Improved Fourier Mellin Invariant for Robust Rotation Estimation with Omni-cameras

Spectral methods such as the improved Fourier Mellin Invariant (iFMI) transform have proved faster, more robust and accurate than feature based methods on image registration. However, iFMI is restricted to work only when the camera moves in 2D space and has not been applied on omni-cameras images so far. In this work, we extend the iFMI method and apply a motion model to estimate an omni-camera's pose when it moves in 3D space. This is particularly useful in field robotics applications to get a rapid and comprehensive view of unstructured environments, and to estimate robustly the robot pose. In the experiment section, we compared the extended iFMI method against ORB and AKAZE feature based approaches on three datasets showing different type of environments: office, lawn and urban scenery (MPI-omni dataset). The results show that our method boosts the accuracy of the robot pose estimation two to four times with respect to the feature registration techniques, while offering lower processing times. Furthermore, the iFMI approach presents the best performance against motion blur typically present in mobile robotics.Comment: 5 pages, 4 figures, 1 tabl

Pose Estimation for Omni-directional Cameras using Sinusoid Fitting

We propose a novel pose estimation method for geometric vision of omni-directional cameras. On the basis of the regularity of the pixel movement after camera pose changes, we formulate and prove the sinusoidal relationship between pixels movement and camera motion. We use the improved Fourier-Mellin invariant (iFMI) algorithm to find the motion of pixels, which was shown to be more accurate and robust than the feature-based methods. While iFMI works only on pin-hole model images and estimates 4 parameters (x, y, yaw, scaling), our method works on panoramic images and estimates the full 6 DoF 3D transform, up to an unknown scale factor. For that we fit the motion of the pixels in the panoramic images, as determined by iFMI, to two sinusoidal functions. The offsets, amplitudes and phase-shifts of the two functions then represent the 3D rotation and translation of the camera between the two images. We perform experiments for 3D rotation, which show that our algorithm outperforms the feature-based methods in accuracy and robustness. We leave the more complex 3D translation experiments for future work.Comment: 8 pages, 5 figures, 1 tabl

A Survey on Global LiDAR Localization

Knowledge about the own pose is key for all mobile robot applications. Thus pose estimation is part of the core functionalities of mobile robots. In the last two decades, LiDAR scanners have become a standard sensor for robot localization and mapping. This article surveys recent progress and advances in LiDAR-based global localization. We start with the problem formulation and explore the application scope. We then present the methodology review covering various global localization topics, such as maps, descriptor extraction, and consistency checks. The contents are organized under three themes. The first is the combination of global place retrieval and local pose estimation. Then the second theme is upgrading single-shot measurement to sequential ones for sequential global localization. The third theme is extending single-robot global localization to cross-robot localization on multi-robot systems. We end this survey with a discussion of open challenges and promising directions on global lidar localization

Novel Camera Architectures for Localization and Mapping on Intelligent Mobile Platforms

Self-localization and environment mapping play a very important role in many robotics application such as autonomous driving and mixed reality consumer products. Although the most powerful solutions rely on a multitude of sensors including lidars and camera, the community maintains a high interest in developing cost-effective, purely vision-based localization and mapping approaches. The core problem of standard vision-only solutions is accuracy and robustness, especially in challenging visual conditions. The thesis aims to introduce new solutions to localization and mapping problems on intelligent mobile devices by taking advantages of novel camera architectures. The thesis investigates on using surround-view multi-camera systems, which combine the benefits of omni-directional measurements with a sufficient baseline for producing measurements in metric scale, and event cameras, that perform well under challenging illumination conditions and have high temporal resolutions. The thesis starts by looking into the motion estimation framework with multi-perspective camera systems. The framework could be divided into two sub-parts, a front-end module that initializes motion and estimates absolute pose after bootstrapping, and a back-end module that refines the estimate over a larger-scale sequence. First, the thesis proposes a complete real-time pipeline for visual odometry with non-overlapping, multi-perspective camera systems, and in particular presents a solution to the scale initialization problem, in order to solve the unobservability of metric scale under degenerate cases with such systems. Second, the thesis focuses on the further improvement of front-end relative pose estimation for vehicle-mounted surround-view multi-camera systems. It presents a new, reliable solution able to handle all kinds of relative displacements in the plane despite the possibly non-holonomic characteristics, and furthermore introduces a novel two-view optimization scheme which minimizes a geometrically relevant error without relying on 3D points related optimization variables. Third, the thesis explores the continues-time parametrization for exact modelling of non-holonomic ground vehicle trajectories in the back-end optimization of visual SLAM pipeline. It demonstrates the use of B-splines for an exact imposition of smooth, non-holonomic trajectories inside the 6 DoF bundle adjustment, and show that a significant improvement in robustness and accuracy in degrading visual conditions can be achieved. In order to deal with challenges in scenarios with high dynamics, low texture distinctiveness, or challenging illumination conditions, the thesis focuses on the solution to localization and mapping problem on Autonomous Ground Vehicle(AGV) using event cameras. Inspired by the time-continuous parametrizations of image warping functions introduced by previous works, the thesis proposes two new algorithms to tackle several motion estimation problems by performing contrast maximization approach. It firstly looks at the fronto-parallel motion estimation of an event camera, in stark contrast to the prior art, a globally optimal solution to this motion estimation problem is derived by using a branch-and-bound optimization scheme. Then, the thesis introduces a new solution to handle the localization and mapping problem of single event camera by continuous ray warping and volumetric contrast maximization, which can perform joint optimization over motion and structure for cameras exerting both translational and rotational displacements in an arbitrarily structured environment. The present thesis thus makes important contributions on both front-end and back-end of SLAM pipelines based on novel, promising camera architectures

A Comprehensive Review on Autonomous Navigation

The field of autonomous mobile robots has undergone dramatic advancements over the past decades. Despite achieving important milestones, several challenges are yet to be addressed. Aggregating the achievements of the robotic community as survey papers is vital to keep the track of current state-of-the-art and the challenges that must be tackled in the future. This paper tries to provide a comprehensive review of autonomous mobile robots covering topics such as sensor types, mobile robot platforms, simulation tools, path planning and following, sensor fusion methods, obstacle avoidance, and SLAM. The urge to present a survey paper is twofold. First, autonomous navigation field evolves fast so writing survey papers regularly is crucial to keep the research community well-aware of the current status of this field. Second, deep learning methods have revolutionized many fields including autonomous navigation. Therefore, it is necessary to give an appropriate treatment of the role of deep learning in autonomous navigation as well which is covered in this paper. Future works and research gaps will also be discussed

Visual odometry from omnidirectional camera

V této práci řešíme problém odhadu pohybu robota výhradně z obrázků pořízených ze všesměrové kamery, která je namontována na robotu (vizuální odometrie). V porovnání s hardware běžně používaným pro visuální odometrii, náš robot je specifický tím, že se pohybuje pomocí pásů a obrázky pořizuje pomoví všesměrové kamery s vysokým rozlišením a nízkou frekvencí snímkování (1 to 3 Hz). V naší práci se zaměřujeme na vysokou přesnost odhadů pohybu ve scénách, kde jsou objekty daleko od kamery. Toto je umožněno použitím všesměrové kamery. U tohoto typu kamer je známo že stabilizují odhad pohybu mezi pozicemi kamer, který je špatně podmíněn u kamer s malým zorným polem. Pro odhad pohybu kamery používáme metodu založenou na detekci rohů. K vůli možnosti velké vzájemné rotace kamer mezi snímky jsme nuceni použít metodu párování rohů namísto trackingu.We present a system that estimates the motion of a robot relying solely on images from onboard omnidirectional camera (visual odometry). Compared to other visual odometry hardware, ours is unusual in utilizing high resolution, low frame-rate (1 to 3 Hz) omnidirectional camera mounted on a robot that is propelled using continuous tracks. We focus on high precision estimates in scenes, where objects are far away from the camera. This is achieved by utilizing omnidirectional camera that is able to stabilize the motion estimates between camera frames that are known to be ill-conditioned for narrow field of view cameras. We employ feature based-approach for estimation camera motion. Given our hardware, possibly high ammounts of camera rotation between frames can occur. Thus we use techniques of feature matching rather than feature tracking.Department of Theoretical Computer Science and Mathematical LogicKatedra teoretické informatiky a matematické logikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Development Of A High Performance Mosaicing And Super-Resolution Algorithm

In this dissertation, a high-performance mosaicing and super-resolution algorithm is described. The scale invariant feature transform (SIFT)-based mosaicing algorithm builds an initial mosaic which is iteratively updated by the robust super resolution algorithm to achieve the final high-resolution mosaic. Two different types of datasets are used for testing: high altitude balloon data and unmanned aerial vehicle data. To evaluate our algorithm, five performance metrics are employed: mean square error, peak signal to noise ratio, singular value decomposition, slope of reciprocal singular value curve, and cumulative probability of blur detection. Extensive testing shows that the proposed algorithm is effective in improving the captured aerial data and the performance metrics are accurate in quantifying the evaluation of the algorithm