ABSTRACT: This work deals with the problem of the design of an autonomous redundant system for the attitude determination of nanosatellites. The system consists of a circuit board equipped with three microcontrollers, a magnetic field sensor in three axes, and complementary commercial-of-the-shelf (COTS) components and connectors to provide data signal exchange the vehicle on-board computer. The main goal of this system, named SDATF (of the acronym in Portuguese Sistema de Determinação de Atitude com Tolerância a Falhas), is to provide autonomously the vehicle attitude from the information collected from the onboard computer (OBC) and the magnetometer. The adopted attitude determination algorithm is based on the well-known QUEST method, and the goal of this system is to get accurate attitude computations to low-orbit CubeSat satellites using COTS electronic components, and to provide highly reliable data and high availability levels using fault tolerance tools to avoid the harmful consequences of spatial radiation and its faults known as single event upsets (SEU). The article presents the general design of the fault-tolerant systems and experimental tests using bit flip injection methodology.

ABSTRACT Design candidates obtained from optimization techniques may have meaningful information, which provides not only the best solution, but also a relationship between object functions and design variables. In particular, trade-off studies for optimum airfoil shape design involving various objectives and design variables require the effective analysis tool to take into account a complexity between objectives and design variables. In this study, for the multiple-conflicting objectives that need to be simultaneously fulfilled, the real-coded Adaptive Range Multi-Objective Genetic Algorithm code, which represents the global and stochastic multi-objective evolutionary algorithm, was developed for an airfoil shape design. Furthermore, the PARSEC method reflecting geometrical properties of airfoil is adopted to generate airfoil shapes. In addition, the Self-Organizing Maps, based on the neural network, are used to visualize trade-offs of a relationship between the objective function space and the design variable space obtained by evolutionary computation. The Self-Organizing Maps that can be considered as data mining of the engineering design generate clusters of object functions and design variables as an essential role of trade-off studies. The aerodynamic data for all candidate airfoils is obtained through Computational Fluid Dynamics. Lastly, the relationship between the maximum lift coefficient and maximum lift-to-drag ratio as object functions and 12 airfoil design parameters based on the PARSEC method is investigated using the Self-Organizing Maps method.

ABSTRACT This article deals with the problem of Earth’s magnetic field sensors calibration in the context of low-cost nanosatellites’ navigation systems. The attitude of space vehicles can be determined from the state estimation using information from three-axis inertial and non-inertial sensors. This study considers a three-axis solid-state magnetometer. In the vehicle itself, the presence of ferrous materials and electronic devices creates disturbances, distorting the measured field. The sensor precision can be enhanced through calibration methods which calculate the systematic error. The objective here is to study and implement calibration combining a geometric method and the TWOSTEP algorithm. The methodology is based on numerical simulations, with the development of a database of the Earth’s magnetic field along the vehicle orbit, and experimental tests using a nanosatellite mockup, containing an embedded processor Arduino MEGA 2560 platform and the magnetometer HMC5843.

Abstract: This article has discussed the development of a three-axis attitude digital controller for an artificial satellite using a digital signal processor. The main motivation of this study is the attitude control system of the satellite Multi-Mission Platform, developed by the Brazilian National Institute for Space Research for application in different sort of missions. The controller design was based on the theory of the Linear Quadratic Gaussian Regulator, synthesized from the linearized model of the motion of the satellite, i.e., the kinematics and dynamics of attitude. The attitude actuators considered in this study are pairs of cold gas jets powered by a pulse width/pulse frequency modulator. In the first stage of the project development, a system controller for continuous time was studied with the aim of testing the adequacy of the adopted control. The next steps had included an analysis of discretization techniques, the setting time of sampling rate, and the testing of the digital version of the Linear Quadratic Gaussian Regulator controller in the MATLAB/SIMULINK. To fulfill the study, the controller was implemented in a digital signal processor, specifically the Blackfin BF537 from Analog Devices, along with the pulse width/pulse frequency modulator. The validation tests used a scheme of co-simulation, where the model of the satellite was simulated in MATLAB/SIMULINK, while the controller and modulator were processed in the digital signal processor with a tool called Processor-In-the-Loop, which acted as a data communication link between both environments.function and required time to achieve a given mission accuracy are determined, and results are provided as illustration.

Esse trabalho apresenta um estudo sobre ferramenta computacional para auxílio ao projeto de lapidação de gemas. O material escolhido para o estudo é o quartzo hialino. São apresentados aspectos de desenvolvimento histórico do processamento de gemas e também os diagramas de lapidação e seus principais parâmetros. Para a determinação do grau de eficiência de um modelo de lapidação, são propostos dois critérios: a brilhância e o aproveitamento em peso. A ferramenta computacional, a ser utilizada na estimação desses resultados de um determinado projeto, baseia-se nas redes neurais artificiais. A validação da ferramenta proposta utiliza testes sobre dados de 62 diferentes projetos de lapidação.

This paper presents a study on a Computer-aided-design (CAD) tool for lapidary design. The material chosen is rock crystal quartz. Aspects of historical development of gemstone lapidary, faceting diagrams and faceting parameters are presented. Two criteria are proposed to assess the efficiency of a given lapidary design: brilliance and yield. To estimate these two results, the tool developed is based on artificial neural networks. Tests with 62 different lapidary designs were used to validate the proposed CAD tool.

Este artigo introduz um procedimento para o projeto de circuitos eletrônicos analógicos simples que emulam o comportamento dinâmico de sistemas físicos e matemáticos. Tais circuitos podem ser utilizados como uma aproximação experimental para desenvolvimento de atividades experimentais de ensino, sendo facilmente aplicáveis em qualquer laboratório. Como exemplo, as versões eletrônicas dos sistemas caóticos de Duffing e Rössler são projetadas e implementadas, resultando em protótipos simples, baratos, robustos, versáteis e funcionais.

This work introduces a procedure for analogue electronic circuits design that emulate the dynamic behavior of physical and mathematical systems. Such circuits can be applied as a practical approach for didactic experiments, and easily settled at any laboratory. As instance, electronic version of Duffing and Rössler chaotic systems are designed and implemented, resulting in simple, low cost, robust and functional prototypes.