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Mechanical and Aerospace Engineering Faculty Research & Creative Works
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Full-Text Articles in Mechanical Engineering
Compliant Pliers, Ashok Midha, S. C. Visser
Compliant Pliers, Ashok Midha, S. C. Visser
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The pliers include an endless loop, a top jaw appended to the endless loop, and a bottom jaw appended to the endless loop. The endless loop includes in series a top grip handle, a spring segment, a bottom grip handle and a compliant strip interconnecting the top and bottom grip handles. A rolling surface on the top grip handle rolls on a contact portion of the bottom grip handle. The rolling action causes the compliant strip to flex which causes the top and bottom jaws to move toward one another. The endless loop provides a built-in automatic spring and enhances …
A Dual Neural Network Architecture For Linear And Nonlinear Control Of Inverted Pendulum On A Cart, S. N. Balakrishnan, Victor Biega
A Dual Neural Network Architecture For Linear And Nonlinear Control Of Inverted Pendulum On A Cart, S. N. Balakrishnan, Victor Biega
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The use of a self-contained dual neural network architecture for the solution of nonlinear optimal control problems is investigated in this study. The network structure solves the dynamic programming equations in stages and at the convergence, one network provides the optimal control and the second network provides a fault tolerance to the control system. We detail the steps in design and solve a linearized and a nonlinear, unstable, four-dimensional inverted pendulum on a cart problem. Numerical results are presented and compared with linearized optimal control. Unlike the previously published neural network solutions, this methodology does not need any external training, …
Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier
Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An infrared extinction technique was used to characterize spatially and temporally the vapor phase of a transient fuel spray. Optical extinction data were taken at two laser wavelengths and compared to obtain fuel vapor partial pressure values averaged over the line-of-sight through the spray. A transient fuel injector spray was characterized at several axial positions with a spatial resolution of 0.125 cm and a temporal resolution of 0.2 ms. With the knowledge of an axisymmetric spray pulse, the line-of-sight averaged results were deconvoluted to obtain spatially resolved vapor pressure data. The same spray was also characterized using phase/doppler interferometry to …
Effect Of Inflow Pressure And Wall Heat Transfer On Shock-Induced Combustion/Detonation, B. S. Green, Harlan F. Nelson
Effect Of Inflow Pressure And Wall Heat Transfer On Shock-Induced Combustion/Detonation, B. S. Green, Harlan F. Nelson
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Oblique detonation waves are possible ignition mechanisms for scramjet engines. Results from a numerical study of the effects of changing the inflow pressure on oblique detonation wave structure for supersonic flow of a stoichiometric hydrogen-air mixture over a flat plate followed by a ramp are presented. Viscous effects and finite-rate chemistry are considered. Inflow pressure is varied from 0.1 to 1 atmosphere for Mach 4 inflow over a 30-degree ramp. Also, the effect of wall heat transfer rate is examined by comparing adiabatic wall, and constant temperature wall solutions. A separation bubble forms at the intersection of the flat plate …
Radiative Heating In Scramjet Combustors, Harlan F. Nelson
Radiative Heating In Scramjet Combustors, Harlan F. Nelson
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Currently, there is considerable interest in scramjet engines for hypersonic aircraft and missiles. This paper presents preliminary calculations of the radiative heating of the walls of scramjet combustion chambers. The analysis assumes isothermal, constant property flow fields which are representative of actual combustor flow fields. The fuel is H2 and N2 is taken as inert. Temperature in the combustor is on the order of 2000 to 3000 K and pressure is of the order of 5 atm. The combustion products consist mainly of H2O and OH. These gases are strong radiators in the infrared. Radiation heating can be significant because …
Non-Axisymmetric Matrix Cracking And Interface Debonding With Friction In Ceramic Composites, F. S. Ji, Lokeswarappa R. Dharani
Non-Axisymmetric Matrix Cracking And Interface Debonding With Friction In Ceramic Composites, F. S. Ji, Lokeswarappa R. Dharani
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An three-dimensional analytical model based on the principle of minimum potential energy is developed and applied to determine the stress state in a discrete fiber/matrix composite cylinder subjected to axial tensile loading in the fiber direction and containing a non-symmetric transverse matrix crack and an interface debond. The friction over the debonded interface is incorporated into the analysis. The strain energy release rates associated with the matrix crack and the interface debonding under the combination of the applied load and the interface frictional force are computed. The strain energy release rate criterion has been employed to evaluate the critical applied …
Hamiltonian Based Adaptive Critics For Missile Guidance, S. N. Balakrishnan, Jie Shen
Hamiltonian Based Adaptive Critics For Missile Guidance, S. N. Balakrishnan, Jie Shen
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A Hamiltonian based adaptive critic structure is proposed for solving missile guidance problems. This structure consists of a supervisor neural network called 'critic' and a controller network called 'action'. Together they are used to solve model-based guidance problems. The advantage of this approach is that: i) the training data for each network is created by the other network, ii) the converged solutions yield near optimal guidance over the entire span of the training range, and iii) they can be used as feedback controllers though trained off-line. A main contribution is that we establish a direct link between traditional optimal control …
A Class Of Modified Hopfield Networks For Aircraft Identification And Control, Jie Shen, S. N. Balakrishnan
A Class Of Modified Hopfield Networks For Aircraft Identification And Control, Jie Shen, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a class of modified Hopfield neural networks and their use in solving aircraft optimal control and identification problems. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problems under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions are discussed. Energy minimization of the networks leads to identification of the system parameters. Numerical results are provided to identify the dynamics of an aircraft, and the corresponding optimal control is calculated online. Comparison of the …
Target Profile Estimation Using Haar Functions, William R. Bockman, S. N. Balakrishnan, Christopher D'Souza, James Cloutier
Target Profile Estimation Using Haar Functions, William R. Bockman, S. N. Balakrishnan, Christopher D'Souza, James Cloutier
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An approach to estimating the target acceleration in a maneuvering target model using Haar function partial summations to model the target acceleration is developed. A kinematic constraint is applied to the maneuvering target model and the effects of the use of this constraint are reviewed.
Heat Transfer In Two-Phase Solid-Rocket Plumes, Harlan F. Nelson, John C. Fields
Heat Transfer In Two-Phase Solid-Rocket Plumes, Harlan F. Nelson, John C. Fields
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Results of a direct simulation Monte Carlo (DSMC) and free molecule (FM) analysis of convective heat transfer to Al2O3 particles in solid-rocket plume environments are presented. The particle diameters are assumed to be 4μm, and the plume gases are CO2, H2O, CO, and N2. The plume gas temperature is 2000 K. Particle temperatures of 1500, 2000, and 2500 K are investigated for Knudsen numbers from 1/2 to 1000 (from slip flow to FM flow). The Nusselt number is presented in terms of Knudsen number and Reynolds number (or relative velocity). Both the Kavanau and the Kashmarov and Svirshevskii correlations generally …
A Finite Element Model Of Thermoacoustic Oscillations In Rayleigh Flow, Carlos A. Gutierrez, Walter Eversman
A Finite Element Model Of Thermoacoustic Oscillations In Rayleigh Flow, Carlos A. Gutierrez, Walter Eversman
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The work reported here describes a portion of the development of a finite element model of thermoacoustic oscillations in ducted flows, including three dimensional geometries and nonuniform mean flows with steady heat addition. The thermoacoustic problem is not modeled by a form of the convected wave equation but instead by the conservation equations in primitive form. In this paper the three-dimensional model is reduced to one dimension, applicable to a uniform geometry, but allowing an axially nonuniform flow with sharp gradients in temperature, density, and Mach number. The steady mean flow is computed as a Rayleigh flow. Calculations are shown …
Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett
Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A model based on similarity transformation, for the nitrogen-diluted, H2-air opposed-jet laminar counterflow diffusion flame (CFDF), was developed independently of earlier models, and numerically solved to study flame location and flame structure and extinction limits. Numerical stiffness is handled by a special treatment of the species production term. Flame location with respect to the stagnation plane is identified as an important parameter that governs H2-air diffusion flames, and physical explanations are given to show how flame location is affected by fuel dilution, strain rate, and Lewis number. Results show very good agreement with experimental extinction conditions. The effect of thermal …