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High-fidelity simulations of the unsteady flow and radiated noise of a UAV propeller are presented herein. We aim at capturing the broad-band noise associated with both the propeller and its wake. The current results are found to ...
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High-fidelity simulations of the unsteady flow and radiated noise of a UAV propeller are presented herein. We aim at capturing the broad-band noise associated with both the propeller and its wake. The current results are found to be in good agreement with several data including the thrust generated, the unsteady flow structure, as well as the radiated sound spectra and directivity. We focus on understanding the physics of the turbulence-generated noise and how it propagates to the near- and the far- acoustic fields. This is analyzed by computing the dilatation field, the Lighthill-stress terms, and each term in the integrand of FWH integral solution of the far field.
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摘要 :
High-fidelity simulations of the unsteady flow and radiated noise of a UAV propeller are presented herein. We aim at capturing the broad-band noise associated with both the propeller and its wake. The current results are found to ...
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High-fidelity simulations of the unsteady flow and radiated noise of a UAV propeller are presented herein. We aim at capturing the broad-band noise associated with both the propeller and its wake. The current results are found to be in good agreement with several data including the thrust generated, the unsteady flow structure, as well as the radiated sound spectra and directivity. We focus on understanding the physics of the turbulence-generated noise and how it propagates to the near- and the far- acoustic fields. This is analyzed by computing the dilatation field, the Lighthill-stress terms, and each term in the integrand of FWH integral solution of the far field.
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Multi-spacecraft missions involving a fleet of small satellites are gaining significant interest due to low-cost, versatility through reconfiguration, and robustness to failure via redundancy. However, having multiple spacecraft i...
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Multi-spacecraft missions involving a fleet of small satellites are gaining significant interest due to low-cost, versatility through reconfiguration, and robustness to failure via redundancy. However, having multiple spacecraft increases complexity of the system and likelihood of fault occurrence due to large number of components involved. A health management system (HMS) that can effectively detect and identify faults within a complex system is required. In this work, we propose a novel data-driven HMS for multi-spacecraft system that is inspired by artificial immune system (AIS) in biology. The developed HMS utilizes notion of self and non-self to distinguish nominal conditions from off-nominal states due to fault. In the process, antibodies (detectors) are generated from dataset of nominal flight data and support vector machine algorithms is employed for classification in the high-dimensional feature space. The proposed HMS is applied to a design reference mission that involves a fleet of spacecraft performing on-orbit inspection in low Earth orbit. The performance and capabilities of the architecture is validated through numerical simulations where spacecraft in the network are subjected to various faults. The result show promise of AlS-based HMS in effectively detecting and identifying faults for multi-spacecraft systems.
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The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading...
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The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading conditions while also considering the safety and comfort of the astronauts. One of the critical load cases in spacesuit design is a low-velocity impact (LVI) which may occur due to tool drop and other similar scenarios. The objectives of this work were (a) to create a finite element (FE) model of a component of a spacesuit, (b) validation of the FE model through experiments, (c) creating an optimization framework to design the spacesuit component, and (d) investigate the effect of finite difference step size on the final optimized design. A FE model of a plate was created to represent a part of the spacesuit's hard upper torso (HUT), which is made of a sandwich structure with S2 glass fiber composite (outer layers) and carbon fiber composite (core) materials. The FE model was used to simulate the nonlinear LVI response of the plate using MSC Nastran and were validated against the displacement and contact force history obtained from the LVI experiment using the Instron Impact Test instrument. Further, the sandwich plate was optimized for an impact load case with sizing variables (thickness and ply orientation) and shape variables (length and width) using quadratic, sinusoidal and Hicks-Henne bump shape function. The objective was to minimize weight while being subjected to displacement or stress constraints. The effect of the finite difference step size variation on the shape optimization of the plate was studied. It was found that choosing an appropriate step size is not intuitive and the best step size led to a design with a deformation reduction of 30% and a total weight reduction of 35% compared to the initial design.
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摘要 :
The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading...
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The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading conditions while also considering the safety and comfort of the astronauts. One of the critical load cases in spacesuit design is a low-velocity impact (LVI) which may occur due to tool drop and other similar scenarios. The objectives of this work were (a) to create a finite element (FE) model of a component of a spacesuit, (b) validation of the FE model through experiments, (c) creating an optimization framework to design the spacesuit component, and (d) investigate the effect of finite difference step size on the final optimized design. A FE model of a plate was created to represent a part of the spacesuit's hard upper torso (HUT), which is made of a sandwich structure with S2 glass fiber composite (outer layers) and carbon fiber composite (core) materials. The FE model was used to simulate the nonlinear LVI response of the plate using MSC Nastran and were validated against the displacement and contact force history obtained from the LVI experiment using the Instron Impact Test instrument. Further, the sandwich plate was optimized for an impact load case with sizing variables (thickness and ply orientation) and shape variables (length and width) using quadratic, sinusoidal and Hicks-Henne bump shape function. The objective was to minimize weight while being subjected to displacement or stress constraints. The effect of the finite difference step size variation on the shape optimization of the plate was studied. It was found that choosing an appropriate step size is not intuitive and the best step size led to a design with a deformation reduction of 30% and a total weight reduction of 35% compared to the initial design.
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This paper presents Hardware-in-the-Loop (HIL) simulation results of a novel configuration for guidance and tracking control laws for unmanned air vehicles (UAV). The proposed adaptive system is based on an extended non-linear dyn...
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This paper presents Hardware-in-the-Loop (HIL) simulation results of a novel configuration for guidance and tracking control laws for unmanned air vehicles (UAV). The proposed adaptive system is based on an extended non-linear dynamic inversion (NLDI) approach augmented with an artificial immune system mechanism that relies on a direct compensation inspired primarily by the biological immune system response. The implementation of the control laws is illustrated through HIL simulation using a mathematical model of an UAV research platform developed at Embry-Riddle Aeronautical University (ERAU) to support the design, testing and validation of bio-inspired fault tolerant adaptive control algorithms. The main objective of the control laws is to minimize forward, lateral, and vertical distances with respect to a desired trajectory, and maintain stability and adequate performance in the presence of sub-system failures. The performance of the control laws is evaluated during autonomous flight in terms of trajectory tracking errors, real-time execution on board the flight computer, and control activity at nominal and abnormal conditions. The results obtained with the ERAU-UAV HIL environment show that for all cases investigated the extended NLDI approach augmented with the immunity-based mechanism has desirable fault tolerant capabilities and is reliable for in-flight testing operation as a next step towards the validation and verification of this adaptive configuration.
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摘要 :
This paper presents Hardware-in-the-Loop (HIL) simulation results of a novel configuration for guidance and tracking control laws for unmanned air vehicles (UAV). The proposed adaptive system is based on an extended non-linear dyn...
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This paper presents Hardware-in-the-Loop (HIL) simulation results of a novel configuration for guidance and tracking control laws for unmanned air vehicles (UAV). The proposed adaptive system is based on an extended non-linear dynamic inversion (NLDI) approach augmented with an artificial immune system mechanism that relies on a direct compensation inspired primarily by the biological immune system response. The implementation of the control laws is illustrated through HIL simulation using a mathematical model of an UAV research platform developed at Embry-Riddle Aeronautical University (ERAU) to support the design, testing and validation of bio-inspired fault tolerant adaptive control algorithms. The main objective of the control laws is to minimize forward, lateral, and vertical distances with respect to a desired trajectory, and maintain stability and adequate performance in the presence of sub-system failures. The performance of the control laws is evaluated during autonomous flight in terms of trajectory tracking errors, real-time execution on board the flight computer, and control activity at nominal and abnormal conditions. The results obtained with the ERAU-UAV HIL environment show that for all cases investigated the extended NLDI approach augmented with the immunity-based mechanism has desirable fault tolerant capabilities and is reliable for in-flight testing operation as a next step towards the validation and verification of this adaptive configuration.
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Despite advancements made in computational and experimental analysis approaches, achieving successful store separation from rotorcraft remains a highly rigorous task. Wind tunnel-based approaches for store separation modeling larg...
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Despite advancements made in computational and experimental analysis approaches, achieving successful store separation from rotorcraft remains a highly rigorous task. Wind tunnel-based approaches for store separation modeling largely remain infeasible due to the challenges associated with scaling store wake interactions. Furthermore, while high-fidelity computational fluid dynamics (CFD) approaches are capable of closely matching rotorcraft flight test, the high computational expense of these approaches greatly limits the total number of CFD simulations which can be run. However, even with this sparse sampling obtained through CFD potentially terabytes of high-fidelity data is still generated for the flow field. The objective of this study is to determine the feasibility of leveraging this data for the derivation of meaningful surrogate models to the topic of rotorcraft store separation. In this study, two surrogate modeling approaches will be investigated for their ability to predict store surface pressure distributions as a store is launched from a rotorcraft in hover. To generate these surrogate models, three CFD simulations are completed while varying the propulsive force assigned to the store. The CFD simulations were completed using the High-Performance Computing Modernization Program Computational Research and Engineering Acquisition Tools and Environments Air Vehicles (HPCMP CREATE™-AV) Helios code. Once the surrogate models had been generated, an additional CFD simulation with a new propulsive force was assigned to the store. The results of this validation indicated that while the POD surrogate model struggled to provide detailed predictions of store-distributed loads, mean load variations could be modeled well. Results further indicated that through leveraging the CNN-based surrogate model, a significant improvement in distributed load modeling could be obtained. It was further identified that once distributed loads were integrated both POD and CNN-based surrogate models provided a viable path for the generation of a trajectory prediction-based surrogate model for rotorcraft applications. Both POD and CNN-based surrogate models provided significantly reduced computational costs. For each rotorcraft store separation CFD simulation, the computational cost required 10 days of simulation time across 880 CPU cores. While using the surrogate model, comparable predictions could be produced in under three minutes on a single core.
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The integration of UAS into the National Airspace, although imminent, still presents several technological challenges. Before a sucessful integration can occur, it is necessary to demonstrate different technologies in traffic dete...
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The integration of UAS into the National Airspace, although imminent, still presents several technological challenges. Before a sucessful integration can occur, it is necessary to demonstrate different technologies in traffic detection, traffic avoidance, and communications, as well as in the integration of those technologies as a single unit. For this purpose, NASA developed its UAS Airspace Operation Challenge; a Centennial Challenge aimed at the demonstration of these technologies. The challenge consists of developing a UAS solution that can navigate autonomously while detecting and avoiding traffic using ADS-B signals. Embry-Riddle Aeronautical Univeristy developed an entry to this challenge: a UAS consisting of a surrogate UAV, a ground station, and a data link. The traffic detection challenges are addressed by processing images collected from an array of cameras mounted in the wingtips, while the avoidance challenges are addressed with a series of path planning algorithms. For communication, a ground station was built and equipped with a data link for monitoring the aircraft's systems. The individual components were tested sucessfully, but flight test of the integrated unit is still in progress. The challenge was cancelled, but Embry-Riddle's entry remains a valuable asset for UAS integration technology.
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摘要 :
The integration of UAS into the National Airspace, although imminent, still presents several technological challenges. Before a sucessful integration can occur, it is necessary to demonstrate different technologies in traffic dete...
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The integration of UAS into the National Airspace, although imminent, still presents several technological challenges. Before a sucessful integration can occur, it is necessary to demonstrate different technologies in traffic detection, traffic avoidance, and communications, as well as in the integration of those technologies as a single unit. For this purpose, NASA developed its UAS Airspace Operation Challenge; a Centennial Challenge aimed at the demonstration of these technologies. The challenge consists of developing a UAS solution that can navigate autonomously while detecting and avoiding traffic using ADS-B signals. Embry-Riddle Aeronautical Univeristy developed an entry to this challenge: a UAS consisting of a surrogate UAV, a ground station, and a data link. The traffic detection challenges are addressed by processing images collected from an array of cameras mounted in the wingtips, while the avoidance challenges are addressed with a series of path planning algorithms. For communication, a ground station was built and equipped with a data link for monitoring the aircraft's systems. The individual components were tested sucessfully, but flight test of the integrated unit is still in progress. The challenge was cancelled, but Embry-Riddle's entry remains a valuable asset for UAS integration technology.
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