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Shadow-Robust Silhouette Reconstruction for Small-Body Applications

JOURNAL OF SPACECRAFT AND ROCKETS 2023年第3期60卷 812-828页

作者： Panicucci, Paolo Lebreton, Jeremy Brochard, Roland Zenou, Emmanuel Delpech, Michel ISAE SUPAERO Complex Syst Engn Dept 10 Ave Edouard Belin F-31400 Toulouse France Ctr Natl Etud Spatiales 18 Ave Edouard Belin F-31400 Toulouse France Airbus Def & Space 31 Rue Cosmonautes F-31400 Toulouse France Politecn Milan Dept Aerosp Sci & Technol Milan Italy Complex Syst Engn Dept 10 Ave Edouard Belin Toulouse France Ctr Natl Etud Spatiales Future Mission Engn Dept 18 Ave Edouard Belin F-31400 Toulouse France

Small bodies' exploration highlighted the need to develop new algorithms for deep space probes navigation. The estimation of the small-body shape is a crucial step for relative navigation, mission planning, and gravity investigation. This paper develops a shape from silhouette algorithm that takes as input a series of images to construct a polyhedral shape for small bodies of the solar system. First, the silhouette associated with the visible part of the body is extracted and modified to account for shadowing effects. Second, the shape is computed by intersecting the viewing cones, i.e., the cone whose apex is the camera center and whose vertices are the silhouette points. The algorithm output is a polyhedral shape whose reconstruction is robust to shadowing. The algorithm is validated by reconstructing the shape of Itokawa and Bennu from synthetic images simulated with Airbus Defence & Space's rendering engine SurRender (TM). Moreover, the algorithm is tested on real images from Hayabusa's approach. Results prove the capability to provide an efficient shape reconstruction for small-body applications.

关键词： Planetary Science and Exploration Space Probe Asteroids computing and informatics Algorithms and Data Structures Vision for Space Exploration Vision Based Navigation Space Exploration and Technology Self-Shadowing Effects Optical Sensor

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Vision-Based Marker-Less Landing of an Unmanned Aerial System on Moving Ground Vehicle

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2024年第9期21卷 735-750页

作者： Krpec, Blake Valasek, John Nogar, Stephen Texas A&M Univ Coll Stn TX 77843 USA Texas A&M Univ Aerosp Engn Dept Vehicle Syst & Control Lab College Stn TX 77843 USA DEVCOM Army Res Lab Aberdeen Proving Ground MD 21005 USA Southwest Res Inst Intelligent Syst Div Robot Auton Sect San Antonio TX 78238 USA

Current autonomous unmanned aerial systems (UASs) commonly use vision-based landing solutions that depend upon fiducial markers to localize a static or mobile landing target relative to the UAS. This paper develops and demonstrates an alternative method to fiducial markers with a combination of neural-network-based object detection and camera intrinsic properties to localize an unmanned ground vehicle (UGV) and enable autonomous landing. Implementing this visual approach is challenging given the limited compute power on board the UAS, but it is relevant for autonomous landings on targets for which affixing a fiducial marker a priori is not possible or not practical. The position estimate of the UGV is used to formulate a landing trajectory that is then input to the flight controller. Algorithms are tailored toward low size, weight, and power constraints, as all compute and sensing components weigh less than 100 g. Landings were successfully demonstrated in both simulation and experimentally on a UGV traveling in both a straight line and while turning. Simulation landings were successful at UGV speeds of up to 3.0 m/s, and experimental landings at speeds up to 1.0 m/s.

关键词： Unmanned Ground Vehicle Image Processing Artificial Neural Network Vision Based Landing Unmanned Aerial Systems Flight Control Surfaces Extended Kalman Filter Autopilot computing and informatics Embedded computing System

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Dynamic Modal Reanalysis Using Flexibility Disassembly Perturbation Method

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AIAA JOURNAL 2024年第9期62卷 3474-3490页

作者： Yang, Qiuwei Peng, Xi Ningbo Univ Technol Engn Res Ctr Ind Construct Civil Engn Zhejiang Sch Civil & Transportat Engn Ningbo 315211 Peoples R China

In structural optimization design and reliability analysis, it is necessary to repeatedly modify the structure and calculate the corresponding vibration modal parameters. It will require significant computational costs if a complete analysis is used to calculate the vibration modes of each modified structure. In order to improve computational efficiency, this work develops a dynamic modal reanalysis method based on flexibility disassembly perturbation, which utilizes the modal data of the original structure to quickly calculate the modal parameters of the modified structure. The core idea of the proposed method is to use the flexibility matrix decomposition formula to quickly calculate the flexibility matrix after each modification of the structure and then obtain a high-precision reduced eigenvalue problem for solving the vibration modes of the modified structure. Three numerical examples are used to validate the proposed modal reanalysis method. It has been shown that the proposed method has higher computational accuracy and efficiency than the existing modal reanalysis method, especially for high-rank and large modification scenarios.

关键词： Mathematical Analysis Finite Element Modeling Structural Design and Development Reduced Order Modelling Statistical Analysis Mechanical Properties computing and informatics Nonlinear Dynamic Analysis Structural System

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The Epoch-State Filter, Revisited

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2023年第7期46卷 1228-1242页

作者： Carpenter, J. Russell NASA Goddard Space Flight Ctr Space Sci Mission Operat Tech Code 444 Greenbelt MD 20771 USA

The epoch-state filter is a recursive sequential estimator that maintains its state estimate and associated covariance at a fixed time known as the epoch, avoiding the need to propagate the covariance between measurements. Instead, the filter maps measurement innovations from the measurement time to the epoch time, in a fashion similar to a batch estimator. When process noise is present, the epoch time must follow all but at most the penultimate measurement. Revisiting the topic, this paper contributes several variations, including a factorized form, a factorized information form, and sigma-point versions, and provides a number of clarifying illustrative examples.

关键词： Kalman Filter Algorithms and Data Structures Mathematical Analysis Celestial Mechanics Satellites computing and informatics Navigation Algorithm

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Numerical Analysis of Initialization of a Nanosecond-Pulsed Dielectric Barrier Discharge Actuator

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AIAA JOURNAL 2024年第10期62卷 3591-3603页

作者： Murzionak, Aliaksandr Mullane, Katrina Etele, J. Carleton Univ Dept Mech & Aerosp Engn Ottawa ON K1S 5B6 Canada

In this work a nanosecond-pulsed dielectric barrier discharge actuator is simulated to investigate the plasma and surface charge behavior during the startup phases of a given pulse sequence. A potential of plus/minus 1.2 kV is applied sinusoidally with a total pulse width of 100 ns over five full pulses. These results show that plasma development changes substantially between the first three pulses, where the distribution of free electrons resulting from the previous pulse influences the development of the plasma sheath and hence the downstream extent of the bulk plasma. Between the third and fifth pulses, a negative surface charge region persists at the downstream extent of the plasma, which generates an electron void, thus inhibiting the development of a strongly ionizing plasma sheath. These results show that by five pulses the plasma has reached its maximum extent and that for the purposes of establishing average values the first two pulses should not be considered representative of the longer-term plasma behavior.

关键词： Actuators Numerical Simulation Dielectric Barrier Discharge Electron Temperature Electric Field Strength Low Pressure Turbine Conservation of Momentum Equations Lumped Element Modeling High Speed Flows computing and informatics

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Leveraging Large Language Models for Tradespace Exploration

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JOURNAL OF SPACECRAFT AND ROCKETS 2024年第5期61卷 1165-1183页

作者： Apaza, Gabriel Selva, Daniel Texas A&M Univ College Stn TX 77843 USA Aerosp Engn Dept 710 Ross St College Stn TX USA

This paper proposes a method for leveraging large language models (LLMs) to improve the question-answering capabilities of artificial intelligence (AI) assistants for tradespace exploration. The method operates by querying an information space composed of fused data sources encompassing the tradespace exploration process and responding based on the gathered information. The information retrieval process is modeled as an internal dialog where an LLM-based dialog agent converses with a subquery answering agent. A case study is conducted on a next-generation soil moisture mission (SM-NG), and a generative AI assistant (named Daphne-G) is configured on it. The effect of the dialog agent and the choice of LLM are assessed by comparing the performance of three different system configurations on a validation question set. A second validation effort is conducted, comparing Daphne-G's responses to those of a baseline template-based AI assistant, Daphne-VA. Results show that the dialog-based system is necessary for answering complex questions requiring multiple documents. Furthermore, results show that Daphne-G can correctly answer all the questions Daphne-VA can answer, while simultaneously being able to answer a greater number of questions than Daphne-VA. The results suggest that LLMs could significantly improve the outcomes of the tradespace exploration process, which may result in better and more cost-effective mission concepts being implemented.

关键词： Natural Language Processing Attitude Determination and Control System Satellite Bus Tropical Rainfall Measuring Mission Renewable Energy Model Based System Engineering Synthetic Aperture Radar Sun Synchronous Orbit Data Products computing and informatics

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Fixed- and Free-Mode Flutter Derivatives During Aeroelastic Optimization

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AIAA JOURNAL 2024年第12期62卷 4645-4653页

作者： Stanford, Bret K. Thelen, Andrew S. Jacobson, Kevin E. NASA Langley Res Ctr Aeroelasticity Branch Res Aerosp Engineer Hampton VA 23681 USA

Aeroelastic flutter design derivatives may be approximated by ignoring the sensitivity of the structural mode shapes. This fixed-mode derivative is less expensive to compute than the exact free-mode derivative (which accommodates the mode shape dependency) but also may provide inaccurate sensitivities for optimization. This work formulates both fixed- and free-mode flutter derivatives and demonstrates the conditions under which they are equivalent. Two different types of fixed-mode derivatives are also developed in this work. Using a cantilevered-plate demonstration problem with both shape and sizing design parameters, the accuracy of the free-mode derivative and the two fixed-mode derivatives is demonstrated via gradient-based optimization.

关键词： High Aspect Ratio Finite Element Analysis Low Aspect Ratio Wings Structural Dynamics and Characterization Aerodynamic Force Aircraft Design Software Computational Fluid Dynamics Subsonic Flow Aircraft Wing Design computing and informatics

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Evaluation of Uncertainties of Pressure Gain Measurements in Rotating Detonation Combustor

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AIAA JOURNAL 2024年第1期62卷 108-126页

作者： Feleo, Alexander D. Gamba, Mirko Univ Michigan Dept Aerosp Engn Ann Arbor MI 48109 USA

Experimentally measuring the pressure gain of a rotating detonation combustor through the method of equivalent available pressure is prone to many experimental uncertainties. A detailed analysis of sources of random and systematic uncertainties in the thrust and pressure gain is performed using data from a hydrogen/air-operated rotating detonation combustor. The combustor had an axial air inlet and a 50% exit constriction. The measured (negative) pressure gain values agree with the results in the literature for similar inlet-to-exit area ratios. The base drag correction on the centerbody was found to be the greatest source of uncertainty for the thrust. While thrust is the predominant source of random uncertainty in the pressure gain calculation, significant systematic errors can be committed due to the assumed exit Mach number. The impact of this assumption becomes more detrimental the closer to positive the measured pressure gain is. By experimentally evaluating the exit Mach number, the random and systematic uncertainty in pressure gain both decreased, indicating that this should be an essential step. A definitive demonstration of gain is challenging, given the assessed uncertainties, and recommendations are provided to increase the precision of the equivalent available pressure methodology.

关键词： Rotating Detonation Combustor Choking Mach Number Equivalent Available Pressure Mass Flow Rate Combustion Efficiency Fluid Mechanics computing and informatics Pressure Transducers Detonation Waves Gas Constant

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Reachability Analysis for Atmospheric Reentry Vehicle

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2024年第1期47卷 133-142页

作者： Patel, Jinaykumar Subbarao, Kamesh Univ Texas Arlington Dept Mech & Aerosp Engn Arlington TX 76019 USA

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Decentralized Observation Allocation for a Large-Scale Constellation

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2023年第8期20卷 447-461页

作者： Parjan, Shreya Chien, Steve A. CALTECH Jet Prop Lab Pasadena CA 91109 USA

Increased space sensing enables new measurements of a wide range of Earth science phenomena including volcanism, flooding, wildfires, and weather. Large-scale observation constellations of hundreds of assets have already been deployed (for example, Planet Labs's Dove satellites), and several constellations of tens of thousands of assets are planned. New challenges exist to rapidly assimilate available data and to optimize measurements by directing spacecraft assets to best observe complex Earth science phenomena. Centralized approaches to managing request allocation in these large constellations are constrained by 1) the need to assign/elect a central node to assign requests to spacecraft and 2) reliance on a single agent communicating with potentially thousands of dependent agents. On the other hand, entirely decentralized approaches to request allocation and observation are prone to oversatisfaction of some requests and undersatisfaction of others due to a lack of communication among agents. In large constellations, an intermediary method is necessary to solve the request allocation problem in a distributed manner. We present distributed artificial intelligence/multiagent methods that leverage existing work on distributed constraint optimization to allocate observations in a satellite constellation. We compare their performance to centralized and highly decentralized approaches using realistic orbits and observation request distributions. Our distributed algorithms can find approximate solutions to the large-scale constellation request allocation problem with low data volume for agent coordination and extend to continuous planning problems with varying request sets and availability of spacecraft agents.

关键词： Distributed Artificial Intelligence Algorithms and Data Structures computing and informatics Optimization Algorithm Satellite Remote Sensing Earth Observation Satellite Multi-Agent System

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