An Investigation of the Impact of Aerodynamic Model Fidelity on Close-In Combat Effectiveness Prediction in Piloted Simulation

Abstract Horizontally oriented plates in clouds generate a sharp specular reflectance signal in the glint direction, often referred to as “subsun.” This signal (amplitude and width) may be used to analyze the relative area fraction of oriented plates in the cloud-top layer and their characteristic tilt angle to the horizontal. Use is made of spaceborne measurements from the Polarization and Directionality of the Earth Reflectances (POLDER) instrument to provide a statistical analysis of these parameters. More than half of the clouds show a detectable maximum reflectance in the glint direction, although this maximum may be rather faint. The typical effective fraction (area weighted) of oriented plates in clouds lies between 10−3 and 10−2. For those oriented plates, the characteristic tilt angle is less than 1° in most cases. These low fractions imply that the impact of oriented plates on the cloud albedo is insignificant. The largest proportion of clouds with horizontally oriented plates is found in the range 500– 700 hPa, in agreement with typical in situ observation of plates in clouds. A simple aerodynamic model is proposed that accounts for the orienting torque of the flow as the plate falls under its own gravity and the disorienting effects of Brownian motion and atmospheric turbulence. The model indicates that the horizontal plate diameters are in the range 0.1 to a few millimeters. For such sizes, Brownian forces have a negligible impact on the plate orientation. On the other hand, typical levels of atmospheric turbulence lead to tilt angles that are similar to those estimated from the glint observation.

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Exploring the Impact of Model Fidelity Through Interactive Visualizations for System of Systems

10.2514/6.2022-1467 ◽

2022 ◽

Author(s):

Sofia Schön ◽

Ludvig Knöös Franzén ◽

Carina Marcus ◽

Kristian Amadori ◽

Christopher Jouannet ◽

...

Keyword(s):

System Of Systems ◽

Model Fidelity ◽

Interactive Visualizations ◽

The Impact

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Effect of Model Element Fidelity Within a Complex Function-Based Behavioral Model

Volume 3: 28th Computers and Information in Engineering Conference, Parts A and B ◽

10.1115/detc2008-49355 ◽

2008 ◽

Cited By ~ 2

Author(s):

Ryan S. Hutcheson ◽

Daniel A. McAdams ◽

Robert B. Stone ◽

Irem Y. Tumer

Keyword(s):

Complex Function ◽

Behavioral Model ◽

Design Tool ◽

Prior Work ◽

Behavioral Models ◽

Early Design ◽

Formula Sae ◽

Model Fidelity ◽

Performance Predictions ◽

The Impact

The Function-based Behavioral Modeling (FBBM) design tool was introduced in prior work as a means of using formal functional modeling as the foundation for creating detailed mathematical models of system behavior. The overall objective of this work is to create a framework for partitioning modeling efforts into functional elements and promoting model storage and re-use through the use of functional models. In prior work, the FBBM method was introduced to model the complete vehicle dynamics of a Formula SAE racecar, highlighting the representation of functionality and the development of behavioral models. The objective of the work presented in the current paper is to demonstrate the ability to incorporate models of varying fidelity within a function-based behavioral model of a complex system. Additionally, the impact of model fidelity on the model’s predictions is addressed. A previously developed model is used as a foundation for developing the necessary new models and illustrating the impact of model fidelity on performance predictions when selecting a tire during early design. The results illustrate that the FBBM framework allows models of varying fidelity to be quickly made and their effect on predicted performance to be measured in order to assist critical early design choices.

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Lifting Line Free Wake Vortex Filament Method for the Evaluation of Floating Offshore Wind Turbines: First Step — Validation for Fixed Wind Turbines

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7540 ◽

2019 ◽

Author(s):

Raquel Martín-San-Román ◽

José Azcona-Armendáriz ◽

Alvaro Cuerva-Tejero

Keyword(s):

Wind Turbines ◽

Vortex Filament ◽

Offshore Wind ◽

Critical Parameters ◽

Aerodynamic Model ◽

Floating Offshore Wind Turbines ◽

Free Wake ◽

The Impact ◽

Lifting Line ◽

Vortex Filament Method

Abstract An in-house computational tool, called MIST, has been developed to improve the accuracy of the aerodynamic loads predictions of floating wind turbines. MIST has an aerodynamic module based on a Free Vortex filament Method (FVM) for the wake combined with a Lifting Line (LL) model for the blades. This aerodynamic model has been validated, in this first instance, for an onshore configuration against well known experimental data. Different options for the critical parameters of the code have been analyzed to get a deeper understanding of the impact of certain assumptions of this kind of models.

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The Role of Model Fidelity in Model Predictive Control Based Hazard Avoidance in Unmanned Ground Vehicles Using LIDAR Sensors

Volume 3: Nonlinear Estimation and Control; Optimization and Optimal Control; Piezoelectric Actuation and Nanoscale Control; Robotics and Manipulators; Sensing; System Identification (Estimation for Automotive Applications, Modeling, Therapeutic Control in Bio-Systems); Variable Structure/Sliding-Mode Control; Vehicles and Human Robotics; Vehicle Dynamics and Control; Vehicle Path Planning and Collision Avoidance; Vibrational and Mechanical Systems; Wind Energy Systems and Control ◽

10.1115/dscc2013-4021 ◽

2013 ◽

Cited By ~ 18

Author(s):

Jiechao Liu ◽

Paramsothy Jayakumar ◽

James L. Overholt ◽

Jeffrey L. Stein ◽

Tulga Ersal

Keyword(s):

Model Predictive Control ◽

Predictive Control ◽

Vehicle Dynamics ◽

High Fidelity ◽

Unmanned Ground Vehicles ◽

Ground Vehicles ◽

Model Fidelity ◽

Hazard Avoidance ◽

The Impact

Unmanned ground vehicles (UGVs) are gaining importance and finding increased utility in both military and commercial applications. Although earlier UGV platforms were typically exclusively small ground robots, recent efforts started targeting passenger vehicle and larger size platforms. Due to their size and speed, these platforms have significantly different dynamics than small robots, and therefore the existing hazard avoidance algorithms, which were developed for small robots, may not deliver the desired performance. The goal of this paper is to present the first steps towards a model predictive control (MPC) based hazard avoidance algorithm for large UGVs that accounts for the vehicle dynamics through high fidelity models and uses only local information about the environment as provided by the onboard sensors. Specifically, the paper presents the MPC formulation for hazard avoidance using a light detection and ranging (LIDAR) sensor and applies it to a case study to investigate the impact of model fidelity on the performance of the algorithm, where performance is measured mainly by the time to reach the target point. Towards this end, the case study compares a 2 degrees-of-freedom (DoF) vehicle dynamics representation to a 14 DoF representation as the model used in MPC. The results show that the 2 DoF model can perform comparable to the 14 DoF model if the safe steering range is established using the 14 DoF model rather than the 2 DoF model itself. The conclusion is that high fidelity models are needed to push autonomous vehicles to their limits to increase their performance, but simulating the high fidelity models online within the MPC may not be as critical as using them to establish the safe control input limits.

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Feature Variation and its Impact on Structural Acoustic Response Predictions

Journal of Vibration and Acoustics ◽

10.1115/1.1523072 ◽

2003 ◽

Vol 125 (1) ◽

pp. 31-38

Author(s):

Kenneth A. Cunefare

Keyword(s):

Acoustic Power ◽

Reference State ◽

Acoustic Response ◽

Model Fidelity ◽

Quantity Of Interest ◽

Resonance Frequencies ◽

Quadratic Response ◽

Constant Bandwidth ◽

Bandwidth Analysis ◽

The Impact

This paper presents a screening technique to assess the impact on model fidelity introduced by variations in the properties or positions of features in harmonically forced fluid-loaded structural acoustic models. The perspective taken is one of knowledge of a reference state, with a desire to determine the impact on the total radiated acoustic power due to perturbations in the reference state. Such perturbations change the predicted resonance frequencies of a structure under consideration, and hence, change the predicted response amplitudes. The method uses a single degree of freedom response model in the local region of each fluid-loaded resonance, coupled with eigenvalue sensitivities or variations, to estimate the perturbation impact. The perturbation is scaled by the degree to which each given mode participates in the response quantity of interest. The SDOF model yields results that indicate that proportional bandwidth analysis will be less sensitive to perturbation than constant bandwidth analysis. This is demonstrated through comparison of a constant bandwidth analysis and a 1/3 octave analysis applied to the same system. Elements of the analysis method are not necessarily restricted to model perturbations nor acoustic power, rather they may be used to assess the perturbation of any quadratic response quantity of interest due to changes in resonance frequency.

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