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Positioning Algorithm for Autonomous Thermal Soaring

JOURNAL OF AIRCRAFT 2012年第2期49卷 472-482页

作者： Akhtar, Naseem Cooke, Alastair K. Whidborne, James F. Cranfield Univ Dept Aerosp Sci Sch Engn Cranfield MK43 0AL Beds England

A positioning algorithm for autonomous thermal soaring is proposed and tested in a simulation environment. The Carmichael model was used for the characterization of thermals of varying strengths, and the values of bank angle and airspeed required to extract maximum energy were derived from an analysis of sailplane performance. Two-dimensional strip theory was used within a high-fidelity six-degree-of-freedom model to estimate the interaction of the aircraft with updrafts caused by thermal activity, and a control system, based on classical theory, was designed to position the sailplane for optimum energy extraction. The need for a better algorithm is shown, and improvements were achieved by using aileron deflection information to determine the orientation of the thermal center relative to the sailplane. Energy extraction is demonstrated in terms of altitude gained, and the algorithm's ability to position the sailplane is shown in a number of scenarios.

关键词： Air Vehicle Aerodynamic Center Airspeed Ailerons Six Degree of Freedom Control Systems algorithms ability Lift Coefficient Thermal Modeling Vortex Rings

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Multiple Horizon Model Predictive Flight Control

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2014年第3期37卷 946-951页

作者： Medagoda, Eran D. B. Gibbens, Peter W. Univ Sydney Sch Aerosp Mech & Mechatron Engn Sydney NSW 2006 Australia

No abstract available.

关键词： Flight Control System Model Predictive Control Airspeed Phugoid Elevator Optimal Control Multiple Input Multiple Output Systems Quadratic Programming Spacecraft Control algorithms ability

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Instantaneous Quadratic Power-Optimal Attitude Tracking with N Control Moment Gyroscopes

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2017年第3期40卷 701-708页

作者： Lubey, Daniel P. Schaub, Hanspeter Univ Colorado Aerosp Engn Sci Boulder CO 80309 USA

A new globally asymptotically stable tracking control policy that instantaneously optimized a power analogous cost for systems with N control moment gyroscopes (CMGs). This development fills a hole by providing an instantaneous power-optimal infinite-horizon control policy for N CMG systems that is computationally simple to implement for real-time applications. The method developed may be solved via an iterative approach when the system has more than four CMGs, but for systems with four CMGs, an analytical solution was derived. Through a numerical simulation, a comparison between the performance of this power-optimal policy and a more standard minimum norm solution was made. This revealed that both control policies accurately track a moving reference and that the optimal power policy minimizes power usage in the system, with the ability to yield drastic energy savings over the course of an entire maneuver. Because these control policies are optimized instantaneously, there is no guarantee that the power-optimal solution will outperform the minimum norm solution for a given set of gains since they provide convergence via two separate state trajectories.

关键词： Control Moment Gyroscope Attitude Tracking Lyapunov Analysis Lagrange Multipliers Optimal Control Energy Storage Numerical Simulation Reaction Wheels Propellant algorithms ability

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Synthetic-Waypoint Guidance Algorithm for Following a Desired Flight Trajectory

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2010年第2期33卷 601-606页

作者： Medagoda, Eran D. B. Gibbens, Peter W. Univ Sydney Sch Aerosp Mech & Mechatron Engn Sydney NSW 2126 Australia

THE development of aircraft guidance, navigation, and control systems has been a long-standing research area. Numerous methods relating to the enhancement of aircraft performance under various mission parameters have been developed in response to a need for more reliable and robust guidance systems. Current guidance systems applied to commercial, civilian, and unmanned aircraft rely on the knowledge of a flight path, specified by waypoints located in inertial space. Most missions are considered successful when the vehicle reaches the designated waypoint at which new commands are issued to the vehicle to proceed to the next waypoint. Two common types of conventional aircraft guidance are the direct-to-waypoint (DTW) and track-to-waypoint (TTW) methods in relation to path-following between designated waypoints. The DTW method simply issues heading commands to the vehicle based on the angular difference between the waypoint and vehicle. When the vehicle reaches the waypoint, the control system issues a new command to guide the aircraft to the next waypoint. The TTW method aims to follow me track between waypoints. In this guidance method the control system aims to minimize the lateral offset between the prescribed flight path and the aircraft's position, issuing heading commands that return the vehicle to the nominal flight path. The track method therefore places the additional constraint on a flight path that the vehicle must follow in order to reach the waypoint, rather than simply reaching the waypoint. However, both methods are far from optimal. This is evident in how the aircraft transitions between flight paths after reaching a waypoint During these flight-path transitions, the aircraft will often overshoot the desired flight path to correct its track, particularly when the flight-path transition angle is acute. Various control strategies have been investigated to alleviate or minimize flight-path deviations. Such strategies include applying modern control method

关键词： Guidance algorithms Flight Trajectory Linear Quadratic Regulator True Airspeed Control Guidance Aircraft Performance Pursuit Guidance Missile Guidance Aircraft Trajectory algorithms ability

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Advisory Algorithm for Scheduling Open Sectors, Operating Positions, and Workstations

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2014年第4期37卷 1158-1169页

作者： Bloem, Michael Drew, Michael Lai, Chok Fung Bilimoria, Karl D. NASA Ames Res Ctr Syst Modeling & Optimizat Branch Moffett Field CA 94035 USA Univ Calif Santa Cruz Syst Modeling & Optimizat Branch Moffett Field CA 94035 USA NASA Ames Res Ctr Flight Trajectory Dynam & Controls Branch Moffett Field CA 94035 USA

Air traffic controller supervisors configure available sector, operating position, and workstation resources to safely and efficiently control air traffic in a region of airspace. In this paper, an algorithm for assisting supervisors with this task is described and demonstrated on two example problem instances. The algorithm produces configuration-schedule advisories that minimize a cost. The cost is a weighted sum of two competing costs: one penalizing mismatches between configurations and predicted air traffic and another penalizing the effort associated with changing configurations. The problem considered by the algorithm is a shortest-path problem. The parameter determining the relative importance of the two competing costs is tuned by comparing historical configurations with corresponding algorithm advisories. Furthermore, some operationally-meaningful metrics are computed with the results of simulations of the algorithm for various values of this parameter. Two example problem instances for which appropriate configuration advisories are obvious were designed to illustrate characteristics of the algorithm. The results demonstrate how the algorithm suggests advisories that appropriately use changes in airspace configurations and changes in the number of operating positions allocated to each open sector. The results also demonstrate how the advisories suggest appropriate times for configuration changes.

关键词： Special Use Airspace Air Route Traffic Control Center RADAR Federal Aviation Administration Air Traffic Management algorithms ability

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Simulation of a moving elastic beam using Hamilton's weak principle

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AIAA JOURNAL 2007年第2期45卷 471-476页

作者： Leigh, Elliott J. Kunz, Donald L. USAF Inst Technol Dept Aeronaut & Astronaut Wright Patterson AFB OH 45433 USA

A proof-of-concept algorithm for calculating the general motion of elastic beams in the context of a multibody system analysis has been developed and validated. The governing equations for moving elastic beams with closed cross sections have been formulated using Hamilton's law of varying action. They are then discretized with a mixed space-time finite element scheme, which results in a system of nonlinear algebraic equations. These equations are solved using unconstrained optimization techniques, thereby obtaining steady-state and time-accurate solutions for linear and nonlinear structural dynamics problems. Solutions obtained for a variety of static, steady-state, and transient test cases have demonstrated them accuracy of the formulation. Illustrative examples, including the cantilever elastica problem, rotation of a beam at a constant angular velocity, and prescribed flapping motion of a beam, are presented.

关键词： Finite Element Formulation Cantilever Beam Multibody Dynamics Nonlinear Structural Dynamics Flapping Frequency Young's Modulus Bending Moment Lagrange Multipliers Boundary Value Problems algorithms ability

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Adaptive Control of Precision Guided Airdrop Systems with Highly Uncertain Dynamics

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2018年第5期41卷 1025-1035页

作者： Cacan, Martin R. Costello, Mark Georgia Inst Technol Woodruff Sch Mech Engn Ctr Adv Machine Mobil Atlanta GA 30322 USA Georgia Inst Technol Auton Guggenheim Sch Aerosp Engn Atlanta GA 30322 USA

The bulk of research in the field of precision guided airdrop systems has focused on improving landing accuracy in the presence of atmospheric winds that can exceed vehicle airspeed. One important challenge of parafoil systems is their highly uncertain flight dynamic behavior and control response, which can result from canopy degradation or an offnominal inflation event. This significantly impacts the ability to reach the target and can often lead to very large miss distances. This work addresses guided airdrop system model uncertainty with a novel combined direct and indirect adaptive control strategy to quickly characterize vehicle dynamics and lateral control sensitivity in flight. Extensive simulation and experimental flight testing indicate that the proposed adaptive algorithm is capable of high-accuracy landing in a large variety of degraded conditions, including unknown nonlinear changes in control sensitivity as well as control reversals. In comparison, current industry standard algorithms experience over an order of magnitude decrease in accuracy when tested under identical scenarios.

关键词： Adaptive Control Algorithm Parafoil Experimental Flight Test Airspeed Control Reversal Adaptive Algorithm Navigation Algorithm GPS Multiple Input Multiple Output algorithms ability

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Health Monitoring of Aerospace Structures via Dynamic Strain Measurements: An Experimental Demonstration

Health Monitoring of Aerospace Structures via Dynamic Strain...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech)

作者： Martins, B. L. Kosmatka, J. B. Univ Calif San Diego Dept Mech & Aerosp Engn 9500 Gilman DrMail Code 0085 La Jolla CA 92093 USA Univ Calif San Diego Dept Struct Engn 9500 Gilman DrMail Code 0085 La Jolla CA 92093 USA

ISBN: (数字)9781624105951

ISBN: (纸本)9781624105951

A methodology has been developed to allow for in-situ structural health monitoring of aerospace vehicles during normal (in flight) operation. The method relies on response only power spectral density measurements derived from a network of fiber optic strain gages. The measured strain power spectral densities are compared to previously correlated finite element models using a residual error function. A developed Bayesian objective function minimizes the system imbalance and in turn provides an estimate of the presence, location, type, and severity of damage within a structural system. The developed algorithm was experimentally demonstrated by studying a pair of cuts collocated along the span of a carbon/epoxy composite testbed. The algorithm was shown to successfully identify the presence of damage and well as provide an estimate of the location, type, and severity of the detected damage. In addition to a damage assessment, a product of the health monitoring algorithm is a correlated finite element model of the structure in the damaged state which was shown to globally represent the dynamic behavior of the testbed.

关键词： Power Spectral Density Structural Health Monitoring Finite Element Modeling Structural System Damage Assessment Structural Response Cantilever Beam algorithms ability Material Properties Bending Vibration

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Geometric Path Following of Underwater Vehicles

Geometric Path Following of Underwater Vehicles

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Rober, Nicholas Cichella, Venanzio Univ Iowa Dept Mech Engn Iowa City IA 52242 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

This paper addresses the problem of guidance and control of underwater vehicles. The overall control architecture is broken into three different functions: path generation, path following, and vehicle autopilot. The path-generation function creates a 3D path based on mission objectives specified by an operator. A point along the path is tracked by the path-following algorithm, which passes pitch and yaw rate commands to the autopilot. The latter adjusts the vehicle's control surfaces to track the angular rate commands. The introduction of a variable called virtual time allows the target point to be adjusted along the path according to a specified control law. The framework for the path-following algorithm is built upon the Special Orthogonal Group SO(3) with several reference frames relating the vehicle, the virtual target, and the global (inertial) coordinate system. A critical component of the path-following algorithm is the construction of a desired reference frame that specifies the ideal orientation of the vehicle. The desired frame features an adjustable parameter that affects the aggressiveness of the controller, offering the ability to easily adjust its performance. The paper provides guaranteed performance bounds of the path-following algorithm and considers actuation limits on the vehicle's angular rates, as well as limited performance of the on-board autopilot.

关键词： Autopilot Control Surfaces Autonomous Underwater Vehicle Unmanned Aerial Vehicle Computational Fluid Dynamics algorithms ability Motion Planning Track Algorithm Wheeled Robot Euler Angles

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Probabilistic Learning of Operator Interest in Surveillance Environments for Online Track Characterization

Probabilistic Learning of Operator Interest in Surveillance ...

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AIAA SciTech Forum

作者： Kravitz, Eli Ray, Hunter M. Conlon, Nicholas Ahmed, Nisar R. Thomas, Ian Szafir, Danielle Albers Univ Colorado Boulder Smead Aerosp Engn Sci Boulder CO 80309 USA Univ Colorado Boulder Dept Comp Sci Boulder CO 80309 USA Univ North Carolina Chapel Hill Dept Comp Sci Chapel Hill NC USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Machine learning models that augment data-intensive human workflows must rely on an understanding of a user's interests and behaviors. By understanding what a user desires, these models can help intuitively prioritize workflow and essential information for decision making, and form the baseline for trusted autonomous systems. This work considers the problem of human interest classification for missile defense surveillance. In this case, users are satellite operators who must prioritize simultaneous processing and characterization of targets across the globe for extended duration while working under strict time and accuracy constraints. Learning human interest in this context is particularly challenging because user interests are generally not static, tracks have a short lifespan, and the user pool is small. Here, we formulated the solution similarly as a binary Bayesian logistic regression problem to classify operator interest in a given candidate track, but with the added complexity of partially observable feature variables and dependencies between these variables. Our approach leverages domain knowledge to instantiate priors on human interest and, using online user interactions with the system, can continuously infer human interest for candidate tracks. We validate our user interest classification algorithm using simulated truth testing across various configurations of expected operator behavior, which overall show that the algorithm can effectively learn relative track interest with minimal training data.

关键词： Satellite Operator Naive Bayes Classifier Missile Defense Autonomous Systems Artificial Intelligence Black Box algorithms ability Monte Carlo Method Computer Vision Geography

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