Signal conditioning for the Kalman filter: application to satellite attitude estimation with magnetometer and sun sensors

Most satellites use an on-board attitude estimation system, based on available sensors. In the case of low-cost satellites, which are of increasing interest, it is usual to use magnetometers and Sun sensors. A Kalman filter is commonly recommended for the estimation, to simultaneously exploit the information from sensors and from a mathematical model of the satellite motion. It would be also convenient to adhere to a quaternion representation. This article focuses on some problems linked to this context. The state of the system should be represented in observable form. Singularities due to alignment of measured vectors cause estimation problems. Accommodation of the Kalman filter originates convergence difficulties. The article includes a new proposal that solves these problems, not needing changes in the Kalman filter algorithm. In addition, the article includes assessment of different errors, initialization values for the Kalman filter; and considers the influence of the magnetic dipole moment perturbation, showing how to handle it as part of the Kalman filter framework

MEGARA, the R=6000-20000 IFU and MOS of GTC

MEGARA is the new generation IFU and MOS optical spectrograph built for the 10.4m Gran Telescopio CANARIAS (GTC). The project was developed by a consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain). The instrument arrived to GTC on March 28th 2017 and was successfully integrated and commissioned at the telescope from May to August 2017. During the on-sky commissioning we demonstrated that MEGARA is a powerful and robust instrument that provides on-sky intermediate-to-high spectral resolutions R_(FWHM) ~ 6,000, 12,000 and 20,000 at an unprecedented efficiency for these resolving powers in both its IFU and MOS modes. The IFU covers 12.5 x 11.3 arcsec2 while the MOS mode allows observing up to 92 objects in a region of 3.5 x 3.5 arcmin^(2) . In this paper we describe the instrument main subsystems, including the Folded-Cassegrain unit, the fiber link, the spectrograph, the cryostat, the detector and the control subsystems, and its performance numbers obtained during commissioning where the fulfillment of the instrument requirements is demonstrated

Herramienta integral y de bajo coste para el desarrollo de prácticas remotas para las asignaturas de Ciencias e Ingeniería

Los laboratorios remotos, en los que los alumnos interactúan con los dispositivos reales a través de Internet, incrementa el tiempo de uso de dichos dispositivos por parte de los alumnos y el número de pruebas que pueden realizar durante las experiencias. Sin embargo, para implementarlos, los docentes habitualmente tienen que saber utilizar una serie de tecnologías diferentes, que dificultan su puesta en marcha y mantenimiento. Para paliar estos problemas, en este Proyecto de Innovación y Mejora de la Calidad Docente (PIMCD) se ha desarrollado una nueva metodología desde la que se centraliza la puesta en marcha de todo el laboratorio desde una única herramienta (Easy JavaScript Simulations, EJsS), que sirve tanto para gestionar el código mediante el que se interactúa con los dispositivos, el servidor que da acceso remoto a la práctica, y la interfaz gráfica con la que los alumnos interactúan con los dispositivos. Además, es importante resaltar que es una metodología de bajo coste, ya que desde el punto de vista del proceso de conversión de un laboratorio presencial ya existente en uno remoto, solo necesita una Raspberry PI para desplegar todo el software del laboratorio. Además, en este proyecto también se presentan un conjunto de experiencias desarrolladas con las mismas, que ya están siendo utilizadas por los alumnos en diferentes asignaturas de Ingeniería Electrónica de Comunicaciones y un nuevo laboratorio remoto de Robótica que se pondrá en marcha el curso que viene

The control of specific actuators for fast ferry vertical motion damping

The vertical motions of fast ships, which have a negative effect on comfort and safety, can be attenuated using moving actuators. There is the need of a control strategy to move the actuators in the most convenient way, considering several objectives. The paper considers this problem, studying a practical real example. Experiments with a scaled down replica of a fast ferry has been done, first for modeling purposes and second for control studies. Linear control shows serious application problems. Taking this into consideration, a nonlinear control approach is devised, with satisfactory results

EDROOM. Automatic C++ code generator for real time systems modelled with room

The development of real-time control systems is usually part of a design cycle, involving implementation, experimental control system testing, and re-design. For a faster and better complete development, a software engineering approach, based on a modelling language, is recommended. A successful alternative is ROOM: a modelling language with a graphical syntax. In this paper EdROOM is presented: an environment developed to graphically edit ROOM models and to automatically generate, from the models, C++ real-time control code for direct experimental application. The code generated is modular and easy to debug. The paper describes the design of the environment, with the key aspects of the modelling methodology. EdROOM has been used by our research team for several applications, with satisfactory results. One of these applications concerns the control of actuators of a fast ship for vertical motion smoothing: this is described as an example of EdROOM use

Experimental framework for autonomous fast ships's control design

The research on seakeeping control of fast ships requires difficult experiments for modeling and control design. To alleviate the ship motion certain active appendages are added, such moving flaps, T-foil and fins. The motion of appendages must be optimized to counteract each encountered wave. During our first research steps, a scaled down ship, with scaled appendages, has been used in a towing tank facility. The scaled ship is towed at fixed speeds of experimental interest, for instance at the equivalent to 40 knots. The wavemaker in the towing tank is used to generate specified waves. Along the experiments it was noticed that the towing of the replica spoils certain expected phenomena. A more appropriate way of doing experiments to observe all ship motions, is to use an autonomous self-propelled scaled ship. In this paper a new autonomous scaled ship is presented. It contains an on-board control system, so the ship is self-governed. Complex maneuvering can be programmed for certain study interests. Our autonomous ship is linked via radio with an external monitoring system. The ship and the off-shore monitoring system constitute an experimental framework for advanced studies about fast ship control

Control code generator used for control experiments in ship scale model.

After a study of control design to get a good candidate for testing, it comes a step of experimental confirmation. The general objective of the research is to smooth the vertical motions of a fast ferry. A T-foil and transom flaps are added to a scaled-down replica of the fast ferry. These appendages can move under control. So there is a control system installed on the replica, that moves the appendages using motors, and measures the main variables of the ship and actuators motions. This control system is based on an industrial PC with electronic interfaces for motors and sensors. The control algorithm obtained by the design, must be implemented as real-time control software, to be executed on the industrial PC. For a fast and easy translation from design to real-time application, a new software tool has been developed. This tool generates directly C++ code, easy to compile, from a graphical description of the control. With this tool, the experiments have been achieved in short time. During experiments, several non expected circumstances appear, but this was not a problem: the tool allows for an easy improvement of the original design. The paper describes the tool and its use during experiments

Low cost satellite flying formation control

[Resumen] Los satélites de bajo coste son una revolución en el sector espacial, porque permiten asumir riesgos. Un tipo de misiones arriesgadas son las formaciones en vuelo de satélites, que son muy exigentes desde el punto de vista de la algoritmia de control y del coste de propulsión. Estos satélites tienen el hándicap de su limitada capacidad de propulsión, y las prestaciones reducidas tanto de los sensores como del hardware. Para asegurar que la misión ofrezca una autonomía suficiente, es necesario estudiar modos de operación que supongan un mínimo coste de propulsión. En este artículo se presenta un análisis matemático del problema y se proponen diferentes modos de operación que minimizan el consumo del sistema de propulsión, analizando también diferentes estrategias de control.[Abstract] Low-cost satellites are a revolution in the space sector, because they allow you to take risks. Satellite flying formations are risky missions, they are very demanding from the point of view of the control algorithm and the cost of propulsion. These satellites have the handicap of their limited propulsion capacity, and the reduced performance of both sensors and hardware. To ensure that the mission offers sufficient autonomy, it is necessary to study modes of operation that suppose a minimum cost of propulsion. This article presents a mathematical analysis of the problem and proposes different modes of operation that minimize the consumption of the propulsion system, also analyzing different control strategies

Development of an eIOT Framework Using DEVS: Cyanobacterial Bloom Alert and Management System

[Resumen] Se utiliza Discrete Event System Specification (DEVS) como herramienta para modelar, simular, desarrollar y desplegar un proyecto acorde al paradigma Internet de la Cosas Medioambiental (EIoT). El software/hardware se diseña y desarrolla con una arquitectura típica de IoT, por capas: Cloud, Fog, Edge y Things. Se presenta como caso de aplicación un sistema para monitorizar y controlar Unmaned Surface Vehicles (USVs) que toman medidas en masas de agua dulce con el objetivo de monitorizar y predecir Blooms de cianobacterias. Modelar un proyecto EIoT utilizando DEVS permite un diseño software progresivo, que a su vez facilita mezclar elementos simulados y reales. Este diseño dirigido por modelos permite refinar los modelos mediante simulaciones, para facilitar el despliegue final del sistema real.[Abstract] The Discrete Event System Specification (DEVS) is used to model, simulate, develop and deploy a project according to the Environmental Internet of Things (EIoT) paradigm. The software and hardware are designed and developed following a typical IoT architecture, with layers: Cloud, Fog, Edge and Things. As an application case, a system to monitor and control unmanned surface vehicles (USVs) that perform measurements in freshwater bodies to monitor and predict cyanobacteria blooms is presented. Modeling an EIoT project using DEVS enables a progressive design of the software/hardware, which in turn facilitates the coexistence of simulated and real elements. This model-based design allows the models to be refined through simulations, facilitating the final deployment of the real system.Este trabajo ha sido financiado a través de los proyectos IA-GES-BLOOM-CM (Ref: Y2020/TCS6420) y AMPBAS RETOSINVESTIGACIÓN (Ref: RTI2018-098962-B-C21)https://doi.org/10.17979/spudc.978849749841

Aspectos prácticos del control de actitud del satélite INTA-Nanosat-1B

[Resumen] Los Subsistemas de Determinación y Control de Actitud (ADCS) de las misiones satelitales ambiciosas utilizan habitualmente sensores y actuadores de muy altas prestaciones, como sensores estelares, girómetros laser y ruedas de reacción. En misiones de bajo coste no es posible utilizar estos sensores y actuadores por limitaciones presupuestarias. En estos casos es típico resolver el problema de la determinación con sensores magnéticos y solares, como es el caso del satélite INTA-Nanosat-1B (NS-1B). En muchas situaciones estos sensores no proporcionan suficiente información o precisión para determinar la actitud del satélite, por lo que es necesario subsanar estas deficiencias con una algoritmia más complicada. En NS-1B es necesario propagar matemáticamente la actitud del satélite durante el eclipse. Para ello es necesario caracterizar la principal perturbación que éste sufre, que es el Momento generado por el Dipolo Magnético (MDM). El artículo presenta diferentes aspectos práctico del ADCS de NS-1B, como los diferentes modos de determinación de actitud, la calibración en vuelo del magnetómetro y la estimación también en vuelo del MDM. Se muestra que estas aportaciones mejoran significativamente la precisión del ADCS en la zona de eclipse. Trasladar estas calibraciones y estimaciones a etapas de vuelo supone un ahorro significativo en costes y tiempo que puede ser interesante para misiones de bajo coste, como los CubeSats.Los autores quieren agradecer al Programa de Nanosatélites del INTA por apostar por el desarrollo del conocimiento, en lugar de limitarse a comprar soluciones. También es de agradecer la financiación obtenida por el CICYT a través del proyecto DPI2013-46665-C1https://doi.org/10.17979/spudc.978849749808