Real-time kinematics for accurate geolocalization of images in telerobotic applications

The paper discusses a real-time kinematic system for accurate geolocalization of images, acquired though stereoscopic cameras mounted on a robot, particularly a teleoperated machinery. A teleoperated vehicle may be used to explore an unsafe environment and to acquire in real-time stereoscopic images through two cameras mounted on top of it. Each camera has a visible image sensor. For night operation, or in case temperature is an important parameter, each camera can be equipped with both visible and infrared image sensors. One of the main issues for telerobotic is the real-time and accurate geolocalization of the images, where an accuracy of few cm is required. Such value is much better than that that provided by GPS (Global Positioning System), which is in the order of few meters. To this aim, a real-time kinematic system is proposed which acquires the GPS signal of the vehicle, plus through an RF channel, the GPS signal of a reference base station, geolocalized with a cm-accuracy. To improve the robustness of the differential GPS system, also the data of an Inertial Measurement Unit are used. Another issue addressed in this paper is the real-time implementation of a stereoscopic image-processing algorithm to recover the 3D structure of the scene. The focus is on the 3D reconstruction of the scene to have the reference trajectory for the actuation done by a robotic arm with a proper end-effector

Implicit Cooperative Positioning in Vehicular Networks

Absolute positioning of vehicles is based on Global Navigation Satellite Systems (GNSS) combined with on-board sensors and high-resolution maps. In Cooperative Intelligent Transportation Systems (C-ITS), the positioning performance can be augmented by means of vehicular networks that enable vehicles to share location-related information. This paper presents an Implicit Cooperative Positioning (ICP) algorithm that exploits the Vehicle-to-Vehicle (V2V) connectivity in an innovative manner, avoiding the use of explicit V2V measurements such as ranging. In the ICP approach, vehicles jointly localize non-cooperative physical features (such as people, traffic lights or inactive cars) in the surrounding areas, and use them as common noisy reference points to refine their location estimates. Information on sensed features are fused through V2V links by a consensus procedure, nested within a message passing algorithm, to enhance the vehicle localization accuracy. As positioning does not rely on explicit ranging information between vehicles, the proposed ICP method is amenable to implementation with off-the-shelf vehicular communication hardware. The localization algorithm is validated in different traffic scenarios, including a crossroad area with heterogeneous conditions in terms of feature density and V2V connectivity, as well as a real urban area by using Simulation of Urban MObility (SUMO) for traffic data generation. Performance results show that the proposed ICP method can significantly improve the vehicle location accuracy compared to the stand-alone GNSS, especially in harsh environments, such as in urban canyons, where the GNSS signal is highly degraded or denied.Comment: 15 pages, 10 figures, in review, 201

Static and dynamic performance evaluation of low-cost RTK GPS receivers

The performance of low-cost RTK(real-time kinematic)GPS receivers hasbeen compared to a state-of-the-art system as well to each other. Both static and dynamic performanceshavebeen compared. The dynamic performance has been evaluated using a vehicle with driving robot on the AstaZero proving ground.The assembly of the low-cost RTK GPS receivers is presented, and the test set-ups described. Besides having a lower data output frequency, two of the low-cost receivers have static and dynamic performance not far fromthat of the state-of-the-art system.Research supported by Swedish Transport Administration/Skyltfonden through contract TRV 2015/15562, and Swedish Governmental Agency for Innovation Systems/FFI through contracts 2015-02330 and 2015-03112.Itransi

Guiado GNSS de tractores; análisis de diferentes opciones en el posicionamiento

En este trabajo se evalúa el rendimiento de sistemas de corrección GNSS gratuitos en el guiado de tractores. Se evaluaron tres tipos de receptores GNSS, un Navilock NL-8022MP, un Novatel Smart2 y un Harxon TS108PRO, tres sistemas de corrección, EGNOS, NRTK y RTK, y una tecnología propia, GLIDE, en pruebas en estático. Los resultados de estas pruebas en estático, sugieren que (i) los receptores GPS de bajo coste de 100 € sin datos de corrección permitirían guiar el tractor con errores típicos a corto plazo entre pasadas de alrededor de 1 metro RMS, precisión que permite un guiado regular en fertilización cuando la referencia es una pasada anterior realizada en la última hora; (ii) EGNOS mejora la precisión de guiado permitiendo alcanzar errores a corto plazo entre pasadas de 0.5 metros RMS, precisión que permitiría un guiado bueno en fertilización, y un guiado regular en aplicación de herbicidas; (iii) GNSS+EGNOS+GLIDE mejora el guiado de precisión hasta alcanzar errores entre pasadas a corto plazo de 10 cm, precisión que permitiría un guiado aceptable en fertilización y pulverización, y un guiado regular en siembra, cosecha y labranza; (iv) NRTK alcanza un guiado de precisión a corto y largo plazo de 2 cm, precisión que permitiría un guiado muy preciso en todas las tareas agrícolas con una única restricción: al menos una estación de referencia debe estar a menos de 50 km del tractor; y (v) RTK alcanza una precisión de guiado a corto y largo plazo de 1 cm, precisión que permitiría un guiado muy preciso en todas las tareas agrícolas sin restricciones, pero requiere colocar una costosa estación de referencia cerca del tractor, no estando entonces justificado el uso de RTK si los agricultores disponen de NRTK.This paper evaluates the performance of no fee GNSS augmentation systems in tractor guidance. Three GNSS receivers, a Navilock NL-8022MP, a Novatel Smart2 and a Harxon TS108PRO, three augmentation systems, EGNOS, NRTK and RTK, and a proprietary technology, GLIDE, were evaluated in static tests. The results of these static tests suggest that (i) the low-cost 100 € GPS receivers without augmentation data would allow guide tractor guidance with typical short-term pass-to-pass errors of about 1 meter RMS, an accuracy that allows regular guidance in fertilizing when the reference is a previous pass performed in the last hour; (ii) EGNOS improves the guidance accuracy by allowing to reach short-term pass-to-pass errors of 0.5 meters RMS, accuracy that would allow good guidance in fertilizing, and regular guidance in spraying (iii) GNSS+EGNOS+GLIDE improves precision guidance to reach short-term pass-to-pass errors of 10 cm, an accuracy that would allow fair guidance in fertilizing and spraying, and poor guidance in seeding, harvesting and tilling; (iv) NRTK achieves short-term and long-term precision guidance of 2 cm, an accuracy that would allow very accurate guidance in all agricultural tasks with only one restriction: at least one reference station must be closer than 50 km to the tractor; and (v) RTK achieves a short-term and long-term guidance accuracy of 1 cm, an accuracy that would allow very accurate guidance in all agricultural tasks without restrictions, but requires placing an expensive reference station close to the tractor, not being then justified the use of RTK if no fee NRTK is available to farmers.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaGrado en Ingeniería de Tecnologías Específicas de Telecomunicació

UNMANNED AIRCRAFT SYSTEMS FOR PRECISION METEOROLOGY: AN ANALYSIS OF GNSS POSITION MEASUREMENT ERROR AND EMBEDDED SENSOR DEVELOPMENT

The overarching objective of this research was to enhance our comprehension of the three-dimensional precision of meteorological measurements obtained using small unmanned aircraft systems (UAS). Two complimentary experiments were conducted to achieve this objective. The first experiment entailed the development and implementation of a system to determine the global navigation satellite system (GNSS) position accuracy on a UAS platform. This system was utilized to assess the static and dynamic accuracy of L1 and L1/L2 GNSS receivers in real-time kinematic (RTK) and non-RTK fix modes. Adjusted two-sample t-tests revealed significant differences in horizontal and vertical error between RTK and non-RTK receivers across the various deployment strategies. The findings indicate that RTK receivers produce more precise measurements with significantly fewer errors compared to non-RTK receivers. However, the practical significance of these differences warrants separate consideration. The study emphasizes the importance of using RTK receivers when conducting meteorological measurements, especially vertical profiles, and suggests the need for further research to differentiate the impact of treatments from the influence of external factors on receiver accuracy. The second experiment involved the development of a set of miniature pressure, temperature, and relative humidity (PTH) probes for UAS integration. An automated calibration/validation routine was devised to calibrate the PTH probes using an environmental chamber. The results of the Tukey-Kramer procedures revealed that fewer calibrated sensors were statistically different from each other compared to uncalibrated sensors, reducing intersensory bias and demonstrating the value of calibrating different sensor models to a common reference. The linear regression offsets showed that calibration was necessary to meet the desired accuracy specification. In most UAS-based applications, the differences between the calibrated PTH probes were expected to be negligible, irrespective of their significance. The outcomes of this research will enhance our ability to quantify minor variations in ambient conditions during coordinated multi-UAS flights. The low-cost GNSS receivers evaluated demonstrated centimeter-level accuracy under RTK mode, which eliminates the need to use barometric pressure sensors to correct for short-term drift in elevation from non-RTK GNSS measurements. The PTH probes demonstrated that research-grade meteorological measurements can be made using embedded sensors through careful design and calibration

AI and IoT Meet Mobile Machines: Towards a Smart Working Site

Infrastructure construction is society's cornerstone and economics' catalyst. Therefore, improving mobile machinery's efficiency and reducing their cost of use have enormous economic benefits in the vast and growing construction market. In this thesis, I envision a novel concept smart working site to increase productivity through fleet management from multiple aspects and with Artificial Intelligence (AI) and Internet of Things (IoT)