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Finite element model tuning using automated structural optimization system software

AIAA JOURNAL 1996年第2期34卷 392-399页

作者： Cobb, RG Canfield, RA Liebst, BS U.S. Air Force Institute of Technology Wright-Patterson Air Force Base Ohio 45433-7765

A method of adjusting analytical finite element models to measured data is presented. The algorithm uses a mathematical optimization strategy to minimize deviations between measured and analytical modal frequencies and partial mode shapes. A mode tracking algorithm is used to identify and account for mode switching during the optimization process. The algorithm was successfully implemented using the Automated Structural Optimization System Software. Experimental results are presented for tuning a lightly damped 6-m flexible frame structure. The results demonstrate excellent agreement between the tuned model and measured data and illustrate the importance of off-nominal validation before accepting a model for simulation purposes.

关键词： Structural Optimization Finite Element Formulation Mathematical Optimization track algorithm Trusses Elastic Properties Accelerometer Longerons Computing Frequency Response Functions

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Consideration of Wear at High Velocities Using a Hydrocode

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AIAA JOURNAL 2012年第3期50卷 746-751页

作者： Palazotto, Anthony Meador, Stephen USAF Inst Technol Dept Aeronaut & Astronaut Wright Patterson AFB OH 45433 USA

The article offers information on the Holloman High Speed Test track (HHSTT) that performs a variety of tests at high velocities by using rocket sled system. It discusses wear mechanisms and the conclusions of metallu... 详细信息

关键词： Stress Strain Curve Air Force Research Laboratory Finite Element Analysis Numerical Modeling Viscoplasticity Conservation of Mass track algorithm Air Force Base Flight Testing Kinetic Energy

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BEARINGS-ONLY trackING - A HYBRID COORDINATE SYSTEM APPROACH

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1994年第3期17卷 451-457页

作者： GROSSMAN, W Madison Guidance Navigation and Control Yorktown Heights New York 10598

In this paper a bearings-only tracking algorithm is described. The algorithm is an extended Kalman filter (EKF) which combines the linear-in-state properties of the Cartesian state variable definition with the linear-in-measurement properties of the modified polar (MP) state variable definition. This hybrid approach employs the Cartesian system for state and state covariance extrapolation and employs the MP system for state and state covariance updating. Accurate state and state covariance extrapolation is achieved without numerical integration. The filter equations of this EKF are, furthermore, derived using a new line-of-sight algebra which yields equations which are nonlinear algebraic rather than transcendental. This new formulation obviates the need for real-time calculation of inverse trigonometric function and allows for the straightforward derivation of the three-dimensional problem. In comparison to previous formulations, this approach allows for easier manipulation of the filter equations and provides for greater insight into bearings-only tracking problem.

关键词： Extended Kalman Filter Numerical Integration track algorithm Monte Carlo Simulation Modern Control Theory Linear Mapping Gaussian Process Cartesian Coordinate System Spacecraft Attitude Signal Processing

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Numerical analysis of double-diffusive convection/solidification under g-jitter/magnetic fields

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2003年第2期17卷 199-209页

作者： Li, K Li, BQ de Groh, HC Washington State Univ Sch Mech & Mat Engn Pullman WA 99164 USA NASA John H Glenn Res Ctr Cleveland OH 44135 USA

A finite element model is presented for the g-fitter induced double-diffusive convection and solidification phenomena with and without the presence of magnetic fields in an Sn-doped Bi crystal growth system planned for space experiments. The model is developed based on the deforming finite element formulation with the penalty formulation for pressure approximation. An isothermal front tracking algorithm is used to predict the solid-liquid interface. Extensive numerical simulations are carried out and parameters studied include the solute concentration dependent melting temperature and magnetic field strength under both steady state and g-fitter conditions. Both synthesized g-fitter and real g-fitter data taken from space flights are used. Computed results show that the concentration effects on interface morphology must be considered for an accurate prediction of solidification interface morphology, and g-fitter can induce significant connective flows in the liquid pool, which, in turn, cause solute concentration nonuniformity during the space crystal growth. The use of an applied magnetic field can be effective in suppressing the deleterious g-fitter induced convection and solute nonuniformity and their effects on solidification.

关键词： Double Diffusive Convection Numerical Stability Thermal Convection Numerical Simulation Space Experiments Magnetic Fields Solidification track algorithm Thermal Boundary Condition Microgravity

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Novel method for identification of aircraft trajectories in three-dimensional space

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第6期23卷 1021-1029页

作者： Korgul, A Mil Univ Technol PL-01489 Warsaw Poland

In this paper a novel method for identification of aircraft trajectories in three-dimensional space is considered. The differential equations of the vector held of an aircraft's velocity are presented and analyzed. The inverted approximation method is proposed for estimating the smooth trajectories from the discrete and sparse past position readings of an aircraft in order to identify the state variables and kinematic parameters of an aircraft's movement. The linear and vectorizable procedure as well as its time delay neural network implementation for the purpose of a trajectory recognition Is outlined. The performance of this method is assessed in the simulation of maneuvering target interception.

关键词： Aircraft Trajectory Time Delay Neural Network track algorithm Model Aircraft Mathematical Models Very Large Scale Integration Aerodynamic Drag Proportional Navigation Singular Perturbation Numerical Integration

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Reactive Collision Avoidance Using Nonlinear Geometric and Differential Geometric Guidance

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2011年第1期34卷 303-311页

作者： Mujumdar, Anusha Padhi, Radhakant Indian Inst Sci Dept Aerosp Engn Bangalore 560012 Karnataka India

Using the philosophy of "collision cone" and "DI," two novel guidance strategies, named as NGG and DGG, are proposed in this Note for reactive collision avoidance of UA Vs. Appropriate correlation among them has also been derived. For additional safety, a sphere-tracking algorithm is also proposed in this Note which guides the vehicle along the surface of an obstacle’s safety sphere when a brief violation occurs after reaching the aiming point on its surface. Incorporating the philosophy of "PCA," the guidance laws have also been made applicable for moving obstacles as well. The numerical simulation results are quite promising. To be more realistic, simulation studies have also been carried out in presence of autopilot lags and, if the lag is large, an innovative lag compensation logic has also been proposed. The numerical simulation results are quite promising. Even though the main aim of this Note is collision avoidance of UA Vs, the core idea is inspired from the missile guidance literature. Hence, other potential applications of the proposed guidance laws would include guidance of missiles. In such applications, the predicted target position can serve as the aiming point towards which the velocity vector of the missile should be aligned.

关键词： Autopilot Guidance Laws track algorithm Model Predictive Control Prediction algorithms Numerical Simulation Artificial Potential Fields Missile Guidance Path Planning Proportional Navigation

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IMAGE FUSION algorithmS FOR trackING MANEUVERING TARGETS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第1期15卷 175-184页

作者： HUTCHINS, RG SWORDER, DD UNIV CALIF SAN DIEGO DEPT APPL MECH & ENGN SCILA JOLLACA 92093

Evasive target maneuvers create problems for traditional state-space filtering and tracking algorithms because maneuver accelerations are frequently abrupt and are not well modeled by wideband noise processes. Earlier work has suggested the use of an imaging sensor to determine target orientation, from which the likely direction of a maneuver acceleration can be inferred. This paper examines the issues that arise when an image-based orientation measurement is used in conjunction with a traditional sensor/filter for enhanced detection of maneuvering accelerations and for prediction of target location.

关键词： Sensor Technology track algorithm Image Fusion Extended Kalman Filter Nonlinear Filter Brownian Motion Interacting Multiple Model Monte Carlo Simulation Fixed Wing Aircraft Missile Guidance and Control

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Probabilistic Data Association for Orbital-Element Estimation Using Multistage Expectation-Maximization

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2021年第5期18卷 250-268页

作者： Bernstein, Jason Lawrence Livermore Natl Lab Computat Engn Div Livermore CA 94550 USA

tracking space objects is important for managing space traffic and predicting collisions, but is difficult in part due to data association and orbit model uncertainty. Expectation-maximization (EM) is a commonly used tracking method that has not been widely considered for tracking space objects. The technique consists of iteratively computing data association probabilities with a set of current element estimates, and updating estimates of the elements by solving a nonlinear weighted least-squares regression problem where the weights are the data association probabilities. This paper demonstrates the use of EM for probabilistic data association and orbital-element estimation by applying the technique to simulated data from two angles-only tracking scenarios. In both scenarios, EM provides correct data associations and accurate maximum likelihood estimates of orbital elements. One scenario considers tracking a single object in clutter and quantifies the improvement of the orbital-element estimates and data associations as the detection probability increases. However, standard application of EM requires knowing the number of objects or may fail when a large number of objects are present. To address these issues, this paper employs a multistage version of EM that is applicable when there are a large and possibly unknown number of objects.

关键词： Orbital Elements Computing Orbit Determination Kepler's Equation Linkages Probability Distribution Gaussian Mixture Models track algorithm Earth Space Situational Awareness

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Unscented-Kalman-Filter-Based Multitarget tracking algorithms for Airborne Surveillance Application

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2016年第9期39卷 1949-1966页

作者： Roy, Anirban Mitra, Debjani Airbus Grp Airbus Def & Space Air Vehicle Syst Bangalore 560016 Karnataka India Indian Sch Mines Elect Engn Dhanbad 826004 Bihar India

This paper addresses the problem of multitarget tracking for aerial surveillance application. An infrared search and track sensor, mounted on an unmanned platform, is deployed for tracking and provides three-dimensional bearing and elevation angle measurements immersed with clutters. A Gaussian-mixture/probability-hypothesis-density multitarget tracker using an unscented Kalman filter is proposed to estimate target trajectories. A new closed-loop formulation of the unscented-Kalman-filter/Gaussian-mixture/probability hypothesis density is derived using fundamental properties of nonlinear Bayesian filtering. A tag management procedure to maintain individual track identity is also discussed. The performance of the unscented-Kalman-filter/Gaussian-mixture/probability hypothesis density is compared with seven data-association-based multitarget tracking algorithms, such as 1)the suboptimal nearest neighbor, 2)the global nearest neighbor using Munkres optimal assignment method, 3)the global nearest neighbor with the Jonker-Volgenant-Castanon assignment technique, 4)the multihypothesis tracking using N-best feasible solutions, 5)probabilistic data association, 6)nearest-neighbor probabilistic data association, and 7)K-nearest-neighbor probabilistic data association. These algorithms are computed using the unscented Kalman filter and follow a track-oriented approach. Simulation results reveal that the unscented-Kalman-filter/Gaussian-mixture/probability hypothesis density algorithm has superior performance over conventional data-association methods in terms of cardinality accuracy and robustness.

关键词： track algorithm Unscented Kalman Filter Infrared Sensors Infrared Search and track Closed Loop Aerial Surveillance Application UAV Airspeed Earth Probability Density Functions

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Global positioning system integer ambiguity resolution without attitude knowledge

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1999年第2期22卷 212-218页

作者： Crassidis, JL Markley, FL Lightsey, EG Texas A&M Univ Dept Aerosp Engn College Stn TX 77843 USA NASA Goddard Space Flight Ctr Guidance Navigat & Control Ctr GNOC Syst Engn Branch Greenbelt MD 20771 USA

In this paper, a new motion-based algorithm for global positioning system integer ambiguity resolution is derived. The algorithm represents the global positioning system sightline vectors in the body frame as the sum of two vectors, one depending on the phase measurements and the other on the unknown integers. The vector containing the integer phases is found using a procedure developed to solve for magnetometer biases. In addition to a batch solution, this paper also provides a sequential estimate, so that a suitable stopping condition can be found during the vehicle motion. The new algorithm has several advantages: it does not require an a priori estimate of the vehicle's attitude;it provides an inherent integrity check using a covariance-type expression;and it can sequentially estimate the ambiguities during the vehicle motion. Its only disadvantage is that it requires at least three noncoplanar baselines, The performance of the new algorithm is tested on a dynamic hardware simulator.

关键词： GPS Magnetometers NASA Goddard Space Flight Center GPS Satellites GPS Receivers Earth Spacecraft Antennas Spacecraft Attitude track algorithm Gaussian Process

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