Contributions to Localization, Mapping and Navigation in Mobile Robotics

This thesis focuses on the problem of enabling mobile robots to autonomously build world models of their environments and to employ them as a reference to self–localization and navigation. For mobile robots to become truly autonomous and useful, they must be able of reliably moving towards the locations required by their tasks. This simple requirement gives raise to countless problems that have populated research in the mobile robotics community for the last two decades. Among these issues, two of the most relevant are: (i) secure autonomous navigation, that is, moving to a target avoiding collisions and (ii) the employment of an adequate world model for robot self-referencing within the environment and also for locating places of interest. The present thesis introduces several contributions to both research fields. Among the contributions of this thesis we find a novel approach to extend SLAM to large-scale scenarios by means of a seamless integration of geometric and topological map building in a probabilistic framework that estimates the hybrid metric-topological (HMT) state space of the robot path. The proposed framework unifies the research areas of topological mapping, reasoning on topological maps and metric SLAM, providing also a natural integration of SLAM and the “robot awakening” problem. Other contributions of this thesis cover a wide variety of topics, such as optimal estimation in particle filters, a new probabilistic observation model for laser scanners based on consensus theory, a novel measure of the uncertainty in grid mapping, an efficient method for range-only SLAM, a grounded method for partitioning large maps into submaps, a multi-hypotheses approach to grid map matching, and a mathematical framework for extending simple obstacle avoidance methods to realistic robots

Benchmarking Particle Filter Algorithms for Efficient Velodyne-Based Vehicle Localization

Keeping a vehicle well-localized within a prebuilt-map is at the core of any autonomous vehicle navigation system. In this work, we show that both standard SIR sampling and rejection-based optimal sampling are suitable for efficient (10 to 20 ms) real-time pose tracking without feature detection that is using raw point clouds from a 3D LiDAR. Motivated by the large amount of information captured by these sensors, we perform a systematic statistical analysis of how many points are actually required to reach an optimal ratio between efficiency and positioning accuracy. Furthermore, initialization from adverse conditions, e.g., poor GPS signal in urban canyons, we also identify the optimal particle filter settings required to ensure convergence. Our findings include that a decimation factor between 100 and 200 on incoming point clouds provides a large savings in computational cost with a negligible loss in localization accuracy for a VLP-16 scanner. Furthermore, an initial density of ∼2 particles/m 2 is required to achieve 100% convergence success for large-scale (∼100,000 m 2 ), outdoor global localization without any additional hint from GPS or magnetic field sensors. All implementations have been released as open-source software

A Low-Cost Modular Platform for Heterogeneous Data Acquisition with Accurate Interchannel Synchronization

Most experimental fields of science and engineering require the use of data acquisition systems (DAQ), devices in charge of sampling and converting electrical signals into digital data and, typically, performing all of the required signal preconditioning. Since commercial DAQ systems are normally focused on specific types of sensors and actuators, systems engineers may need to employ mutually-incompatible hardware from different manufacturers in applications demanding heterogeneous inputs and outputs, such as small-signal analog inputs, differential quadrature rotatory encoders or variable current outputs. A common undesirable side effect of heterogeneous DAQ hardware is the lack of an accurate synchronization between samples captured by each device. To solve such a problem with low-cost hardware, we present a novel modular DAQ architecture comprising a base board and a set of interchangeable modules. Our main design goal is the ability to sample all sources at predictable, fixed sampling frequencies, with a reduced synchronization mismatch (<1 s) between heterogeneous signal sources. We present experiments in the field of mechanical engineering, illustrating vibration spectrum analyses from piezoelectric accelerometers and, as a novelty in these kinds of experiments, the spectrum of quadrature encoder signals. Part of the design and software will be publicly released online

A 3D Printed Power-Split Device for Testing Energy Management Strategies Applied to Hybrid Vehicles

This work presents a testbed emulating the hybrid electric vehicles powertrain with both teaching and research purposes. The core of this testbed is a 3D printed epicycloidal gearset actuating as a power split device. Its design and hardware equipment are explained as well as its working principle. From an educational point of view, this system states an interesting control problem and, at the same time, exemplifies the operation of this kind of machines with the scope of a motivating application. Consequently, a teaching methodology comprising this testbed is proposed. In addition, the challenging nature of the system encourage the development of optimization techniques aimed at reducing the overall system energy consumption. Results of a preliminary experiment are satisfactory addressed. As a consequence, the presented testbed is proposed as a remote lab for teaching and benchmarking new control strategies

A Factor-Graph-Based Approach to Vehicle Sideslip Angle Estimation

Sideslip angle is an important variable for understanding and monitoring vehicle dynamics, but there is currently no inexpensive method for its direct measurement. Therefore, it is typically estimated from proprioceptive sensors onboard using filtering methods from the family of the Kalman filter. As a novel alternative, this work proposes modeling the problem directly as a graphical model (factor graph), which can then be optimized using a variety of methods, such as whole-dataset batch optimization for offline processing or fixed-lag smoothing for on-line operation. Experimental results on real vehicle datasets validate the proposal, demonstrating a good agreement between estimated and actual sideslip angle, showing similar performance to state-of-the-art methods but with a greater potential for future extensions due to the more flexible mathematical framework. An open-source implementation of the proposed framework has been made available online

Soporte a tres alturas para equipos de medida de parámetros ambientales

Número de publicación: 2 661 542 Número de solicitud: 201600846 51 Int. CI.: F16M 11/42 (2006.01) B25H 1/10 (2006.01)Soporte para equipos de medida de parámetros ambientales, del tipo de los que permiten la colocación de equipos de medida en tres alturas y ajustar dichas posiciones en altura. El soporte incorpora un mástil (1) vertical y tres barras-soporte (2) colocadas en posición horizontal y a distintas alturas. Dichas barras-soporte (2) pueden desplazarse verticalmente por medio de sus respectivos mecanismos piñón-cremallera (3). El mecanismo piñón-cremallera (3) incorpora un gatillo (8) para evitar el desplazamiento de la barra-soporte (2) debido a su propio peso. La barra-soporte (2) presenta en toda su longitud una multitud de agujeros (9) destinados a la ubicación de instrumentos de medida.UNIVERSIDAD DE ALMERÍ

Medio de carga para máquinas de musculación

ES2617959 A1 (20.06.2017) ES2617959 B2 (03.11.2017) P201700130 (30.01.2017)Medio de carga del tipo de los utilizados en máquinas de musculación. El medio de carga incorpora dos guías curvas (1a, 1b) colocadas de forma simétrica y cuyas caras exteriores definen sendas pistas de rodadura (11a, 11b) sobre las que pueden desplazarse sendos rodillos (3a, 3b). Los ejes (4a, 4b) de dichos rodillos (3a, 3b) están unidos entre sí mediante un resorte de extensión (5). Dos tirantes (6a, 6b) unen los ejes (4a, 4b) de sendos rodillos (3a, 3b) con un cable de carga (8). La geometría de la curva definida por las pistas de rodadura (11a, 11b) es tal que la fuerza exterior aplicada sobre el cable de carga (8) es la misma independientemente de la posición en la que se encuentren los rodillos (3a, 3b).UNIVERSIDAD DE ALMERÍ

Ultraviolet Index (UVI) inside an Almería-Type Greenhouse (Southeastern Spain)

Greenhouse workers, despite being in a space beneath a plastic cover, may be susceptible to risks associated to ultraviolet (UV) radiation in skin and eyes. The present work focuses on experimentally analysing this risk throughout a complete year. For this purpose, a network of sensors has been designed, comprising 12 UV radiation measuring stations inside the greenhouse and one outside. It is shown that the UVI risk limit established by World Health Organization (WHO) is exceeded for some particular dates and times, thus there exist risk of damage caused by UV radiation for greenhouse workers. The results allow to identify the UV risk periods for the location studied. A diagram called “UVIgram” has been created which offers weather and UV radiation information for a particular location, for each month, and also in general for the whole year. Finally, a series of recommendations and protection measures are given, highlighting the whitening of the plastic cover of the greenhouse and an alarm system which has been designed to alert workers when UV risk exists

Distributed network for measuring climatic parameters in heterogeneous environments: Application in a greenhouse

En los países mediterráneos del sur de Europa, las condiciones climáticas suelen ser favorables para el cultivo de hortalizas de invernadero, pero no siempre para los trabajadores. El objetivo de este estudio fue diseñar una red de estaciones meteorológicas capaces de recoger datos de parámetros ambientales relacionados con el bienestar de los trabajadores de invernaderos en el sureste de España. Los desequilibrios del ambiente térmico fueron estudiados tanto vertical como horizontalmente siguiendo la norma ISO 7726. Los resultados indican que el invernadero debe ser considerado un ambiente heterogéneo, lo que implica que, para una evaluación de las condiciones ambientales relacionadas con el estrés térmico de los trabajadores, las mediciones se deben tomar a tres alturas (tobillo, abdomen y cabeza) en el interior del invernadero