Gregory D. Sweriduk

New Approach for Modeling, Analysis, and Control of Air Traffic Flow

An Eulerian approach to modeling air traffic flow is advanced. This modeling technique spatially aggregates air traffic to generate models of air traffic flow in a network of interconnected, one-dimensional control volumes. The approach simplifies the problem of characterizing the air traffic flow because the order of the corresponding airspace model depends only on the number of spatial control volumes used to represent the air traffic environment and not on the number of aircraft operating in it. Under a quasi-steady-state assumption, this process results in linear models of the air traffic environment. It is shown that analysis and design methods from linear control theory can be applied to this model to yield useful approaches for characterizing and controlling the air traffic flow.

Integrated Guidance and Control of Moving Mass Actuated Kinetic Warheads

Abstract : Modeling, simulation, and integrated guidance-control of a kinetic warhead utilizing moving- mass actuators are discussed. Moving masses can be used in any speed range both in the atmosphere as well as outside it, as long as there is a force, either aerodynamic or propulsive, acting on the vehicle. Since they are contained entirely within the airframe geometric envelope, and because no mass expulsion is involved, moving-mass actuation technique offers significant advantages over conventional aerodynamic control surfaces and reaction control systems. The present research developed a high fidelity, nine degree-of-freedom simulation model of a kinetic warhead with three moving-mass actuators. This simulation model is used for actuator sizing and in the development of flight control systems. A software package for performing numerical feedback linearization technique is employed for the design of nonlinear flight control systems. Interception of non-maneuvering and weaving targets in both atmospheric and exo-atmospheric conditions are demonstrated.

Computer-Aided Eulerian Air Traffic Flow Modeling and Predictive Control

Eulerian models are used to represent the air traffic environment as traffic flows between interconnected control volumes representing the airspace system. While these models can be manually derived for simple air traffic patterns, computer-based approaches are essential for modeling realistic airspaces involving multiple traffic streams. A computer- aided methodology for deriving large-dimensional Eulerian models of air traffic flow is described here. Starting from the specification of a few airspace parameters, and traffic data, the modeling technique can automatically construct Eulerian models of the airspace. The synthesis of air traffic flow control algorithms using the model predictive control technique in conjunction with these models is given. It is shown that the flow control logic synthesis can be cast as a linear programming problem. The flow control methodology is illustrated using air traffic data over two regions in U.S. airspace.

4D Green Trajectory Design for Terminal Area Operations Using Nonlinear Optimization Techniques

The work under this research deals with the development of a computational framework suitable for the design and analysis of 4D green trajectories for terminal airspace operations. First, a 4D-trajectory-based operational concept for terminal area operation consisting of ground-side automation and flight-deck-side automation is presented. The focus of the current paper is the development of 4D-trajectory design tools as part of the ground-side automation. The paper first identifies aircraft aerodynamic, fuel consumption, emissions, and noise models necessary for trajectory optimization based on open-source data such as the Base of Aircraft DAta (BADA). A numerical trajectory optimization framework is then proposed for the design of 4D-trajectories. The framework is able to accommodate aircraft performance constraints, separation constraints, and airport capacity considerations, and it can model “green” considerations such as fuel & emissions minimization, and noise reduction. The trajectory optimization framework is demonstrated on single and multiple aircraft scenarios. Using parametric optimization approach the paper explores the relationship between the time-of-arrival at runway threshold and the fuel consumption for a B737 aircraft. In the multi-aircraft scenario the paper illustrates the implementation of 3 nmi separation criteria between a pair of aircraft. A companion paper deals with the flight-deck-side automation that tracks the 4D trajectory clearances created by the groundside automation.

Study of Near-Optimal Endurance-Maximizing Periodic Cruise Trajectories

A near -opt imal periodic solution to the maximum -endurance cruise problem is investigated. Point -mass models are developed for different types of aircraft. Energy -state methods are used to determine minimum -fuel climb and maximum -endurance descent schedules in the altitude -airspeed plane, which are then pieced together with transition arcs to form a periodic cruise solution. A trajectory tracking controller is designed to make the point -mass models track the periodic cruise trajectories. The tracking controller is designed using the feedback linearization methodology. Closed -loop simulations are then used to compute the fuel consumption resulting from the use of periodic trajectories. These values are compared to the steady -state, optimal -endurance cruise fuel con sumption values. For an F/A -18 aircraft model, it was found that savings of about 17% could be realized if the engines can be turned off when the aircraft is not on the climb schedule. However, if the throttle cannot be set below flight idle, the periodic cruise trajectory is found to produce worse performance than the steady -state cruise, primarily due to poor specific fuel consumption at idle throttle setting. Simulations with a model of an F -4 in periodic cruise with idealized engine characteristics no n-zero minimum thrott le did show a modest improvement over the steady -state cruise performance, but only by 2.7%.

Concept and Requirements for Airport Surface Conflict Detection and Resolution

The paper deals with the concept and requirement for airport surface Conflict Detection and Resolution (CD&R). The scope of the proposed CD&R concept spans across three different timeframes: (i) near-term (2015), (ii) mid-term (2020), and (iii) far-term (2025). Enabling technologies such as (i) surveillance, (ii) airport surface operations planning automation, (iii) clearance delivery mechanism, (iv) clearance information available to CD&R automation, and (v) flight-deck automation are studied. The paper identifies the functional requirements for the CD&R automation system such as aircraft state estimation module and aircraft trajectory prediction module. Detalied descriptions of the individual algorithms are beyond the scope of the current paper and will be presented in a future paper. However, preliminary closed-loop simulation results obtained with the conflict detection and resolution system are presented.

Process and Software Tools for Generating Airport Models to Support Surface Operation Analyses

In NASA’s NextGen-Airspace Project, the System Level Design, Analysis, and Simulation Tools (SLDAST) Research Focus Area (RFA) has responsibility for developing system-level analysis and simulation tools that can be used to assess concepts and technologies developed by RFAs across several NASA projects. The most prominent assessment product from SLDAST is the Airspace Concept Evaluation System (ACES), which provides simulation capabilities over the whole NAS with details down to airport surface traffic. Among the options in ACES for airport modeling, the most detailed one involves a link/node queuing model which represents the complete layout of the airport surface including all runways, taxiways, ramp area, and gates. This link/node surface model is adequate for assessing various options of surface operations, including trajectory-based operations, an important capability considered for the NextGen transformation. Due to the amount of details, the generation of a link/node surface model for each airport is quite involved. It requires modeling the airport surface layout by geo-registering all important locations on the surface such as gates and runway/taxiway intersections, and connecting the nodes into a network to include all the taxiways, runways, and taxi paths within the ramp area. The resulting link/node data are eventually used in defining a queuing network for simulating the surface operations. As a large number of such models will be required to support simulation of the nation-wide traffic, a modeling process has been developed for generating the model data to ease the effort in developing these surface models. In addition to generating the complex link/node data, the process needs to specify procedures for gate assignment and route planning. A suite of software tools, known as SurfTools, has been developed to support the modeling process by automating the generation of the necessary data files required by the simulation. This paper provides a high-level description of the modeling process, and describes the design and implementation of SurfTools. A companion paper describes in more detail the modeling process, the model data requirements, and how the models are used to support surface-operation simulations.

Modeling Requirements to Support Assessment of NextGen Mid-Term Performance

The Next Generation Air Transportation System (NextGen) Concept of Operations addresses air transportation operations in the 2025 timeframe. Although NextGen is expected to include revolutionary solutions for handling the anticipated increase in demand in the National Airspace System (NAS) in this timeframe, implementation of the new systems and procedures will still have to evolve over time. Assessment of NextGen performance needs to address the target timeframe of 2025, as well as reasonably defined intermediate time points to understand its progression. The FAA has released its NextGen Implementation Plan (NGIP) to address the FAA’s portion of the work needed to realize NextGen, covering the FAA’s plan through the mid-term period of 2018. This NGIP serves as a good source of information to assess the NextGen mid-term performance as a transitional step towards the envisioned 2025-timeframe NextGen. This paper describes a study to establish the mid-term NextGen performance for defining scenarios for analyses of integrated concepts, technologies, and procedures under development in NASA’s Airspace Systems Program amidst projected FAA infrastructure development. The study involves a two-step process: it starts with a careful analysis of the NGIP documents in conjunction with an extensive literature search to identify research results applicable to NextGen to sort out the concepts, activities, and technologies, resulting in a proposed subset of these items; the process then focuses on the selected NGIP items to recommend modeling options to support simulation assessment of NextGen mid-term performance.

Optimal H 2 And H ∞ Fixed Order Dynamic Compensation Using Canonical Forms

This paper presents a technique for designing fixed order dynamic compensators in controller canonical form which are robust to both structured and unstructured uncertainty. The formulation uses an approach which combines an H2 and H∞ optimization process. Specificaly, a quadratic performance index is minimized subject to a constraint on the H∞, norm of the closed loop transfer function from disturbances to controlled outputs. This provides robustness to unstructured uncertainty. To provide robustness to structured uncertainty, an upper bound is computed for the worst case parameter variations, and it is then included in the derivation of the optimality conditions. For the specific case of no structured uncertainty, the results of this approach using the canonical form compensator are analytically related to the previously published results for a fixed or dynamic compensator. It is demonstrated that the use of the canonical form greatly simplifies the system of necessary conditions.

Models for Aircraft Surface Operations Environmental Analysis

Aircraft emissions at airports represent a significant environmental impact. Higher air quality standards have led to improvements in emissions over the past several decades, but future growth in air travel will make it more difficult to meet the standards. As part of current research into ways to improve airport surface operations, it was found that improved methods of estimating aircraft emissions on the surface were needed. The standard emissions analysis tool used in many studies is intended to capture the larger-scale trends and provides only a basic method of estimating emissions. New methods have been developed that take into account the dynamic behavior as aircraft maneuver around an airport and thus capture the smaller-scale variations. These models can provide more accurate estimates of emissions, at the expense of more detailed aircraft models.