Aerospace Engineering Commons^™

Convergence Analysis Of Adaptive Critic Based Optimal Control, S. N. Balakrishnan, Xin Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive critic based neural networks have been found to be powerful tools in solving various optimal control problems. The adaptive critic approach consists of two neural networks which output the control values and the Lagrangian multipliers associated with optimal control. These networks are trained successively and when the outputs of the two networks are mutually consistent and satisfy the differential constraints, the controller network output produces optimal control. In this paper, we analyze the mechanics of convergence of the network solutions. We establish the necessary conditions for the network solutions to converge and show that the converged solution is optimal.

Infinite Time Optimal Neuro Control For Distributed Parameter Systems, S. N. Balakrishnan, Radhakant Padhi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The conventional dynamic programming methodology for the solution of optimal control, despite having many desirable features, is severely restricted by its computational requirements. However, in recent times, an alternate formulation, known as the adaptive-critic synthesis, has given it a new perspective. In this paper, we have attempted to use the philosophy of adaptive-critic design to the optimal control of distributed parameter systems. An important contribution of this study is the derivation of the necessary conditions of optimality for distributed parameter systems, described in discrete domain, following the principle of approximate dynamic programming. Then the derived necessary conditions of optimality are …

Cubesat: A New Generation Of Picosatellite For Education And Industry Low-Cost Space Experimentation, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A published article that included Professor Bob Twigga as an author "CubeSat: A new Generation of Picosatellite for Education and Industry Low-Cost Space Experimentation" from 2000.

Stanford University Space Programs: Program Time-Line, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Stanford University Space Programs: Program Time-Line" from 2000.

The Opal Satellite And Internet-Based Operations, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "The OPAL Satelliteand Internet-Based Operationshttp" from 2000.

Piezoceramic Actuator Placement For Acoustic Control Of Panels, Jeffrey S. Bevan

Mechanical & Aerospace Engineering Theses & Dissertations

Optimum placement of multiple traditional piezoceramic actuators is determined for active structural acoustic control of flat panels. The structural acoustic response is determined using acoustic radiation filters and structural surface vibration characteristics. Linear Quadratic Regulator (LQR) control is utilized to determine the optimum state feedback gain for active structural acoustic control. The optimum actuator location is determined by minimizing the structural acoustic radiated noise using a modified genetic algorithm. Experimental tests are conducted and compared to analytical results.

Anisotropic piezoceramic actuators exhibit enhanced performance when compared to traditional isotropic piezoceramic actuators. As a result of the inherent isotropy, these advanced …

Editorial, Ahmed Noor, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Carryover For Hypersonic '+' And 'X' Configuration Delta Fin Missiles, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Zonal Euler Solver code (ZEUS) is used to predict hypersonic missile flow fields and to determine the carryover factors for the effect of the body on wing lift, Kw(B), and for the effect of the wing on body lift, KB(w). Results are presented for Mach 4, 6, 8, and 10 at an angle of attack of 2 deg. The missile has a conical nose and a cylindrical fuselage with a 1-degree flair angle. Both 'x' and '+' fin configurations are considered. Results are given for 20 and 30 deg semi vertex angles as a function of fur span to …

Tuning Parameter Tolerance Design: Foundations, Methods, And Measures, Daniel A. Mcadams, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a novel technique is presented to solve tolerance design problems. To achieve the desired performance tolerance, the technique uses a subtle, but significant, change in the design: the addition of a tuning parameter in place of an increase in component precision. Statistical models are used to develop a framework for the tuning parameter design method. Also developed is a new, dimensionless design metric which ranks candidate tuning parameters. A step-by-step method is developed for the application of tuning parameters using this metric. The step-by-step tuning parameter design method is applied to a heavy-duty manual stapler as a …

Approximation Model Building For Reliability & Maintainability Characteristics Of Reusable Launch Vehicles, Resit Unal, W. Douglas Morris, Nancy H. White, Roger A. Lepsch, Richard W. Brown

Engineering Management & Systems Engineering Faculty Publications

This paper describes the development of parametric models for estimating operational reliability and maintainability characteristics for reusable launch vehicle concepts, based on vehicle size and technology support level. A reliability and maintainability analysis tool (RMAT) and response surface methods are utilized to build parametric approximation models for rapidly estimating operational reliability and maintainability characteristics such as mission completion reliability. These models that approximate RMAT, can then be utilized for fast analysis of operational requirements, for lifecycle cost estimating and for multidisciplinary design optimization.

Experimental Characterization Of Hygrothermal And Aging Effects In Textile Composites, Lokeswarappa R. Dharani, Samit Roy, V. Gupta, Weiqun Xu, N. Dixon

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper summarizes the hygrothermal and physical aging tests that were conducted on AS4/PR500 5HS textile composite laminates. The objectives of the hygrothermal tests were to determine the diffusivity and maximum moisture content of the laminate. Three temperatures and three relative humidity levels (RH) were used in combination to create seven test conditions. In addition, three stress levels and three damage levels were imposed to examine the combined effects of stress and damage on moisture absorption. Short-term creep tests were performed on neat resin at different test temperatures to characterize physical aging of the resin matrix. In addition, creep and …

Robust Adaptive Critic Based Neurocontrollers For Systems With Input Uncertainties, S. N. Balakrishnan, Zhongwu Huang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A two-neural network approach to solving optimal control problems is described in this study. This approach called the adaptive critic method consists of two neural networks: one is called the supervisor or critic, and the other is called an action network or controller. The inputs to both these networks are the current states of the system to be controlled. Each network is trained through an output of the other network and the conditions for optimal control. When their outputs are mutually consistent, the controller network output is optimal. The optimality is limited to the underlying model. Hence, we develop a …

Lifecycle Analysis For Environmentally Conscious Solid Freeform Manufacturing, Yanchun Luo, Ji Zhiming, Ming-Chuan Leu, R. J. Caudill

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A lifecycle based process model for analyzing the environmental performance of SFM processes and SFM based rapid tooling processes is presented in this paper. The process environmental performance assessment model considers material, energy and disposal scenarios. The material use, process parameters (e.g. scanning speed) and power use can affect the environmental consequence of a process when material resource, energy, human health and environmental damage are taken into account. The presented method is applied to the SLA process and two SLA based rapid tooling processes. The method can be used to compare different rapid prototyping (RP) and RT processes in terms …

Reverse Engineering Of Foreign Missiles Via Genetic Algorithm, Jon D. Wollam

Theses and Dissertations

One mission of the National Air Intelligence Center (NAIC) is the reverse engineering of foreign missile weapon systems from incomplete observational data. In the past, intuition and repeated runs of a missile performance model were required to converge to a solution compatible with observed flight characteristics. This approach can be cumbersome and time consuming, as well as being subject to undesirable influences from the analyst's preconceptions and biases. An alternative approach has been created to apply genetic algorithm (GA) techniques to allow automation of the process, wider exploration of the design space, and more optimal solutions matching the observational data. …

Effects Of Foreign Object Damage From Small Hard Particles On The High-Cycle Fatigue Life Of Ti-6a1-4v, Joseph L. Hamrick Ii

Theses and Dissertations

Thin rectangular samples of Ti-6Al-4V were damaged by four methods to represent foreign object damage found in turbine engine blades: 1) impact with 2 mm and 5 mm diameter glass spheres at 305 m/s, 2) impact with 2 mm and 4 mm diameter steel spheres at 305 m/s, 3) quasi-static displacement controlled indentation using steel chisels with 1 mm, 2 mm and 5 mm diameter tips and 4) shearing notches with a 2 mm diameter chisel point under a quasi-static loading condition. Finite element analysis was used to study the relationship between the stress state created by the plastic damage …

Current Design - Structure And Layout, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Current Design - Structure and Layout" from November 30, 1999.

Opal Press Release: October 28, 1999, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A press release written by Professor Bob Twiggs titled "Opal Press Release: October 28, 1999."

Opal Microsatellite, Greg Hutchins

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Greg Hutchins on the "OPAL Microsatellite" from October 8, 1999.

Student Space Program: Stanford University, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Student Space Program: Stanford University" from October 3, 1999.

An Intermittent-Combustion General Aviation Aircraft Engine Exhaust Noise Prediction Algorithm, Hiroko Tada

Master's Theses - Daytona Beach

From an environmental point of view, the reduction of aircraft noise has become an important factor recently. There are two factors that make airplane noise: propeller noise and engine noise. This report puts emphasis on only the engine noise in order to begin understanding what airplane engine exhaust noise is. At first, the engine exhaust noise is comprehended using the Dobrzynski's engine noise theory. Next, a discussion about an Embry-Riddle Aeronautical University (ERAU) engine system, engine exhaust system configurations, and microphone setting standards that show the ERAU engine system exhaust noise data. Finally, an Intermittent-Combustion (IC) General Aviation (GA) aircraft …

Suppression Of Post-Buckling Deflection And Panel-Flutter Using Shape Memory Alloy, Mohammad Tawfik Abo El So-Oud

Mechanical & Aerospace Engineering Theses & Dissertations

A novel concept proposed is the use of Shape Memory Alloy (SMA) to reduce the panel thermal deflection and flutter responses. SMA has unique ability to recover large prestrains completely when the alloy is heated (by aerodynamic heating in the present case) above the austenite start temperature A_s. During the recovery process, a large tensile recovery stress occurs if the SMA is restrained.

In this thesis, a panel subject to the combined aerodynamic and thermal loading is investigated. A nonlinear finite element model based on von Karman strain displacement relation is utilized to study the effectiveness of SMA …

An Improved Thermal Mass Flow Controller For Hazardous And Precision Applications, William J. Alvesteffer

Mechanical & Aerospace Engineering Theses & Dissertations

A new mass flow controller has been designed which responds very rapidly to changes in control settings. The design was evolved after carefully studying the internal flow and the sources for thermal lag and other non-linear behavior. After discussing an overview of the basic mass flow controller operating principles, data will be presented which characterize the basic building blocks of an advanced flow sensor design. Subsequently, a flow model and control strategy have been developed and tested which reduce response lag significantly. Results of the new design, obtained experimentally under various transient conditions, will be discussed.

Darpa Mems Demonstration In Systems Of Dod Relevance, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "DARPA MEMS Demonstration in Systems of DoD Relevance" from October of 1999.

Effect Of Interfacial Mobility On Flexural Strength And Fracture Toughness Of Glass/Epoxy Laminates, T. W. H. Wang, Frank D. Blum, Lokeswarappa R. Dharani

Chemistry Faculty Research & Creative Works

Mechanical testing and surface fractography were used to characterize the fracture of E-glass fiber reinforced epoxy composites as a function of the silane coupling agent used. gamma-Aminopropyltriethoxysilane (APS) and delta-aminobutyltriethoxysilane (ABS) were used because these have been shown to have different interfacial mobilities at multilayer coverage. The values of the properties studied generally increased from untreated c, as determined from a Mode I translaminar fracture toughness tests, for the untreated composites (10.5 ± 0.4 kJ/m2) was lower than that for the ABS-treated composites (14.3 ± 2.1 kJ/m2) which was lower than that for the APS-treated composites (17.1 ± 2.4 kJ/m2). …

Long-Term Aircraft Structural Integrity Prediction Under The Influence Of Feedback Control, Si-Bok Yu

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis investigates the influence of feedback control, and other factors associated with loading characteristics, on fatigue damage reduction and long-term integrity of aircraft structural components. An actively controlled flexible aircraft model and a new state space modeling procedure for crack growth are utilized to uncover important factors which influence airframe crack growth. A matrix of simulation test cases is constructed to cover such variables as open-loop operation, nominal closed-loop operation, perturbed closed-loop operation (i.e., feedback gain variation), nominal maneuver profile, perturbed maneuver profile (including overload strength and frequency), atmospheric gust, and mean stress level. Simulation output data including crack …

Microsatellite And Formation Flying Technologies On University Nanosatellites, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A published article that included Professor Bob Twiggs as an author titled "Microsatellite and Formation Flying Technologies on University Nanosatellites" from September 28, 1999.

Arliss: Student Payload Rocket Launch, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A report believed to have been written by Professor Bob Twiggs on the "Student Payload Rocket Launch" from September 10-11, 1999.

The Conference Proceedings Of The 1999 Air Transport Research Group (Atrg) Of The Wctr Society, Volume 3, Anming Zhang, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 99-7

The Conference Proceedings Of The 1999 Air Transport Research Group (Atrg) Of The Wctr Society, Volume 4 , Anming Zhang, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 99-8

Space-Available Transportation: An Analysis Of The Cost Of Providing 'Free' Travel, Frank J. Long

Theses and Dissertations

The purpose of this study is to estimate the costs borne by the government for providing space-available travel to eligible uniformed services personnel and their dependents. As the primary provider of the space-available privilege, it is important that the Air Force have an estimate of the burden that the administration of that privilege places on the budget. In January 1993, the Air Force discontinued its 15-year-old practice of charging a fee for space-available travel aboard AMC-owned or controlled aircraft. The fee had been set at $10 in 1978 and was collected to recover a portion of the costs associated with …