A Real Time Distributed Approach to Collision Avoidance for Industrial Manipulators

Robot interaction with the surrounding environment is an important and newsworthy problem in the context of industrial and service robotics. Collision avoidance gives the robot the ability to avoid contacts with objects around it, but most of the industrial controls implementing collision avoidance checks only the robot Tool Center Point (TCP) over the objects in the cell, without taking into account the shape of the tool, mounted on the robot flange. In this paper a novel approach is proposed, based on an accurate 3D simulation of the robotic cell. A distributed real time computing approach has been chosen to avoid any overloading of the robot controller. The simulator and the client application are implemented in a personal computer, connected via a TCP-IP socket to the robot controller, which hosts and manages the anti-collision policies, based on a proper speed override control. The real time effectiveness of the proposed approach has been confirmed by experimental tests, carried out for a real industrial setup in two different scenarios

Maps of secular resonances in the NEO region

Context. From numerical simulations, it is known that some secular resonances may affect the motion of near-Earth objects (NEOs). However, the specific location of the secular resonance inside the NEO region is not fully known, because the methods previously used to predict their location can not be used for highly eccentric orbits and when the NEOs cross the orbits of the planets. Aims. In this paper, we aim to map the secular resonances with the planets from Venus to Saturn in the NEO region, even for high values of the eccentricity. Methods. We used an averaged semi-analytical model that can deal with orbit crossing singularities for the computation of the secular dynamics of NEOs, from which we can obtain suitable proper elements and proper frequencies. Then, we computed the proper frequencies over a uniform grid in the proper elements space. Secular resonances are thus located by the level curves corresponding to the proper frequencies of the planets. Results. We determined the location of the secular resonances with the planets from Venus to Saturn, showing that they appear well inside the NEO region. By using full numerical N-body simulations we also showed that the location predicted by our method is fairly accurate. Finally, we provided some indications about possible dynamical paths inside the NEO region, due to the presence of secular resonances.Comment: Accepted for publication in A&

Efectos de cantaxantina dietaria sobre el estres por radiacion ultravioleta en el camarón Artemesia longinaris

The aims of this research were to investigate the effects of diets with added synthetic canthaxanthin (10% parafarm) and to evaluate its possible protective role under ultraviolet radiation (UVR) in prawn Artemesia longinaris. Three isoproteic and isolipidic diets (41% protein and 12% lipid) containing 0 (C0), 100 (C100), and 300 (C300) mg of canthaxanthin kg-1 of diet were prepared. Before initiating the radiation experiment, prawns were fed with the different diets for a period of 21 d in order to determine a possible accumulation of carotenoids. Afterwards, animals were exposed to two radiation treatments for 7 d: a) photosynthetically active radiation (PAR, 400-700 nm), and b) total radiation (PAR+UVR, 280-700 nm), under controlled conditions (19 ± 2 °C, salinity = 33, pH = 7). In animals exposed to PAR+UVR treatment, survival varied between 50 and 83.33% with the highest value in animals fed diet C300. At the end of the experiment, significant statistical differences were registered in integument carotenoid concentration. Under UVR stress, the highest decrease in non-polar carotenoid and esterified astaxanthin were recorded in prawns fed diets containing canthaxanthin. Scavenging properties were evaluated by electron resonance spectroscopy (EPR) using the stable 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical. Prawns fed with C300 showed the greatest activity to quench DPPH. Results suggested that dietary canthaxanthin could be acting as an antioxidant against reactive oxygen species and produced high tolerance under UVR stress.Los objetivos de esta investigación fueron investigar los efectos de dietas adicionadas con cataxantina sintética (10% parafarm) y evaluar su posible papel protector bajo la radiación ultravioleta (RUV) en el camarón Artemesia longinaris. Se prepararon tres dietas isoprotéicas e isolipídicas (41% proteína y 12% lípidos) con 0 (C0), 100 (C100) y 300 (C300) mg de cantaxantina kg-1 de dieta. Previo al experimento de radiación, los camarones fueron alimentados con las diferentes dietas durante 21 d para determinar una posible acumulación de carotenoides. Posteriormente, los animales fueron expuestos a dos tratamientos de radiación durante 7 d: a) radiación fotosintéticamente activa (PAR, 400-700 nm), y b) radiación total (PAR+RUV, 280-700 nm), bajo condiciones controladas (19 ± 2 °C, salinidad = 33, pH = 7). En los individuos expuestos al tratamiento PAR+RUV, la supervivencia varió entre 50 y 83,33%, con el valor más alto en animales alimentados con dieta C300. Al final del experimento, se registraron diferencias estadísticas significativas en la concentración de carotenoides en el tegumento. Bajo estrés por RUV se registró la mayor disminución de carotenoides no polares y astaxantina esterificada en camarones alimentados con dietas con cataxantina. La capacidad antioxidante se evaluó mediante espectroscopía de resonancia electrónica (EPR) utilizando el radical estable 2,2-difenil-2-picrilhidrazilo (DPPH). Los camarones alimentados con C300 mostraron la mayor actividad evidenciada por el decaimiento de DPPH. Los resultados sugirieron que la cantaxantina dietaria podría estar actuando como un antioxidante contra las especies reactivas de oxígeno y producir una alta tolerancia bajo estrés por RUV

Typhoon at CommsNet13: Experimental experience on AUV navigation and localization

This paper presents two acoustic-based techniques for Autonomous Underwater Vehicle (AUV) navigation within an underwater network of fixed sensors. The proposed algorithms exploit the positioning measurements provided by an Ultra-Short Base Line (USBL) transducer on-board the vehicle to aid the navigation task. In the considered framework the acoustic measurements are embedded in the communication network scheme, causing time-varying delays in ranging with the fixed nodes. The results presented are obtained with post-processing elaborations of the raw experimental data collected during the CommsNet13 campaign, organized and scientifically led by the NATO Science and Technology Organization Centre for Maritime Research and Experimentation (CMRE). The experiment involved several research institutions and included among its objectives the evaluation of on-board acoustic USBL systems for navigation and localization of AUVs. The ISME groups of the Universities of Florence and Pisa jointly participated to the experiment with one Typhoon class vehicle. This is a 300 m depth rated AUV with acoustic communication capabilities originally developed by the two groups for archaeological search in the framework of the THESAURUS project. The CommsNet13 Typhoon, equipped with an acoustic modem/USBL head, navigated within the fixed nodes acoustic network deployed by CMRE. This allows the comparison between inertial navigation, acoustic self-localization and ground truth represented by GPS signals (when the vehicle was at the surface)

Autosub Long Range 1500: A continuous 2000 km field trial

Long Range Autonomous Underwater Vehicles (LRAUVs) offer the potential to monitor the ocean at higher spatial and temporal resolutions compared to conventional ship-based techniques. The multi-week to multi-month endurance of LRAUVs enables them to operate independently of a support vessel, creating novel opportunities for ocean observation. The National Oceanography Centre’s Autosub Long Range is one of a small number of vehicles designed for a multi-month endurance. The latest iteration, Autosub Long Range 1500 (ALR1500), is a 1500 m depth-rated LRAUV developed for ocean science in coastal and shelf seas or in the epipelagic and meteorologic regions of the ocean. This paper presents the design of the ALR1500 and results from a five week continuous deployment from Plymouth, UK, to the continental shelf break and back again, a distance of approximately 2000km which consumed half of the installed energy. The LRAUV was unaccompanied throughout the mission and operated continuously beyond visual line of sight

Symmetric Constellations of Satellites Moving Around a Central Body of Large Mass

We consider a (1 + N) -body problem in which one particle has mass m≫ 1 and the remaining N have unitary mass. We can assume that the body with larger mass (central body) is at rest at the origin, coinciding with the center of mass of the N bodies with smaller masses (satellites). The interaction force between two particles is defined through a potential of the form U∼1rα,where α∈ [1 , 2) and r is the distance between the particles. Imposing symmetry and topological constraints, we search for periodic orbits of this system by variational methods. Moreover, we use Γ -convergence theory to study the asymptotic behaviour of these orbits, as the mass of the central body increases. It turns out that the Lagrangian action functional Γ -converges to the action functional of a Kepler problem, defined on a suitable set of loops. In some cases, minimizers of the Γ -limit problem can be easily found, and they are useful to understand the motion of the satellites for large values of m. We discuss some examples, where the symmetry is defined by an action of the groups Z4 , Z2× Z2 and the rotation groups of Platonic polyhedra on the set of loops

Packet-Based Dynamic Control of a Furuta Pendulum over Ethernet

The possibility to remotely control a plant through a communication network offers strong advantages in terms of installation, flexibility, and maintenance. These advantages come at the price of specific challenges due to the format of the transmitted data, the network nodes scheduling, and the inherent delays. To address these obstacles, we have recently developed a control methodology that exploits the packetized nature of the transmitted data by relying on a model-based prediction of the control signal to be applied. However, this methodology was limited to static controllers. Dynamic control laws indeed require a more careful synchronization between the plant and its remote model. This paper aims at filling this gap by exploiting the transmission of the measurements history, rather than their instantaneous value only