An On-Board Visual-Based Attitude Estimation System For Unmanned Aerial Vehicle Mapping

This paper evaluates the performances of several salient feature detectors, namely; Harris detector, Minimum Eigenvalue (MinEig), Scale Invariant Feature Transform (SIFT), Maximally Stable Extremal Region (MSER), Speeded Up Robust Feature (SURF), Features from Accelerated Segment Test (FAST), and Binary Robust Scale Invariant Keypoint (BRISK), in order to assess the suitability in the application of the proposed visual-based attitude estimation system. Throughout the experiment, three main requirements have been investigated which include Time-to-Complete (TTC), detection rate, and matching rate. It was found that SURF fulfills each of the system’s requirements. Moreover, it was also found that keypoints detection capabilities affect the processing time, and the clustering patterns in the results may assist in automated inspection of correct and false matching

The Algorithm for Determining the TOE and Camber Parameters in the 3D vision System

The process of calculating exterior camera parameters is described according to the theory of machine vision. To calculate the toe and camber angles, an algorithm for obtaining the direction vector of wheel axle was developed. Algorithm can be used as well, when the lift plane is not horizontal

Registration Using Projective Reconstruction for Augmented Reality Systems

In AR systems, registration is one of the most difficult problems currently limiting their applications. In this paper, we proposed a simple registration method using projective reconstruction. This method consists of two steps: embedding and tracking. Embedding involves specifying four points to build the world coordinate system on which a virtual object will be superimposed. In tracking, a projective reconstruction technique in computer vision is used to track the four specified points to compute the modelview transformation for augmentation. This method is simple as only four points need to be specified at the embedding stage, and the virtual object can then be easily augmented in a real video sequence. In addition, it can be extended to a common scenario using a common projective matrix. The proposed method has three advantages: (1) It is fast because the linear least square method can be used to estimate the related matrix in the algorithm and it is not necessary to calculate the fundamental matrix in the extended case; (2) A virtual object can still be superimposed on a related area even if some parts of the specified area are occluded during the augmentation process; and (3) This method is robust because it remains effective even when not all the reference points are detected during the augmentation process (in the rendering process), as long as at least six pairs of related reference point correspondences can be found. Several projective matrices obtained from the authors’ previous work, which are unrelated with the present AR system, were tested on this extended registration method. Experiments showed that these projective matrices can also be utilized for tracking the specified points.Singapore-MIT Alliance (SMA

Automatic Calibration of Cameras with Special Motions

We consider the problem of auto-calibrating the intrinsic parameters of a camera moving with a special motion: the rotation axis of the camera being perpendicular to its translation direction. Our method for calibrating the camera is based on Kruppa’s equation which in general requires solving a set of nonlinear equations. We prove in a theorem how to recover the true scale of the Kruppa’s equation from the eigenvalues of a matrix formed using the fundamental matrix between two views

Automating Active Stereo Vision Calibration Process with Cobots

Collaborative robots help the academia and industry to accelerate the work by introducing a new concept of cooperation between human and robot. In this paper, a calibration process for an active stereo vision rig has been automated to accelerate the task and improve the quality of the calibration. As illustrated in this paper by using Baxter Robot, the calibration process has been done faster by three times in comparison to the manual calibration that depends on the human. The quality of the calibration was improved by 120% when the Baxter robot was used

Camera calibration from surfaces of revolution

This paper addresses the problem of calibrating a pinhole camera from images of a surface of revolution. Camera calibration is the process of determining the intrinsic or internal parameters (i.e., aspect ratio, focal length, and principal point) of a camera, and it is important for both motion estimation and metric reconstruction of 3D models. In this paper, a novel and simple calibration technique is introduced, which is based on exploiting the symmetry of images of surfaces of revolution. Traditional techniques for camera calibration involve taking images of some precisely machined calibration pattern (such as a calibration grid). The use of surfaces of revolution, which are commonly found in daily life (e.g., bowls and vases), makes the process easier as a result of the reduced cost and increased accessibility of the calibration objects. In this paper, it is shown that two images of a surface of revolution will provide enough information for determining the aspect ratio, focal length, and principal point of a camera with fixed intrinsic parameters. The algorithms presented in this paper have been implemented and tested with both synthetic and real data. Experimental results show that the camera calibration method presented here is both practical and accurate.published_or_final_versio

Volumetric Monitoring and Modeling of Indoor Air Pollutant Dispersion by the Use of 3D Particle Tracking Velocimetry

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