Can a Robot Hear the Shape and Dimensions of a Room?

© 2019 IEEE. Knowing the geometry of a space is desirable for many applications, e.g. sound source localization, sound field reproduction or auralization. In circumstances where only acoustic signals can be obtained, estimating the geometry of a room is a challenging proposition. Existing methods have been proposed to reconstruct a room from the room impulse responses (RIRs). However, the sound source and microphones must be deployed in a feasible region of the room for it to work, which is impractical when the room is unknown. This work propose to employ a robot equipped with a sound source and four acoustic sensors, to follow a proposed path planning strategy to moves around the room to collect first image sources for room geometry estimation. The strategy can effectively drives the robot from a random initial location through the room so that the room geometry is guaranteed to be revealed. Effectiveness of the proposed approach is extensively validated in a synthetic environment, where the results obtained are highly promising

Late-time phenomenology required to solve the H0H_0 tension in view of the cosmic ladders and the anisotropic and angular BAO data sets

The $\sim 5\sigma$ mismatch between the value of the Hubble parameter measured by SH0ES and the one inferred from the inverse distance ladder (IDL) constitutes the biggest tension afflicting the standard model of cosmology, which could be pointing to the need of physics beyond $\Lambda$CDM. In this paper we study the background history required to solve the $H_0$ tension if we consider standard prerecombination physics, paying special attention to the role played by the data on baryon acoustic oscillations (BAO) employed to build the IDL. We show that the anisotropic BAO data favor an ultra-late-time (phantom-like) enhancement of $H(z)$ at $z\lesssim 0.2$ to solve the tension, accompanied by a transition in the absolute magnitude of supernovae of Type Ia $M(z)$ in the same redshift range. The effective dark energy (DE) density must be smaller than in the standard model at higher redshifts. Instead, when angular BAO data (claimed to be less subject to model dependencies) is employed in the analysis, we find that the increase of $H(z)$ starts at much higher redshifts, typically in the range $z\sim 0.6-0.9$. In this case, $M(z)$ could experience also a transition (although much smoother) and the effective DE density becomes negative at $z\gtrsim 2$. Both scenarios require a violation of the weak energy condition (WEC), but leave an imprint on completely different redshift ranges and might also have a different impact on the perturbed observables. They allow for the effective crossing of the phantom divide. Finally, we employ two alternative methods to show that current data from cosmic chronometers do not exclude the violation of the WEC, but do not add any strong evidence in its favor neither. Our work puts the accent on the utmost importance of the choice of the BAO data set in the study of the possible solutions to the $H_0$ tension.Comment: 20 pages, 13 figures, 3 table

New Results on Triangulation, Polynomial Equation Solving and Their Application in Global Localization

This thesis addresses the problem of global localization from images. The overall goal is to find the location and the direction of a camera given an image taken with the camera relative a 3D world model. In order to solve the problem several subproblems have to be handled. The two main steps for constructing a system for global localization consist of model building and localization. For the model construction phase we give a new method for triangulation that guarantees that the globally optimal position is attained under the assumption of Gaussian noise in the image measurements. A common framework for the triangulation of points, lines and conics is presented. The second contribution of the thesis is in the field of solving systems of polynomial equations. Many problems in geometrical computer vision lead to computing the real roots of a system of polynomial equations, and several such geometry problems appear in the localization problem. The method presented in the thesis gives a significant improvement in the numerics when Gröbner basis methods are applied. Such methods are often plagued by numerical problems, but by using the fact that the complete Gröbner basis is not needed, the numerics can be improved. In the final part of the thesis we present several new minimal, geometric problems that have not been solved previously. These minimal cases make use of both two and three dimensional correspondences at the same time. The solutions to these minimal problems form the basis of a localization system which aims at improving robustness compared to the state of the art

Machine vision: a survey

This paper surveys the field of machine vision from a computer science perspective. It is written to act as an introduction to the field and presents the reader with references to specific implementations. Machine vision is a complex and developing field that can be broken into the three stages: stereo correspondence, scene reconstruction, and object recognition. We present the techniques and general approaches to each of these stages and summarize the future direction of research

Towards ultrasound full-waveform inversion in medical imaging

Ultrasound imaging is a front-line clinical modality with a wide range of applications. However, there are limitations to conventional methods for some medical imaging problems, including the imaging of the intact brain. The goal of this thesis is to explore and build on recent technological advances in ultrasonics and related areas such as geophysics, including the ultrasound data parallel acquisition hardware, advanced computational techniques for field modelling and for inverse problem solving. With the significant increase in the computational power now available, a particular focus will be put on exploring the potential of full-waveform inversion (FWI), a high-resolution image reconstruction technique which has shown significant success in seismic exploration, for medical imaging applications. In this thesis a range of technologies and systems have been developed in order to improve ultrasound imaging by taking advantage of these recent advances. In the first part of this thesis the application of dual frequency ultrasound for contrast enhanced imaging of neurovasculature in the mouse brain is investigated. Here we demonstrated a significant improvement in the contrast-to-tissue ratio that could be achieved by using a multi-probe, dual frequency imaging system when compared to a conventional approach using a single high frequency probe. However, without a sufficiently accurate calibration method to determine the positioning of these probes the image resolution was found to be significantly reduced. To mitigate the impact of these positioning errors, a second study was carried out to develop a sophisticated dual probe ultrasound tomography acquisition system with a robust methodology for the calibration of transducer positions. This led to a greater focus on the development of ultrasound tomography applications in medical imaging using FWI. A 2.5D brain phantom was designed that consisted of a soft tissue brain model surrounded by a hard skull mimicking material to simulate a transcranial imaging problem. This was used to demonstrate for the first time, as far as we are aware, the experimental feasibility of imaging the brain through skull using FWI. Furthermore, to address the lack of broadband sensors available for medical FWI reconstruction applications, a deep learning neural network was proposed for the bandwidth extension of observed narrowband data. A demonstration of this proposed technique was then carried out by improving the FWI image reconstruction of experimentally acquired breast phantom imaging data. Finally, the FWI imaging method was expanded for3D neuroimaging applications and an in silico feasibility of reconstructing the mouse brain with commercial transducers is demonstrated.Open Acces

Ultrasound based navigation and control for orthopaedic robot surgery

Thesis approved in public session to obtain the PhD Degree in Mechanical Engineering. Universidade de Lisboa. Instituto Superior TécnicoA Robótica cirúrgica é uma área em expansão, contribuindo para o aumento da precisão e exatidão dos procedimentos cirúrgicos, além de produzir resultados mais confiáveis e reprodutíveis, minimizando a invasividade, reduzindo as complicações e melhorando a segurança dos pacientes, comparativamente com as técnicas convencionais. A navegação dentro da sala de operações é primordial para o sucesso dos sistemas robóticos. Neste contexto é proposto um novo sistema de navegação, usado na malha de controlo, de um sistema robótico co-manipulado, dedesenvolvido para auxiliar os cirurgiões ortopédicos. Embora possa ter outras aplicações, o sistema foi desenvolvido para realizar um furo na cabeça do fémur, necessário ao implante do fio guia na cirurgia de substituição parcial da anca. Durante a cirurgia, a posição e orientação do osso é obtida através de um processo de registo entre as imagens de US adquiridas em tempo real e o modelo CT do fémur, previamente carregado no pré-operatório. Contrariamente aos sistemas cirúrgicos atuais, não usa nenhum tipo de implante no osso para localizar o fémur, mas sim marcadores passivos colocados na sonda e no robô, e um sistema de medição óptico para medir as suas posições 3D. Os testes experimentais de validação foram realizados num phantom de um fémur humano.Abstract: Surgical Robotics is an expanding area, contributing to the increased precision and accuracy of surgical procedures, besides producing more reliable and reproducible results, minimizing the invasiveness, reducing complications and improving patient safety, compared with conventional techniques. Navigation within the operating room is fundamental to the success of robotic systems. In this context a new navigation system, used in the control loop, to co-manipulate a robotic system developed to assist orthopaedic surgeons, is proposed. Although it may have other applications, the system is designed to perform a hole in the femur head, necessary to implant the initial guide wire used in Hip Resurfacing surgery. During the surgery, the bone position and orientation is obtained through a registration process between a set of US images acquired in real time and the CT femur model, preloaded pre-operatively. Contrary to current surgical systems, it does not use any type of implant in the bone, to localize the femur, but passive markers, of an optical measurement system, placed on the probe and the robot to measure their 3D poses. Experimental validation tests were performed on a human’s femur phantom, validating the proposed system