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In recent years, there has been an increased emphasis on undergraduate research. High tech companies need research to keep them competitive. This paper addresses the issue of getting engineering and computer science students interested in focused engineering and computer science areas so they are excited about these topics and want to learn more by doing research in that area. Our method is to encourage the student to research and write an interest paper as a first step to writing a proposal to seek and do organized research. In order to evaluate this approach, a survey was completed by 57 students in an Academic Success and Professional Development class who were assigned the writing of an interest paper in engineering or computer science. Results show that the assignment was successful for some students in leading them to an area of research in which they were interested and in other cases learning that they were not that interested in a particular area. Other students found a second interest. In this assignment, some students used an engineering data base for the first time.

In order to have more students in engineering and computer science, we need more students interested in these fields. Many community college (CC) students believe that engineering is boring and has little to do with their lives, but also admit that they know very little about engineering. Our research question is: How can we best get the attention of CC students in order for them to get engineering and computer science on their radar screen to consider as a career? In particular, we are asking if a different approach is needed for underrepresented minority students than majority students. A survey was given to 72 students (21 minority) students at one non-metropolitan CC and 159 (112 minority) students at another. In this paper, we will compare the beliefs about engineering and computer science by ethnicity within each college and across the two CCs. Results show that a higher percentage of non-minority students at the first school are interested in engineering and computer science as a career (63%) than minority students (52%) and at the second school, a higher percentage of minority students (45%) than non-minority students (35%) are interested in engineering or computer science, even if about 20% of each group admit that they really don't understand what engineering is all about. The minority students appear to be more interested in working with robotics and are more likely to believe that engineering and computer science have nothing to do with their life than do non-minority students.

Arizona and the United States need more engineers. It is well known that very few college freshmen choose engineering as a major. In addition, studies show that roughly 40% of students planning to study engineering and science change majors or fail to get their degrees. Students aspiring to be an engineer must take several years of mathematics courses. Mathematics is not popular. In a recent Noel-Levitz study, 45% of today's freshmen agreed with the statement, "Math has always been a challenge for me." A discouraging fact is that many high school and community college students know very little about engineering and thus do not even have it on their radar as a possible career. This team of authors have been working with precollege and community college students for over 10 years trying to increase the number of engineers. They have made many visits to community colleges and to high schools to talk about engineering. At the same time they had done research on these students to better understand them and to help determine the best practices to interest more students in engineering. This paper gives the results of surveys that have been given to high school and to community college students to try to determine their largest areas of ignorance or misunderstanding regarding engineering and computer science. This information can then inform how best to use a limited amount of time with undecided students to break down these barriers.

In this paper we consider the design and control of an airbreathing hypersonic vehicle. Such vehicles are characterized by non-minimum phase characteristics, instability, actuator saturation constraints, and lightly damped flexible modes. While traditional vehicle design has followed an iterative sequential procedure (with the controller design following an aero-centric vehicle design phase), an integrated vehicle-control design process (based on bilinear matrix inequalities) is considered in this paper. We consider several example problems to illustrate the advantages of such an approach.

A Windows/C/C++ personal computer- based program is developed and used to evaluate the performance of missile guidance and control systems. The program simulates a high-performance missile in pursuit of an evading target. The simulation includes realistic missile and actuator dynamics, an autopilot, several missile guidance laws, a seeker/ navigation system model, various target models, and several integration methods. Missile-target intercepts are simulated and graphically displayed using the C/ C++ programming language. This represents a considerable improvement over previous research due to the object- oriented structure, speed, maintainability, and ease of debugging that C/C+ + offers. For modularity, the program is organized into three blocks: program-user interface, simulation, and graphics. Various simulations are presented to demonstrate the utility of the program in the evaluation of missile guidance and control systems.

Two robust controller designs are presented for a twin lift helicopter system (TLHS). The TLHS configuration consists of two UH-60A Sikorsky Blackhawk helicopters jointly lifting a heavy payload. The first design presented considers the case in which the tethers connecting each helicopter to the load are equal in length, and the second considers the case in which the tether lengths are unequal. Both designs are based on a seven degree of freedom model linearized about hover. The primary objective of each controller is to minimize the control action and pitching motion required to stabilize the helicopters as they perform elementary manuevers. Initial controllers developed by solving a mixed sensitivity H ∞ problem are analyzed for robustness to model uncertainty using the structured singular value μ and new controllers are developed which are more robust with respect to the uncertainty.

In this paper, three methods are presented to enhance the performance of an unstable missile system in the presence of multiple saturating actuators. Each method involves the design of a saturation detection system, which modifies a nominal autopilot via online optimization and maintains, to the extent possible, the multivariable properties of the nominal design. To prevent saturation due to exogenous signals, disturbances and noises, in particular, an error governor is proposed. This system processes the error signals within the feedback loop and the state of the compensator, so that appropriately co-ordinated control surface deflections may be generated. Traditionally, such a system has been applied only to stable plants. In this paper, it is shown how to design such a system for unstable plants. To prevent saturation due to reference (acceleration) commands from the guidance system, a reference governor is proposed. Such a system has traditionally required access to the entire state of the plant as wel...

In this paper we consider limits of achievable performance for a class of scramjet-powered hypersonic aircraft. A simple 3-DOF model is used to illustrate the main ideas. The vehicle is characterized by unstable and non-minimum phase dynamics. The limitations introduced by the right-half plane zero and actuator saturation on achievable trajectories has been examined. In addition, we examine several vehicle configurations and consider fundamental limitations for the plant and closed loop performance. An optimization methodology that explicitly incorporates performance specifications into the design of vehicle is explored. The advantages of such an approach is illustrated with examples.

This paper examines the issues involved in controlling an air-breathing hypersonic vehicle (characterized by their unstable, non-minimum phase dynamics) in the presence of significant modeling uncertainty and nonlinearities (control saturations). Modeling of the vehicle exhaust (plume) is complicated, often requiring computational fluid dynamic (CFD) simulations to capture all relevant effects. The focus of this paper is on obtaining a control law that maintains the vehicle trajectory within an acceptable tube while enforcing control constraints in the presence of modeling uncertainty. A robust domain of attraction based approach is used to generate/validate a feasible tube. The computational aspects of such an approach is examined, and the benefits of a decentralized control technique is considered. This approach is compared with other techniques such as linear matrix inequalities based controller design. These approaches are applied to a command following scenario in order to illustrate the performance of the proposed approach.

In this paper, two methods are presented to enhance the performance of unstable missile system in the presence of saturating actuators. Each method involves the design of a saturation detection system which modifies a nominal autopilot via on-line optimization and maintains, to the extent possible, the multivariable properties of the nominal design. Each method is applied to the problem of controlling an unstable bank-to-turn (BTT) missile.

This paper examines control-relevant modeling issues for a class of scramjet-powered hypersonic vehicles. A simple nonlinear 3DOF model is used to illustrate the main ideas. Two different plume modeling methodologies from previous literature are compared to a newly developed methodology. The impact of the modeling method on vehicle design has been examined. Nominal control design robustness issues are also addressed.

Within this paper, control-relevant vehicle design concepts are examined using a widely used 3 DOF (plus flexibility) nonlinear model for the longitudinal dynamics of a generic carrot-shaped scramjet powered hypersonic vehicle. The impact of elevator size and placement on control-relevant static properties (e.g. level-flight trimmable region, trim controls, Angle of Attack (AOA), thrust margin) and dynamic properties (e.g. instability and right half plane zero associated with flight path angle) are examined. Elevator usage has been examine for a class of typical hypersonic trajectories.

In this paper, an overview is provided of control efforts implemented using the scramjetpowered hypersonic vehicle model developed by Bolender, Doman, et.al. (2005-2009). The nonlinear model is characterized by unstable non-minimum phase dynamics with aeroelastic-propulsion coupling and nonlinear propulsion constraints. The viability of simple inner-outer loop single-input single-output (SISO) control structures is examined and quantified. Reference command and control amplitude and bandwidth tradeoffs are addressed. A simple (non-scheduled ) inner-outer loop control law is shown to yield excellent tracking of a constant (q = 2076 psf) dynamic pressure guidance command profile from Mach 5.7 to Mach 12. Robustness, gain scheduling as well as multivariable control issues are also addressed.

Effects of hot band annealing on the final microstructure and magnetic properties of cold rolled and annealed non-oriented grain Si-Al electrical steel strips are investigated. Microstructures are characterized using optical and scanning electron microscopy and magnetic properties are determined using a vibrating sample magnetometer. It is shown that annealing of hot rolled bands at temperatures between 800 and 850 °C causes rapid decarburization and development of a microstructure consisting of large columnar ferrite grains free of secondary particles. This microstructure leads, after cold rolling and a fast annealing treatment, to large grain microstructures similar to those observed in production scale, fully processed strips. It is observed that the final grain size increases with the final annealing temperature, leading to a significant improvement of the magnetic properties. Therefore, hot band annealing technology can be an attractive alternative processing route for the manufacture of non-oriented grain low carbon Si-Al processed electrical steel strips.

Scramjet powered hypersonic vehicles represent the next critical step toward achieving NASA's vision for Highly Reliable Reusable Launch Systems (HRRLS), affordable space access, planetary re-entry systems, and global reach vehicles. The design of such vehicles is a very interdisciplinary and highly complex problem. As such, the development of varying fidelity mathematical models for assessing overall stability and performance during the design process is very important. In particular, developing “low-order” models with “sufficient fidelity” to capture control-centric phenomena becomes vital in early stages of vehicle design. Historically, the early stage vehicle design process never incorporated control related considerations. The design obtained by such practice is not optimal and can often lead to poor design from a stability and performance view point. This paper presents control-relevant modeling efforts which will facilitate quick iterative control analysis and design during early stages of vehicle design. The paper is intended to be of an introductory nature and presents the high level modeling framework and associated challenges. An example linear 6 DOF model with some representative analysis is also given to demonstrate the applicability of the tool suite.

In this paper, we provide an overview of scramjet-powered hypersonic vehicle modeling and control challenges. Such vehicles are characterized by unstable non-minimum phase dynamics with significant coupling and low thrust or FER (normalized fuel equivalency ratio) margins. Recent trends in hypersonic vehicle research is summarized. To illustrate control system design issues and tradeoffs, a generic nonlinear 3DOF longitudinal dynamics model capturing aero-elastic-propulsive interactions for wedge-shaped vehicle is used. The model is analyzed over a broad range of hypersonic flight conditions (i.e. operating points). The paper highlights how vehicle level-flight static (trim) and dynamic properties change over the trimmable air-breathing corridor (∼ Mach 4.75-12.6, 70-115 kft). Particular attention is paid to thermal choking constraints imposed on control system design as a direct consequence of having a finite FER margin. The dependence of FER margin on altitude, Mach, and the bow flow turning angle is discussed. The latter depends on Mach, altitude, angle-of-attack (AOA), and forebody flexing. It is (briefly) discussed how FER margin can be estimated on the basis of Mach, altitude, and AOA if a flexing upper bound is assumed. The implication of this state-dependent nonlinear FER margin constraint as well as that of the right half plane (RHP) zero, associated with the elevator-flight path angle (FPA) map, on control system bandwidth (BW) and FPA tracking are discussed. It is argued that while the non-minimum phase zero limits the achievable closed loop FPA BW, FER coupling into FPA can be used to address this. This, however, is limited by FER margin limits and may impose constraints on the size of the FPA (and velocity) commands that can be followed. This is particularly important because the vehicle is inherently unstable which implies a closed loop system (with a finite downward gain margin) that can become destabilized if driven sufficiently deep into control saturation. A consequence of this is that designers must take note of the fact that FPA commands which are sufficiently large and/or rapid may be impossible to follow with the desired level of fidelity. This is quantified within the paper. Speed command following issues are also discussed.

*Morphing research projects will revolutionize the costs of building and operating aircraft. These technologies will enable aircraft to be more effi cient and operate under a wide range of varying flight conditions. Morphing technologies will be used to improve aircraft performance, expand its flight envelope, replace conventional control surfaces, reduce drag to improve range and reduce vibration/flu tter. There might never be a single solution for a morphing aircraft. The suitability of a type of morphing technology that is integrated into an aircraft will be dependent on size, range and flight performance envelope. The largest economical motivator for morphing aircraft will be the economies of scale of having a fleet of single type of morphing aircraft capable of fulfilling a variety of mission objectives and functions under many flight conditions , as opposed to a fleet of several types of aircraft , each tailored for specific missions , and their corresponding maintenance and support requirements. It is the objective of this survey paper to organize and summarize the many varying projects, concepts , and technologies of morphing aircraft. This surve y is not all inclusive. The two general approaches to morphing aircraft technologies are a Materials and Structural Approach , and a MultiDisciplinary Optimization and Systems Approach.

In many applications, it is essential to limit control signals. This paper presents methods that process accessible system signals (e.g., plant and compensator states, reference commands) to limit control signals. In contrast to "classical techniques" which limit variables by unnecessarily reducing control system bandwidth, the proposed methods limit variables in a nonconservative manner, reducing bandwidth only when necessary. A fundamental contribution of this work is that the methods presented are applicable to linear parameter varying (LPV) and quasi-LPV plants and controllers. The methods presented rely on appropriately "scaling back" key signals. The methods are conservative in that they are applicable to "slowly varying" LPV systems. Although the methods require access to all internal closed loop system state variables, one could use an appropriately designed LPV state estimator, if necessary. The Error Governer (EG) methods are applied to an LPV missile autopilot example.

This paper describes the synthesis of a dynamic compensator for a flexible space telescope described by a 280/sup th/ order finite-element NASTRAN-based model. The control objective is to attenuate the induced LOS jitter by a factor of 40 dB over the open loop value. A combination of low authority control (LAC) followed by high authority control (HAC/sub /spl infin//) which utilizes the H/sup /spl infin// optimal control methodology make up the hierarchical control system developed in this paper. The final design is shown to offer the required performance and robustness. The LAC loop is made up of two loops which provide broadband modal damping, modal spillover robustness, and actuator mode stabilization; all of which help in the design of the HAC/sub /spl infin//. The HAC/sub /spl infin// loop controller order is reduced from 130-states to 60-states by applying frequency-weighted balanced truncation techniques. The resulting hierarchical HAC/sub /spl infin///LAC controller is robustly stable against /spl plusmn/10% variation in actuator and sensor modeling.

In this paper, a method is presented for enhancing the performance of a stable EMRAAT bank-to-turn (BTT) missile in the presence of multiple saturating actuators. The method involves the design of a saturation detection system, called an error governor which maintains, to the extent possible, the multivariable properties of the original autopilot design. The system prevents saturation, ensures finite-gain L/sup /spl infin// stability, and maintains, to the extent possible, the directionality properties of the original autopilot.

In this paper, a method is presented for enhancing the performance of an unstable missile system in the presence of multiple saturating actuators. The method involves the design of it saturation detection system which modifies a nominal autopilot via online optimization and maintains, to the extent possible, the multivariable properties of the nominal design. The method relies on missile state estimates.

Two H/sup infinity / controller designs are presented for a twin lift helicopter system (TLHS). The TLHS configuration consists of two US-60A Sikorsky Blackhawk helicopters jointly lifting a heavy payload. The first design presented considers the case in which the tethers connecting each helicopter to the load are equal in length, and the second considers the case in which the lengths are unequal. Both designs are based on a seven-degree-of-freedom model linearized about hover. The primary objective of each controller is to minimize the control action and pitching motion required to stabilize the helicopters as they perform elementary maneuvers. A simulation of a typical TLHS command scenario is used to evaluate the stability robustness characteristics of the resulting two feedback systems with respect to structured parametric uncertainty. >

This educational research endeavor describes the development of a Windows/C++ PC environment designed to visualize and evaluate the performance of a Twin Lift Helicopter System (TWS) under automatic control. The TLHS consists of two Sikorsky UH-60A Blackhawk helicopters, jointly lifting a heavy payload. The program-user interface permits users to change critical model and control law parameters in real-time. TLHS and control system dynamics are numerically computed and used to update graphics and animation on the screen. The utility of the program for evaluating TLHS performance and teaching fundamental systems and control concepts is discussed.

The design of a decoupling compensator for the Apache helicopter is presented. The design is based on linear quadratic regulation with implicit model following. A decoupling compensator is designed for a reduced-order linear model of vehicle dynamics at hover using eigenstructure assignment. The resulting closed-loop system is used as a reference model in the design of a compensator for the full-order system, resulting in a constant state feedback matrix. A feedforward matrix (command mixer) is then designed to diagonalize the system at low frequencies. The design is evaluated with both the full-order linear model and a nonlinear simulation, ARMCOP. It is found to provide desired bandwidth and good decoupling properties with the linear model. The nonlinear simulation shows increased coupling due to the nonlinearities.

In this paper, a method is presented for governing the release of wafers (starts) into a re-entrant semiconductor fabrication line. A flow model for a five-machine six-step re-entrant mini-fab is used to present all developments. Stabilizing clear-a-fraction (CAF) state feedback policies are developed for the mini-fab. A systematic procedure is presented for regulating the flow of starts so that critical system constraints (e.g. machine availability and buffer level constraints, etc.) are never violated, however aggressive the release policy. The regulation is achieved via nonlinear optimization based on state information from the flow model. The resulting algorithm, called a release policy governor (RPG), is shown to produce a closed loop stable system.

The motivation for the work is aircraft guidance in a time controlled air traffic management system (ATM). This paper discusses two forms of optimal dynamic interpolation guidance (ODIG) and the effects of turbulence on its performance. The first form of ODIG is based on a cost functional that penalizes acceleration. The second form of ODIG penalizes both acceleration and velocaty excursion. Both have been applied to the L1011-100 vertical guidance problem in the presence of turbulence (the Dryden turbulence model was used). A flight management system's (FMS) vertical flight plan is used to obtain waypoints which serve as inputs to the ODIG algorithm. The algorithm produces reference commands which are issued to a certified FAA L1011-100 model and an autopilot. The resulting dynamic behavior is compared to the results obtained from reference commands produced by an L1011-like commercial aircaft's flight management system model (FMSM) under the same turbulence.

In this paper, dynamic interpolation is applied to an L1011-100 vertical guidance problem. A flight management system's (FMS) optimized vertical flight plan is used to obtain way points which serve as inputs to the dynamic interpolation algorithm. The algorithm produces reference commands which are issued to a model obtained from a certified FAA L1011-100 and autopilot. The resulting dynamic behavior is compared to the results obtained from reference commands produced by an L1011-like commercial aircraft FMS. Quadratic and cubic spline solutions to the dynamic interpolation problem are presented. Performance degradation with respect to weight uncertainty is examined for both the FMS and the Dynamic Interpolation commands.

This paper presents guidelines for developing a multivariable centralized automatic flight control system (AFCS) for a twin lift helicopter system (TLHS). Singular value ideas are used to formulate performarce and stability robustness specifications. A Linear-Quadratic-Gaussian with Loop Transfer Recovery (LQG/LTR) design is obtained and evaluated.

Direct sampled-data design techniques which use "lifting" concepts that capture the periodic structure of the sampled data system in order to obtain a tractable optimization problem that accommodates meaningful (weighted H/sup /spl infin//) closed loop performance specifications as well as sample rate and intersample behavior is proposed. Direct sampled-data design controller has similar complexity as discretized classical designs but operates at a much lower sampling rate. FPGA implementation data is presented for each design. Comparisons demonstrating the benefits of the sampled-data approach in achieving reasonable trade-offs are presented.