Six Degree-of-Freedom Body-Fixed Hovering over Unmapped Asteroids via LIDAR Altimetry and Reinforcement Meta-Learning

We optimize a six degrees of freedom hovering policy using reinforcement meta-learning. The policy maps flash LIDAR measurements directly to on/off spacecraft body-frame thrust commands, allowing hovering at a fixed position and attitude in the asteroid body-fixed reference frame. Importantly, the policy does not require position and velocity estimates, and can operate in environments with unknown dynamics, and without an asteroid shape model or navigation aids. Indeed, during optimization the agent is confronted with a new randomly generated asteroid for each episode, insuring that it does not learn an asteroid's shape, texture, or environmental dynamics. This allows the deployed policy to generalize well to novel asteroid characteristics, which we demonstrate in our experiments. Moreover, our experiments show that the optimized policy adapts to actuator failure and sensor noise. Although the policy is optimized using randomly generated synthetic asteroids, it is tested on two shape models from actual asteroids: Bennu and Itokawa. We find that the policy generalizes well to these shape models. The hovering controller has the potential to simplify mission planning by allowing asteroid body-fixed hovering immediately upon the spacecraft's arrival to an asteroid. This in turn simplifies shape model generation and allows resource mapping via remote sensing immediately upon arrival at the target asteroid.Comment: Earlier version presented at 2020 AIAA Scitech conference. arXiv admin note: substantial text overlap with arXiv:1907.06098, arXiv:1906.0211

Space Objects Classification and Characterization via Deep Learning and Light Curves: Applications to Space Traffic Management

Recent advancements in deep learning (e.g. Convolutional Neural Networks (CNN), Recurrent Neural networks (RNN)) have demonstrated impressive results in many practical and theoretical fields (e.g. speech recognition, computer vision, robotics). Whereas deep learning methods are becoming ubiquitous, they have been barely explored in SSA applications, in particular with regard to object characterization for Space Traffic Management (STM). In this paper, we report the results obtained in designing and training a set of CNNs and RNNs for Space Object (SO) classification and characterization using light-curve measurements. More specifically, we provide a comparison between deep networks trained on both physically-based models (i.e. reflectance models) and real light-curve data (data-driven approach). Physically-based models allow the generation of synthetic light-curves as function of the SO parameters (e.g. shape, size, material). Such models have the ability to yield a large number of training points which make them suitable to train deep networks. Nevertheless, they suffer from modeling errors. Conversely, real light-curve measurements can be employed to directly train CNNs and/or RNNs, yet with a relatively limited data set. Insight in how to design such networks and expected performances will be discussed to highlight the power of the proposed methodology. Additionally, a cluster analysis conducted via data dimensionality reductions coupled with unsupervised feature extractions for SO characterization will be presented

A Koopman-Operator Control Optimization for Relative Motion in Space

A high order optimal control strategy implemented in the Koopman operator framework is proposed in this work. The new technique exploits the Koopman representation of the solution of the equations of motion to develop an energy optimal inverse control methodology. The operator theory can reformulate a nonlinear dynamical system of finite dimension into a linear system with an infinite number of dimensions. As a results, the state of any nonlinear dynamics is represented as a linear combination of high-order orthogonal polynomials, which creates the state transition polynomial map of the solution. Since the optimal control technique can be reduced to a two-points boundary value problem, the Koopman map is used to connect the state and control variables in time, such that optimal values are obtained through map inversion and polynomial evaluation. The new technique is applied to rendezvous applications in space, where the relative motion between two satellites is modelled with a high-order polynomial series expansion of the Lagrangian of the system, such that the Clohessy-Wiltshire equations represent the reduction of the high-order model to a linear truncation.Comment: 19 pages, 9 figures, 2023 SciTech conference. arXiv admin note: text overlap with arXiv:2111.0748

Planejamento integrado das operações de venda e manufatura S&OP: o caso Portobello

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.A existência de planos comerciais e operacionais sinérgicos contribuem para a obtenção de bons resultados financeiros às empresas dos setores produtivos e comerciais. A influência destes planos na cadeia logística também são significativos, pois têm forte participação nas decisões do que comprar, produzir, armazenar, e vender. A sinergia destes planos pode ser alcançada através de um processo contínuo de revisão e monitoramento dos planos comerciais e operacionais, chamado S&OP - Sales and Operations Planning. O S&OP contribui de forma eficaz ao gerenciamento da cadeia logística, pois permite a elaboração de planos de vendas realistas, equilibrados com a capacidade de manufatura interna e externa, sendo fundamental para o dimensionamento correto dos estoques de matérias-primas e produtos acabados. A aplicação do processo de S&OP na portobello, objetivo do presente trabalho, foi desenvolvido a partir da observação da cultura da Portobello, do seu processo de gestão, estratégia e análise de sua cadeia de suprimentos, permitindo a interpretação dos fenômenos que serviram para construir o modelo apresentado. O processo se desenvolve com a apresentação formal do modelo e seus objetivos à diretoria e gerência da empresa. Todos os trabalhos são realizados através de equipes pré-selecionadas e treinadas, responsáveis pelo desenvolvimento dos relatórios gerenciais que permitem a discussão e aprovação dos planos comerciais e operacionais (produção e suprimentos), através da visualização objetiva das previsões de vendas, produção e estoque e de sua eficácia quando comparada a períodos passados. Como resultado temos o equilíbrio dos planos através da visualização antecipada de restrições industriais e comerciais, redução dos estoques de matérias-primas e do nível de serviço ao cliente, expresso em pedido atendido na data prometida

Effects of inertia and turbulence on rheological measurements of neutrally buoyant suspensions

For low-Reynolds-number shear flows of neutrally buoyant suspensions, the shear stress is often modelled using an effective viscosity that depends only on the solid fraction. As the Reynolds number (Re) is increased and inertia becomes important, the effective viscosity also depends on the Reynolds number itself. The current experiments measure the torque for flows of neutrally buoyant particles in a coaxial-cylinder rheometer for solid fractions, ϕ, from 10 % to 50 % and Reynolds numbers based on particle diameter from 2 to 1000. For experiments for Reynolds of O(10) and solid fractions less than 30%, the effective viscosity increases with Reynolds number, in good agreement with recent numerical simulations found in the literature. At higher solid fractions over the same range of Re, the results show a decrease in torque with shear rate. For Reynolds numbers greater than 100 and lower solids concentrations, the effective viscosity continues to increase with Reynolds number. However, based on comparisons with pure fluid measurements the increase in the measured effective viscosity results from the transition to turbulence. The particles augment the turbulence by increasing the magnitude of the measured torques and causing the flow to transition at lower Reynolds numbers. For the highest solid fractions, the measurements show a significant increase in the magnitude of the torques, but the effective viscosity is independent of Reynolds number

Nuevas políticas tributarias e informalidad en el nuevo régimen único simplificado de Cajamarca (2017 - 2019)

El estudio llevado a cabo sobre las nuevas políticas tributarias e informalidad en el Nuevo Régimen Único Simplificado (NRUS), el que tuvo como origen conocer si los lineamientos tributarios llevados a cabo en el periodo 2017-2019, incidieron o no en el mencionado régimen tributario, toda vez que existe cuestionamientos en el sentido que la política tributaria en el país, constituye uno de los factores por los cuales las personas naturales generadoras de renta de tercera categoría acogidas a dicho régimen tributario, se vuelven informales debido a la alta presión tributaria. Asimismo, la investigación hace uso de factores muy importantes, como el empleo de conceptualizaciones, definiciones y otros, en cuanto al marco teórico y el trabajo de campo, con respecto a la parte metodológica a efectos de cumplir con el rigor de la investigación, que sirvió para desarrollar todos los aspectos importantes de la tesis, desde el planteamiento del problema hasta la contratación de la hipótesis. Por otro lado, se reunió toda la información que nos proporcionó la Superintendencia Nacional de Aduanas y Administración Tributaria, el cual fue procesado y, posteriormente se llevó a cabo la interpretación de cuantos contribuyentes acogidos al Nuevo Régimen Único Simplificado generadores de renta de tercera categoría existen hasta el 31 de diciembre del 2016 y cuantos contribuyentes con las nuevas políticas tributarias existen al 31 de diciembre del 2019, para luego llevar a cabo la contratación de las hipótesis. Tal como se puede apreciar en el estudio, se determinó que el papel de la política tributaria que en la economía es importante, donde su diseño debe ser consistente de acuerdo con los objetivos macroeconómicos y como el indicador propuesto se convierte en la herramienta para respectiva evaluación. Además, la efectividad de las herramientas fiscales, cuota impositiva y gasto público, deben estar acorde con la formalización que de los contribuyentes del Nuevo RUS