adaptive scrambling by pixel depth, chaotic sequences, and adaptive RNA coding. Finally, selective diffusion combined with pixel depth and RNA operations is performed, in which the RNA operators are determined by the chemical structure and properties of amino acids. Pixel depth is integrated into the whole procedure of parameter generation, scrambling, and diffusion. Experiments and algorithm analyses show that our algorithm has strong security, desirable performance, and a broader scope of application.

scholarly journals A Dynamic Calibration Method of Installation Misalignment Angles between Two Inertial Navigation Systems

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2947
Author(s):  
Ming Hua ◽  
Kui Li ◽  
Yanhong Lv ◽  
Qi Wu
Keyword(s):  
Autonomous Navigation ◽  
Inertial Navigation ◽  
Calibration Method ◽  
Measurement Information ◽  
Dynamic Calibration ◽  
Navigation Systems ◽  
Inertial Navigation Systems ◽  
Additional Information ◽  
Two Systems ◽  
Dynamic Calibration Method

Generally, in order to ensure the reliability of Navigation system, vehicles are usually equipped with two or more sets of inertial navigation systems (INSs). Fusion of navigation measurement information from different sets of INSs can improve the accuracy of autonomous navigation effectively. However, due to the existence of misalignment angles, the coordinate axes of different systems are usually not in coincidence with each other absolutely, which would lead to serious problems when integrating the attitudes information. Therefore, it is necessary to precisely calibrate and compensate the misalignment angles between different systems. In this paper, a dynamic calibration method of misalignment angles between two systems was proposed. This method uses the speed and attitude information of two sets of INSs during the movement of the vehicle as measurements to dynamically calibrate the misalignment angles of two systems without additional information sources or other external measuring equipment, such as turntable. A mathematical model of misalignment angles between two INSs was established. The simulation experiment and the INSs vehicle experiments were conducted to verify the effectiveness of the method. The results show that the calibration accuracy of misalignment angles between the two sets of systems can reach to 1″ while using the proposed method.

The cathodic reduction of PbO in the passive layer on lead in aqueous sulphuric acid

1984 ◽  
Vol 62 (3) ◽  
pp. 596-600 ◽  
Author(s):  
R. G. Barradas ◽  
D. S. Nadezhdin
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Reference Electrode ◽  
Linear Sweep Voltammetry ◽  
Passive Layer ◽  
Cathodic Reduction ◽  
Linear Sweep ◽  
Current Time ◽  
Lead Monoxide ◽  
Two Peaks

The cathodic reduction of the lead monoxide layer formed on lead in 30% aqueous H2SO4 under anodic oxidation at 0.6 V (vs. Hg/HgSO4 reference electrode) was investigated by linear sweep voltammetry, potential step and admittance measurements. The experimental data were analyzed respectively in terms of thin-layer electrochemistry, electrocrystallisation, and changes of resistance of the PbO layer under reduction. The results seem to be best interpreted from the theory of three-dimensional electrocrystallisation as PbO is reduced to Pb. At sub-zero temperatures the PbO peak observed on our voltammograms and potentiostatic current time transients reveals the splitting of the curves into two peaks, which may be a result of reduction of the same material but of different phases, namely, orthorhombic and tetragonal PbO.

scholarly journals An INS/Geomagnetic Integrated Navigation Algorithm Based on Matching Strategy and Hierarchical Filtering

Electronics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 460
Author(s):  
Xiusheng Duan ◽  
Jing Xiao ◽  
Xiaohui Qi ◽  
Yifei Liu
Keyword(s):  
Magnetic Measurements ◽  
Inertial Navigation ◽  
State Equation ◽  
Integrated Navigation ◽  
Matching Algorithm ◽  
Filtering Algorithm ◽  
Navigation Algorithm ◽  
Physical Experiments ◽  
Matching Strategy ◽  
Navigation Information

To improve the positioning accuracy of an inertial/geomagnetic integrated navigation algorithm, a combined navigation method based on matching strategy and hierarchical filtering is proposed. First, the PDA-ICCP geomagnetic matching algorithm is improved. On basis of evaluating the distribution of magnetic measurements, a number of controllable magnetic values are regenerated to participate in the geomagnetic matching algorithm (GMA). As a result, accuracy of the matching algorithm is ensured and its efficiency is improved. Secondly, the integrated navigation filter is designed based on the hierarchical filtering strategy, in which the navigation information of the geomagnetic matching module and inertial navigation module are respectively filtered and fused in the main filter. In this way, the shortcoming that GMA is unable to provide continuous and real-time navigation information is overcome. Meanwhile, precision of the inertial/geomagnetic integrated navigation algorithm is improved. Finally, the feasibility and validity of the proposed algorithm are verified by simulation and physical experiments. Compared with the integrated filtering algorithm which directly uses the error equation of inertial navigation system (INS) as the state equation, the proposed hierarchical filtering algorithm can achieve higher positioning precision.

scholarly journals On The Parameters of Geometric Constraints for Cracked Plates under Tension – Three-Dimensional Problems

2017 ◽  
Vol 22 (4) ◽  
pp. 901-919 ◽  
Author(s):  
M. Graba
Keyword(s):  
Fracture Toughness ◽  
Comparative Analysis ◽  
Crack Front ◽  
External Load ◽  
Three Dimensional ◽  
Geometric Constraints ◽  
Numerical Calculations ◽  
Cracked Plates ◽  
The Relationship ◽  
Actual Fracture

Abstract This paper provides a comparative analysis of selected parameters of the geometric constraints for cracked plates subjected to tension. The results of three-dimensional numerical calculations were used to assess the distribution of these parameters around the crack front and their changes along the crack front. The study also involved considering the influence of the external load on the averaged values of the parameters of the geometric constraints as well as the relationship between the material constants and the level of the geometric constraints contributing to the actual fracture toughness for certain geometries.

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