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Reader is required to view these papers. 2005 AIAA Guidance, Navigation, and Control Conference, San Francisco, CA, August 15-18, 2005 A Rapid-Prototyping Environment for En Route Air Traffic Management Research P. K. Menon, G. M. Diaz, S. S. Vaddi and S. R. Grabbe An interactive software environment (CARAT#) that allows rapid prototyping of en route air traffic management algorithms is described. This software employs the NASA-FACET software as its computational engine, and allows the user to rapidly develop and evaluate en route air traffic management algorithms. Two versions of CARAT# have been developed. The first is built upon a commercial software platform, while the second version employs a freely available interactive, scriptable environment as its foundation. In addition to permitting direct access to the FACET capabilities, these interactive environments enable the users to readily build additional functionality into FACET and allow the rapid integration with several commercial software packages. The use of CARAT# software is illustrated through the formulation of a few research problems. Download Full Paper Multi-Stepping Solution to Linear Two Point Boundary Value Problems in Missile Integrated Control S. S. Vaddi, P. K. Menon, G. D. Sweriduk and E. J. Ohlmeyer A multi-stepping state transition matrix approach for solving a linear two-point boundary value problem is developed. The algorithm employs partitioned state transition matrix of the Hamiltonian system, and is computationally less expensive than backward integration of differential Riccatti equation. This fact makes it ideally suited for online implementation. The application of this technique is illustrated for a finite interval moving mass actuated missile guidance-autopilot for target interception. A combination of feedback linearization and the multi-stepping linear boundary value solution algorithm is employed in the example. Closed loop simulation results are given. Download Full Paper A Study of Near-Optimal Endurance-Maximizing Periodic Cruise Trajectories P. K. Menon, G. D. Sweriduk and A. H. Bowers A near-optimal 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 consumption 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 non-zero minimum throttle did show a modest improvement over the steady-state cruise performance, but only by 2.7%. Download Full Paper 23rd Digital Aviation Systems Conference (DASC), Salt Lake City, UT, October 24-28, 2004 Evaluation Plan for System-Wide Benefits of an Airport Surface-Operation Automation Concept V. H. L. Cheng The predicted growth in air travel requires capacity enhancement in the National Airspace System (NAS), and congestion at key airports has been recognized as one of the most prominent problem areas. With flights operating at limits dictated by operational requirements associated with current airport configurations, airport expansion plans involving addition of new runways and taxiways are in place to increase the airports’ capacities. However, the expansion projects necessarily increase the complexity of the airport configurations, which tends to penalize the efficiency of the system, partially offsetting the capacity-related benefits of the investments. The Surface Operation Automation Research (SOAR) concept has been proposed as a collaborative concept to provide automation for surface-traffic management (STM) and the flight deck to enhance the operational efficiency in complex airport environments, thus softening the unintended penalties associated with airport expansions. STM automation is based on the Ground-Operation Situation Awareness and Flow Efficiency (GOSAFE) concept previously reported to ease runway access conflicts, especially in situations where active-runway crossings constitute a significant taxi delay problem. To help achieve the potential GOSAFE benefits, the Flight-Deck Automation for Reliable Ground Operation (FARGO) concept has been proposed to provide the necessary flight-deck automation for enabling precision taxi control to comply with GO-SAFE advisories. Development and evaluation of the SOAR concept is being pursued in a 5-year program. A previous publication has documented an initial evaluation of the concept based on computer simulations of surface operations at a single hub airport. Expanding on this previous evaluation, this paper describes a NAS-wide evaluation effort to assess the system-wide benefits of the SOAR concept. Download Full Paper 2004 IEEE Intelligent Transportation Systems (ITSC), Washington, DC, October 3-5 Surface Operation Automation Research for Airport Tower and Flight Deck Automation V. H. L. Cheng Air traffic
growth has resulted in serious peaktraffic flight delays in our
National Airspace System, and congestion at key airports has been
recognized as one of the key factors contributing to the problem.
Airport expansion plans designed to increase the airports’
capacities cannot fully realize their potential benefits because
they tend to increase the complexity of the airport configurations,
thus reducing the efficiency of the system. The Surface Operation
Automation Research (SOAR) concept was proposed in a previous article 2004 AIAA Guidance, Navigation, and Control Conference, Providence, RI, August 16-19 Surface-Operation Benefits of a Collaborative Automation Concept V. H. L. Cheng, A. Yeh, G. M. Diaz, and D. C. Foyle The predicted
growth in air travel demands capacity enhancement in the National
Airspace System, and congestion at key airports has been recognized
as one of the most prominent future aviation problem areas. With
flights operating at limits dictated by operational requirements
associated with current airport configurations, airport expansion
plans involving addition of new runways and taxiways are being realized
to increase the airports’ capacities. However, the expansion
plans necessarily increase the complexity of the Computer-Aided Eulerian Air Traffic Flow Modeling and Predictive Control P. K. Menon , G. D. Sweriduk , T. Lam, G. M. Diaz, and K. D. Bilimoria 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 the U.S. airpsace. Download Full Paper Nonlinear Discrete-time Design Methods for Missile Flight Control Systems P. K. Menon , G. D. Sweriduk, S. S. Vaddi, and E. J. Ohlmeyer Discrete-time designs of flight control systems are required for implementation on missile-borne computers. While extensive literature is available on linear discrete-time control system design methods, nonlinear discrete-time control system design techniques have not been discussed to the same degree. This paper presents three nonlinear, discrete-time control system design methods. These are the discrete-time feedback linearization method, discrete-time state-dependent Riccatti equation method, and the discrete-time recursive backstepping technique. Nonlinear missile autopilot design for a conventional missile and an integrated guidance-control system design for a moving mass actuated missile are given as illustrative examples. Download Full Paper
2004 American Control Conference, Boston, MA, June 26–July 4 Estimation of Aperture Errors with Direct Interferometer-Output Feedback for Spacecraft Formation Control H.-L. Lu, V. H. L. Cheng, J. A. Leitner, R. G. Lyon, and K. G. Carpenter Long-baseline
space interferometers involving formation flying of multiple spacecraft
hold great promise as Journal of Guidance, Control, and Dynamics, Vol. 27, No. 1, pp. 118-126, January-February 2004 Integrated Guidance and Control of Moving Mass Actuated Kinetic Warheads P. K. Menon , G. D. Sweriduk, E. J. Ohlmeyer, and D. S. Malyevac 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. The moving-mass actuation technique offers significant advantages over conventional aerodynamic control surfaces and reaction control systems, since the actuators are contained entirely within the airframe geometric envelope and produce no plumes. The present research develops a 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 is employed for the design of nonlinear flight control systems. Interception of non-maneuvering and weaving targets in both endo-atmospheric and exo-atmospheric conditions is demonstrated. Download Full Paper Nonlinear Studies , Vol. 11, No. 2, pp. 173-198, 2004 Computer-Aided Synthesis of Nonlinear Missile Autopilots P. K. Menon , G. D. Sweriduk, and E. J. Ohlmeyer Powerful nonlinear approaches for missile autopilot design have recently emerged in the literature, which have the potential to deliver improved missile performance. However, the lack of computational methods has made it difficult for the practicing engineers to exploit these techniques in routine applications. Another factor that has slowed their application is that the missile models are generally available in the form of simulations, rather than as compact set of differential-algebraic equations. This makes it difficult to employ nonlinear control system design techniques requiring algebraic manipulations. This paper discusses five different approaches for computer-aided nonlinear control system design that ameliorate these difficulties. These design techniques are based on simulation models, enabling autopilot synthesis using missile models of arbitrary complexity. Airframe stabilization and command tracking of a nonlinear, longitudinal missile model is used to illustrative the design techniques. Download Full Paper 2003 AIAA Aircraft Technology, Integration, and Operations (ATIO) Technical Forum, Denver, CO, November 17–19 Flight Safety Analysis Tool for Space Vehicle Operations in the National Airspace V. H. L. Cheng, G. M. Diaz, and B. Sridhar The military, civilian and commercial demands on space access are expected to experience a continuing increase. The many potential applications have been greeted by a plethora of new launch vehicle concepts with promises to enable more launches with reduced cost and improved reliability. The expectation that some reusable launch vehicles can operate to and from regular runways suggests the possibility of having spaceports conveniently located over the continental US. However, the prospects of allocating reserved airspace to support the increasing frequency of launches will likely be unwelcome to the air transportation community. Furthermore, the relatively lower reliability of space transportation vehicles compared to that of air transportation vehicles means that their operational requirements will need to look beyond normal operations to account for their impact on the air traffic and ground populations. An analysis tool has been developed to facilitate the study of new launch vehicle concepts and new spaceport locations in terms of their impact on the air traffic and ground populations. The tool has potential applications in spaceport planning, launch licensing, and mission planning. It will allow air traffic control to anticipate the impact of space transportation operations on the air traffic, using data made available close to the launch or return time windows. It will also enable launch operators to monitor space launch and return operations with visualization of the real-time air traffic, and perform post-operation or post-accident analyses. Download Full Paper Evaluation Plan for an Airport Surface-Operation Automation Concept V. H. L. Cheng, A. Yeh, and D. C. Foyle The predicted growth in air travel demands capacity enhancement in the National Airspace System, and congestion at key airports has been recognized as one of the most prominent problem areas. With flights operating at limits dictated by operational requirements associated with current airport configurations, airport expansion plans involving addition of new runways and taxiways are being realized to increase the airports’ capacities. However, the expansion plans necessarily increase the complexity of the airport configurations, which tends to penalize the efficiency of the system, partially offsetting the capacity-related benefits of the investments. The Surface Operation Automation Research (SOAR) concept has been proposed as a collaborative concept to provide automation for surface-traffic management and the flight deck to enhance the operational efficiency in complex airport environments, thus reversing the penalties to fully realize the capacity benefits sought by the airport expansion plans. Development and evaluation of the SOAR concept is being pursued in a 5-year program, and this paper describes the experiments being designed for an initial evaluation during the second year of this program. Download Full Paper 2003 AIAA Guidance, Navigation, and Control Conference, Austin, TX, August 11–14 Investigation of Space Interferometer Control Using Imaging Sensor Output Feedback V. H. L. Cheng and J. A. Leitner Numerous space interferometry missions are planned for the next decade to verify different enabling technologies towards very-long-baseline interferometry to achieve high-resolution imaging and high-precision measurements. These objectives will require coordinated formations of spacecraft separately carrying optical elements comprising the interferometer. High-precision sensing and control of the spacecraft and the interferometer-component payloads are necessary to deliver sub-wavelength accuracy to achieve the scientific objectives. For these missions, the primary scientific product of interferometer measurements may be the only source of data available at the precision required to maintain the spacecraft and interferometer-component formation. A concept is studied for detecting the interferometer’s optical configuration errors based on information extracted from the interferometer sensor output. It enables precision control of the optical components, and, in cases of space interferometers requiring formation flight of spacecraft that comprise the elements of a distributed instrument, it enables the control of the formation-flying vehicles because independent navigation or ranging sensors cannot deliver the high-precision metrology over the entire required geometry. Since the concept can act on the quality of the interferometer output directly, it can detect errors outside the capability of traditional metrology instruments, and provide the means needed to augment the traditional instrumentation to enable enhanced performance. Specific analyses performed in this study include the application of signal-processing and image-processing techniques to solve the problems of interferometer aperture baseline control, interferometer pointing, and orientation of multiple interferometer aperture pairs. Download Full Paper Airport Surface Operation Collaborative Automation Concept V. H. L. Cheng Limitation in airport runway throughput naturally constrains traffic capacity. For this reason, the increasing demand on capacity ultimately will require airport expansion to increase the number of runways and associated taxiways. Often the airport expansion plans necessitate an increase in the complexity of surface traffic, leading to a decrease in surface traffic efficiency, which is reflected as an increase in taxi delays. Consequently any concept to increase airport traffic capacity needs to take into account efficiency issues such as taxi delays as well as safety and operator workload issues. This paper introduces a collaborative automation concept being developed under the Surface Operation Automation Research (SOAR) to address some of these issues in a complex airport environment. The concept is enabled by advanced technologies envisioned for the 2020 time frame. It involves surface traffic management (STM) automation to aid tower operation, and flight-deck automation to help execute clearances generated by the STM automation for efficient surface operation. The functions of and integrated operation between these automation components are described, together with an assessment of enabling technologies in communication, navigation, and surveillance. Plans for evaluating the collaborative concept prior to full-scale technology development are discussed. Download Full Paper Optimal Fixed-Interval Integrated Guidance-Control Laws for Hit-to-Kill Missiles P. K. Menon, G. D. Sweriduk, and E. J. Ohlmeyer Due to their
potential for reducing the weapon size and efficiency, design methods
for realizing hit-to-kill capabilities in missile systems are of
significant research interest in the missile flight control community.
As defined in this paper, hit-to-kill capability requires the missile
to consistently achieve point-mass miss distances less than half
the minimum dimension of the target. It has been noted in the literature
that the chief contributors to the miss distance in homing missiles
are the seeker errors, autopilot lag, target maneuvers, and target
state estimation lag. Guidance laws for ameliorating the effects
of each of these miss distance components have been discussed in
several recent publications. Air Traffic Flow Modeling, Analysis, and Control P. K. Menon, G. D. Sweriduk, and K. D. Bilimoria Development of a methodology for mathematical modeling and analysis of air traffic flow is presented. The modeling approach describes the air traffic environment in terms of traffic counts in user-defined elements of the airspace system, and traffic flows between these elements. The resulting Eulerian model of air traffic allows dynamic analysis and flow-control system design using well-established control theoretic approaches. The primary advantage of the Eulerian approach is that the dimension of the air traffic flow model depends only on the number of defined elements in the traffic network, and remains invariant with respect to the number of aircraft in the airspace system. Analytical development, computational implementation, and traffic flow modeling and control of a regional airspace are discussed in the paper. Download Full Paper 21st IEEE/AIAA Digital Avionics Systems Conference, Irvine, CA, October 29–31, 2002 Computer Simulation and Analysis Tool for Air and Space Traffic Interaction Research V. H. L. Cheng, P. K. Menon, B. Sridhar, and C. H. Draper Driven by anticipated increase in satellite deployments and corresponding increase on space-launch demand, numerous domestic and international government programs as well as several “start-up” private ventures have been formed to develop launch vehicles that will provide less expensive alternatives to the current fleet, including numerous reusable launch vehicle concepts. The different launch-vehicle concepts are expected to have different operational characteristics, and thus different impact and requirements on the National Airspace System (NAS). This paper describes a set of computer analysis capabilities being developed for the study of air traffic management issues related to the space operations. Download Full Paper Collaborative Automation Systems for Enhancing Airport Surface Traffic Efficiency and Safety V. H. L. Cheng To realize the operational throughput offered by the available runways, operational procedures favoring landing and takeoff operations over other runway occupancies such as crossing by the taxiing traffic have to be adopted. Consequently, the increase in surface traffic complexity leads to an efficiency penalty in the form of taxi delay. This problem is exacerbated by the increase in traffic density enabled by the improved landing/departure rates. This paper considers a concept for improving the surface operations at major airports through the use of automation to manage the complex traffic. The concept includes advanced surface-traffic-control automation and flight-deck automation, and it builds on advanced Communication, Navigation, and Surveillance technologies to achieve a seamless integration of these two major components. Download Full Paper 2002 AIAA Guidance, Navigation, and Control Conference, Monterey, CA, August 5–8 Automation Tools for Enhancing Ground-Operation Situation Awareness and Flow Efficiency V. H. L. Cheng and D. C. Foyle This paper considers the surface-traffic problem at major airports and envisions a collaborative traffic and aircraft control environment where a surface traffic automation system will help coordinate surface traffic movements. A previous study has established the performance potential of advanced guidance and control of a transport aircraft to deliver high-precision taxi capability. This paper describes the development of a surface traffic automation system, known as Ground-Operation Situation Awareness and Flow Efficiency (GO-SAFE). The GO-SAFE system is designed to work with advanced surveillance and communications technologies, and anticipated air traffic automation systems under development. It includes tools to help the ground controller with predicted traffic information, functionality to manipulate taxi routes, and advanced capabilities to schedule runway usage to accommodate landing, takeoff, and crossing traffic. Download Full Paper 2002 American Control Conference, Anchorage, AK, May 8 – 10 Real-Time Computational Methods for SDRE Nonlinear Control of Missiles P. K. Menon, T. Lam, L. S. Crawford, V. H. L. Cheng The state dependent
Riccati equation (SDRE) technique is a recently developed methodology
for designing control laws and estimation algorithms for missile
flight control. Although its potential is well recognized by control
theory experts, the industry acceptance of the technique has been
slow. The main reasons for this are: a) unlike linear control technology,
the SDRE approach requires advanced numerical methods for its implementation,
which are not currently available off-the-shelf, b) the perception
that this technique may not be computationally feasible for real-time
implementation on flight control processors. IEEE Transactions on Intelligent Transportation Systems, Vol. 2, No. 2, pp. 39–54, June 2001 Study of Aircraft Taxi Performance for Enhancing Airport Surface Traffic Control V. H. L. Cheng, V. Sharma, and D. C. Foyle This paper considers the surface-traffic problem at major airports and envisions a collaborative traffic and aircraft control environment where a surface traffic automation system will help coordinate surface traffic movements. Specifically, this paper studies the performance potential of high-precision taxi towards the realization of such an environment. A state-of-the-art nonlinear control system based on feedback linearization is designed for a detailed B-737 aircraft taxi model. The simulation model with the nonlinear control system is evaluated extensively in a scenario representing the demanding situation of an arrival aircraft crossing an adjacent active runway immediately following its own landing. The evaluation establishes the potential of an automated system to achieve high-precision taxi control, including the ability to comply with taxi clearances with tight time margins. Download Full Paper IFAC - Control Engineering Practice, Vol. 9, pp. 1095-1106 Integrated Design of Agile Missile Guidance and Autopilot Systems P. K. Menon and E. J. Ohlmeyer Recent threat
assessments by the US Navy have indicated the need for improving
the accuracy of defensive missiles. This objective can only be achieved
by enhancing the performance of the missile subsystems and by finding
methods to exploit the synergism existing between subsystems. As
a first step towards the development of integrated design methodologies,
this paper develops a technique for integrated design of missile
guidance and autopilot systems. Traditional approach for the design
of guidance and autopilot systems has been to design these subsystems
separately and then to integrate them together before verifying
their performance. Such an approach does not exploit any beneficial
relationships between these and other subsystems. The application
of the feedback linearization technique for integrated guidance-autopilot
system design is discussed. Numerical results using a six degree-of-freedom
missile simulation are given. 2000 AIAA Missile Sciences Conference, Montery, CA, November 7–9 Integrated Guidance-Control Systems for Fixed-Aim Warhead Missiles P. K. Menon and E. J. Ohlmeyer Integrated guidance-control
systems have the potential to improve missile system performance
by taking advantage of the synergism existing between subsystems.
These systems allow the designer to impose unusual performance requirements
on the missile. Such requirements may arise out of the new sensor
and warhead technologies that may require complex maneuvers at target
interception. 8th AIAA/NASA/USAF/ISSMO Symposium on Multidisciplinary Analysis and Optimization, Long Beach, CA, September 6–8, 2000 Near-Optimal Antenna Placement Using Genetic Search L. S. Crawford, V. H. L. Cheng, R. Burns, and S. Liu The optimal
placement of ground stations and antennas in the Air Force Satellite
Control Network (AFSCN) to support the operation of a large set
of satellites is a very difficult problem involving many complex,
interacting constraints and requirements. This paper explores the
application of genetic search techniques to antenna-placement optimization.
The performance index used in the genetic search optimization was
based on a candidate configuration’s cost. Requirements on
the number of satellite contacts that could be scheduled with the
configuration were imposed as constraints. 1999 IEEE International Conference on Control Applications, Hawai'i, HA, August 22-27 Air Traffic Control Using Genetic Search Techniques V. H. L. Cheng, L. S. Crawford, and P. K. Menon Genetic search techniques constitute an optimization methodology effective for solving discontinuous, non-convex, nonlinear, or non-analytic problems. This paper explores the application of such techniques to a non-analytic event-related air traffic control problem, that of runway assignment, sequencing, and scheduling of arrival flights at an airport with multiple runways. Several genetic search formulations are developed and evaluated with a representative arrival traffic scenario. The results exemplify the importance of the selection of the chromosomal representation for a genetic-search problem. Download Full Paper 1999 AIAA Guidance, Navigation, and Control Conference, Portland, OR, August 9-11 Synthesis of Flight Vehicle Guidance and Control Laws Using Genetic Search Methods L. S. Crawford, V. H. L. Cheng, and P. K. Menon Guidance and control problems in which the system dynamics or the performance measures are discontinuous, non-smooth, or non-convex are difficult to attack with conventional methods. Genetic search techniques can be extremely useful for these types of problems, as genetic methods are not gradient-based and can operate regardless of the complexity of the problem dynamics or performance specifications. In this paper, genetic search methodologies are applied to solving a set of aerospace guidance and control problems. These problems include homing missile guidance, spacecraft reorientation, and advanced aircraft control and guidance logic. The examples presented here demonstrate the advantages of genetic search methods in synthesizing nonlinear guidance and control laws for systems that may be difficult or intractable with conventional approaches. Download Full Paper Software Tools for Nonlinear Missile Autopilot Design P. K. Menon, V. R. Iragavarapu, E. J. Ohlmeyer A computer-aided design software package for nonlinear control synthesis is discussed. The software incorporates five different modern nonlinear control methods. The versatility of the software lies in its ability to develop nonlinear controllers using a simulation model. As a result, models of arbitrary complexity can be used in the control law development. The use of the design software is illustrated through the design of nonlinear regulators for a longitudinal missile model. Download Full Paper Design Of a Pilot-Activated Recovery System Using Genetic Search Methods G. D. Sweriduk, P. K. Menon, M. L. Steinberg Control design tasks often require the use of trial-and-error search methods to obtain a satisfactory solution. Depending upon the nature and the number of "tuning" parameters or functions, the search process can be very discontinuous and nonconvex. The genetic search methods are a recently developed family of techniques for optimization which offer certain advantages over other techniques. These include greater freedom in defining cost functions and constraints, and the ability to automate the design process. Most notably, though, is the ability to construct new control laws and the potential to generate non-intuitive solutions as well. This paper demonstrates the application of genetic search methods to design a Pilot-Activated Recovery System (PARS) for a modern fighter aircraft. The PARS is a guidance law that transfers the aircraft from any initial attitude to a wings-level, nose-up, recovered flight condition. This system is useful in cases of pilot disorientation. A 6 degree-of-freedom nonlinear model of a modern, high-performance aircraft is used for design. The genetic search seeks to produce nonlinear feedback functions to meet the specified goals and constraints. This intricate problem highlights some of the advantages of this emerging search technique. Download Full Paper Low-Thrust Orbit Transfer Optimization Using Genetic Search L. D. Dewell and P.K. Menon Most techniques for solving dynamic optimization problems involve a series of gradient computations and one-dimensional searches at some point in the optimization process. A large class of problems, however, does not possess the necessary smoothness properties that such algorithms require for good convergence. Even when smoothness conditions are met, poor initial guesses at the solution often result in convergence to local minima or even a lack of convergence altogether. For such cases, genetic search techniques can be used to obtain a solution. In this paper, trajectory optimization using genetic search methods is illustrated by solving a complex, nonlinear problem involving low-thrust orbit transfer. Download Full Paper A Study on Aircraft Taxi Performance Using Nonlinear Feedback Control V. H. L. Cheng, V. Sharma, D. C. Foyle Whenever traffic density becomes so critically high that it begins to jeopardize efficiency and safety, the answer lies in the ability to improve traffic coordination and movement precision. This study considers the surface-traffic problem at major airports, and establishes the possibility of high-precision taxi operations by applying state-of-the-art automatic control technologies. Due to the high-speed environment, high-precision taxi is most difficult on or across the runway, where such ability is also potentially most beneficial. In this study, a nonlinear guidance and control system is synthesized and its potential performance in high-precision taxi control is verified, including the ability to taxi continuously immediately after landing to cross an adjacent runway with the tightest of time margin. Download Full Paper 1999 Mediterranean Control Conference, Haifa, Israel, June 28-30 Integrated Design of Agile Missile Guidance and Autopilot Systems P. K. Menon and E. J. Ohlmeyer Recent threat
assessments by the US Navy have indicated the need for improving
the accuracy of defensive missiles. This objective can only be achieved
by enhancing the performance of the missile subsystems and by finding
methods to exploit the synergism existing between subsystems. As
a first step towards the development of integrated design methodologies,
this paper develops a technique for integrated design of missile
guidance and autopilot systems. Traditional approach for the design
of missile guidance and autopilot systems has been to design these
subsystems separately and then to integrate them together before
verifying their performance. Such an approach does not exploit any
beneficial relationships between these and other subsystems. 1999 American Control Conference, San Diego, CA, June 2-4 Adaptive Target State Estimation Using Neural Networks P. K. Menon, V. Sharma Development of an adaptive target state estimation algorithm for use with advanced missile guidance laws is presented. The target state estimator employs a linear neural network as the decision-making element in a nine-state dynamic model of the target. A Kalman filtering algorithm is used to estimate the neural network weights and the target states. The estimator performance is evaluated in a point-mass nonlinear simulation of missile-target engagement for several different engagement scenarios. This simulation incorporates error models of the seeker and the on-board inertial navigation system. Comparison of the neural network target state estimator performance with a conventional target state estimator reveals that the adaptive estimator provides more accurate estimates of the target states with minimal lag. Download Unavailable 1998 AIAA Guidance, Navigation and Control Conference, Boston, MA, August 10-12 Blended Homing Guidance Law Using Fuzzy Logic P. K. Menon and V. R. Iragavarapu The application of fuzzy logic for the development of guidance laws for homing missiles is presented. Fuzzy logic approximation of the well known proportional navigation guidance law is discussed, followed by the development of a blended guidance law using fuzzy logic. The objective of the latter guidance law is to combine desirable features of three homing guidance laws to enhance the interception of targets performing uncertain maneuvers. Fuzzy logic guidance law development employs triangular, trapezoidal and sigmoidal membership functions. Mamdani-style inference is employed in the fuzzy inference system. Simulation results using point-mass missile model and a spiraling, high-speed ballistic target model are given. Download Full Paper Adaptive Techniques for Multiple Actuator Blending P. K. Menon and V. R. Iragavarapu Advanced missiles employ multiple actuators to enhance maneuverability and to improve the intercept probability against highly maneuverable targets. Actuators employed in such missiles include aerodynamic control surfaces and reaction jets. While the usage of aerodynamic surfaces are not generally constrained, reaction jet usage has to be minimized due to the limited amount of fuel available on-board. A blending logic is employed to optimally allocate the actuators in response to commands from the autopilot. This paper discusses the development of a fuel conservative actuator blending logic that provides relatively invariant actuator performance over widely varying flight conditions. The invariant performance is obtained using the model reference adaptive control technique. Multiple adaptation strategies are employed to ensure rapid convergence and stable behavior. The performance of the model reference adaptive actuator blending strategy is illustrated using a realistic missile model. Download Full Paper Robust Command Augmentation System Design Using Genetic Search Methods G. D. Sweriduk and P. K. Menon This paper describes the use of a genetic search method in the design of a command augmentation system for a high-performance aircraft. A genetic algorithm is used in the design of HÆ controllers for the longitudinal and lateral-directional channels by selecting the weighting functions. The integral of absolute value of error between the actual response and that of an ideal model is used as the fitness criterion, along with additional terms to penalize for cross-coupling, non-minimum phase behavior, and the closed-loop infinity-norm bound. Starting from an initial population of weighting functions, the algorithm generates new functions with the goal of improving the fitness. These controllers are then evaluated in a 6 degree-of-freedom nonlinear model of the aircraft. Download Full Paper 1997 AIAA Guidance, Navigation and Control Conference, New Orleans, LA, August 11-13 Optimal Strategies for Free Flight Air Traffic Conflict Resolution P. K. Menon, G. D. Sweriduk and B. Sridhar Recent advances in navigation and data communication technologies make it feasible for individual aircraft to plan and fly their trajectories in the presence of other aircraft in the airspace. This way, individual aircraft can take advantage of the atmospheric and traffic conditions to optimally plan their paths. This capability is termed as the free flight concept. While the free flight concept provides new degrees of freedom to the aircraft operators, it also brings-in complexities not present in the current air traffic control system. In the free flight concept, each aircraft has the responsibility for navigating around other aircraft in the airspace. While this is not a difficult task under low speed, low traffic density conditions, the complexities of dealing with potential conflict with multiple aircraft can significantly increase the pilot's work load. This paper presents the development of a conflict resolution algorithm based on the quasi-linearization method to enable the practical implementation of the free flight concept. The algorithm development uses nonlinear point-mass aircraft models, and incorporates realistic operational constraints on individual aircraft. The analytical framework can also incorporate information about ambient atmospheric conditions. Realistic conflict resolution scenarios are illustrated. Due to their speed of execution, these conflict resolution algorithms are suitable for implementation on-board aircraft. Download Full Paper Nonlinear Missile Autopilot Design Using Time-Scale Separation P. K. Menon, V. R. Iragavarapu and E. J. Ohlmeyer Time-Scale separation helps improve the robustness of feedback linearized autopilots by simplifying the feedback linearization maps, and by permitting the design of low-order controllers. This paper presents the development of three distinct time-scale separation schemes for the design of feedback linearized missile autopilots. A six degrees-of-freedom missile model is used in this work. The performance of these autopilots are compared with the design that does not use time-scale separation. Simulation results illustrating controller tracking performance and robustness are presented. Download Unavailable 1996 AIAA Guidance, Navigation and Control Conference, San Diego, CA, August 11-13 Design of Nonlinear Autopilots for High Angle of Attack Missiles P. K. Menon and M. Yousefpor Two nonlinear autopilot design approaches for a tail-controlled high angle of attack air-to-air missile are described. The research employs a highly nonlinear, time varying pitch plane rigid-body dynamical model of a short range missile. Feedback linearization technique together with linear control theory are then used for autopilot design. In order to manage the difficulties associated with "zerodynamics" that arise in tail controlled missiles, two distinct approaches for approximate feedback linearization are advanced. The first approach imposes a time-scale structure in the closed-loop dynamics, while the second technique redefines the output. Performance of these autopilots are illustrated in a nonlinear simulation. Download Full Paper Differential Game Based Guidance Law for High Angle of Attack Missiles P. K. Menon and G.B. Chatterji A nonlinear differential game theoretic intercept guidance law for short range missiles is derived. Differential geometric transformations are used to convert the nonlinear missile and the target models into a convenient form for the formulation and solution of the guidance problem. Guidance law is then derived using the necessary conditions for optimality. Due to the inclusion of all the significant nonlinearities in the formulation, the guidance law is useful in advanced missiles executing large angle of attack maneuvers. The guidance law performance is illustrated in air-to-surface and air-to-air intercept missions. Download Full Paper Enhancing Aircraft Performance Through Flight/Propulsion System Integration P. K. Menon, V. R. Iragavarapu and S. Garg Aircraft performance enhancement by integrating the propulsion control system with the primary flight control system is demonstrated through two nonlinear flight control design examples. In the first example, high performance aircraft turning performance improvement using engine thrust modulation is demonstrated. In the second example, the flight propulsion system integration is used to achieve precise flight time control for a transport aircraft. Both control law designs are based on feedback linearization, and exploit the aircraft dynamic models. Realistic aircraft models are used to illustrate the responses of the nonlinear integrated flight/propulsion control systems. Download Full Paper 52nd AHS Forum, Washington, D.C., June 4-6, 1996 Real-Time Estimation of Rotorcraft Limit Envelopes Using Neural Networks P. K. Menon, V. R. Iragavarapu and M. S. Whalley Helicopter operation is constrained by complex limit envelopes that are difficult to predict and poorly enunciated to the pilot. The ability to sense and automatically avoid these limits can protect the rotorcraft from loss of control, avoid catastrophic failure, reduce the number of minor exceedances that degrade airframe fatigue life, and permit the pilot to safely fly the aircraft closer to the edge of the envelope. The development and operation of a neural network-based rotorcraft limit detection system that generates rotorcraft limit avoidance data using on-board measurements is discussed. The system combines manufacturer's envelope limit data together with adaptively determined envelope limits on-board the aircraft. Both time-varying and time-invariant limits are included in the neural network. The operation of the limit detection neural network is demonstrated using data obtained from six-degree-of-freedom manned rotorcraft simulations. Download Unavailable |