Aerospace Engineering Commons^™

Genericity And Singularities Of Robot Manipulators, Ming-Chuan Leu, D. K. Pai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The kinematic singularities of robot manipulators are studied from the point of view of the theory of singularities. The notion of a "generic'' kinematic map, whose singularities form smooth manifolds of prescribed dimension in the joint space of the manipulator, is examined. For three-joint robots, an equivalent algebraic condition for genericity using the Jacobian determinants is derived. This condition lends itself to symbolic computation and is sufficient for the study of decoupled manipulators. Orientation and translation singularities of manipulators are studied in detail. A complete characterization of orientation singularities of robots with any number of joints is given. The translation …

Moving Object Recognition And Guidance Of Robots Using Neural Networks, Abhijit Neogy, S. N. Balakrishnan, Cihan H. Dagli

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The design of a robust guidance system for a robot is discussed. The two major tasks for this guidance system are the online recognition of a moving object invariant to rotation and translation, and tracking the moving object using a neural-network-driven vision system. This system included computer software ported to the IBM PC and interfaced with an IBM 7535 robot. The operation of this guidance system involved recognition of a moving object and the ability to track it till the robot and effector was in close proximity of the object. It was found that the robot was able to track …

Extension Of Vlasov’S Semi-Membrane Theory To Reinforced Composite Shells, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Governing equations for the statics and dynamics of reinforced composite shells are developed based on Vlasov's semi-membrane shell theory. These equations have closed-form solutions illustrated for buckling and free vibration problems. The buckling solution converges to the known result for unstiffened isotropic shells. © 1992 by ASME.

Consideration Of Phase Transformations In The Study Of Shear Bands In A Dynamically Loaded Steel Block, Z. G. Zhu, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We study plane strain thermomechanical deformations of a square block made of steel and model a material defect in it by a rigid non-heat-conducting ellipsoidal inclusion located at the center of the block. The boundaries of the block are presumed to be thermally insulated, and its top and bottom surfaces compressed vertically at a prescribed rate. The loading pulse is assumed to be made up of three parts; an initial segment in which the speed increases from zero to the steady value, the steady part, and the third part in which the speed decreases gradually to zero and is maintained …

Machining Of Composite Materials. Part I: Traditional Methods, Serge Abrate, D. A. Walton

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Composite materials are more difficult to machine than metals mainly because they are anisotropic, non-homogeneous and their reinforcing fibers are very abrasive. During machining, defects are introduced into the workpiece, and tools wear rapidly. Traditional machining techniques such as drilling or sawing can be used with proper tool design and operating conditions. A review of traditional machining methods applied to organic and metal matrix composites is presented in this article. The use of non-traditional machining methods such as waterjet, laser and ultrasonic machining will be discussed in the second part. © 1992.

Machining Of Composite Materials. Part Ii: Non-Traditional Methods, Serge Abrate, D. Walton

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Machining of composite materials is difficult due to the heterogeneity and heat sensitivity of the material and the high abrasiveness of the reinforcing fibers. This results in damage being introduced into the workpiece and very high tool wear. The use of traditional machining methods was reviewed in Part I of this paper. Here new methods are considered: laser, waterjet, electro-discharge, electro-chemical spark, and ultrasonic machining. These various techniques have been applied to organic matrix composites with aramid, glass, graphite fiber reinforcement but also to metal matrix and ceramic matrix composites. © 1992.

Effect Of Temperature On The Ultimate Strength And Modulus Of Whisker‐Reinforced Ceramics, Douglas R. Carroll, Lokeswarappa R. Dharani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Whiskers are a very attractive means of reinforcing a ceramic material. It has been shown that the whiskers dramatically improve the ultimate strength and modulus of the materials at room temperature. However, recent studies indicate that at high temperatures the improvement is less pronounced, or there is no improvement at all. In this paper a model is developed to explain why the properties are degraded at high temperature. The parameters which seem most important for high‐temperature performance are the coefficients of thermal expansion and Poisson's ratios for the constituents, the heat treatment temperature, and the coefficient of friction between the …

Analysis Of Shear Bands In Simple Shearing Deformations Of Nonpolar And Dipolar Viscoplastic Materials, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

During the past few years, we have studied numerically the initiation and growth of shear bands in nonpolar and dipolar viscoplastic materials being deformed in simple shear, and in nonpolar materials undergoing plane strain deformations. We summarize here our work for the former problem. © 1992 American Society of Mechanical Engineers.

Hierarchical Neurocontroller Architecture For Robotic Manipulation, Xavier J. R. Avula, Luis C. Rabelo

Chemical and Biochemical Engineering Faculty Research & Creative Works

A hierarchical neurocontroller architecture consisting of two artificial neural network systems for the manipulation of a robotic arm is presented. The higher-level network system participates in the delineation of the robot arm workspace and coordinates transformation and the motion decision-making process. The lower-level network provides the correct sequence of control actions. A straightforward example illustrates the architecture''s capabilities, including speed, adaptability, and computational efficiency

Fourier Transform Infrared (Ftir) Spectroscopy Analysis Of Combustion Aerosol, Gary Jacquin

Opportunities for Undergraduate Research Experience Program (OURE)

In conjunction with my co-op program at McDonnell-Douglas, my current OURE project is the analysis of combustion aerosols using Fourier Transform Infrared (FTIR) Spectroscopy. Aerosol science is a very important field as it is concerned with atmospheric chemistry, atmospheric physics, climate, public health, and environmental issues.

In the Cloud and Aerosol Sciences Laboratory (CASL) at UMR, combustion aerosols are generated by an in-house designed torch or burner. The fuels, JP4 and JP5, are provided by McDonnell-Douglas. Some other commercial fuels are also used. The primary objective of my OURE project was to generate and collect combustion aerosols for chemical analysis. …

A Computer Graphics Program For Displaying Water Molecules On A Dn3500 Apollo Workstation, Michael A. Stuller

Opportunities for Undergraduate Research Experience Program (OURE)

A computer graphics program is developed for displaying water molecule configurations on the screen of a DN3500 Apollo workstation. The motivation was to generate a fast display of output from molecular dynamics or Monte Carlo computer simulations. Input to the program consists of a listing of the Cartesian coordinates of the atomic constituents of the molecules. Options in the program include: 1) number of molecules; 2) plot size; 3) atomic radii; 4) superposition of substrate atomic positions; 5) viewing angle; and 6) color-coded and/or numbered atoms. The program is written in Fortran.

Modeling For Supersonic Missile Wing-Body Interference Lift, Howard S. H. Ho

Opportunities for Undergraduate Research Experience Program (OURE)

During the initial phase of a missile design, a quick and simple way of estimating wing-body interference is essential. A simple panel model based on the cross flow over a cylinder is developed to estimate the effect of the body on the wing lift This model produces quick and reasonably accurate results, while little user expertise is needed. This model determines K_WB (upwash interference factor) and K_Φ (sideslip interference factor), and is applicable to infinitely thin delta and clipped delta fins on missiles in supersonic flight. The effects of the fin semivertex angle, span, taper ratio, free stream …

Development Of A Large Commercial Transport Model For A Real-Time Digital Flight Simulator, John Francis Winkler

Opportunities for Undergraduate Research Experience Program (OURE)

In order to test the adaptability of the University of Missouri-Rolla's flight simulator to different types of aircraft, a basic mathematical model of a large commercial transport aircraft is developed. The original aircraft model is based on the Cessna 210, and in order to accommodate the drastic differences between the Cessna 210 and the Boeing 747, many changes are made to the simulation code. The aircraft geometric data, stability and control derivatives, and weights data are altered to match those of the 747. Changes are made within the various subroutines to include thrust reversal, spoilers, and a variable incidence horizontal …

Some Stability And Control Aspects Of A Variable Pivot Wing Configuration, Paul Vitt

Opportunities for Undergraduate Research Experience Program (OURE)

In supersonic flight, there is a large positive shift in the static margin, which causes extreme positive shifts in longitudinal stability, and is an undesirable characteristic. This paper investigates some of the stability and control aspects of an alternative configuration, that of a variable pivot wing aircraft -- an aircraft with two sets of wings, one set sweeps forward, the other set sweeps rearward. By prescribing a sweep schedule, it is desired to minimize the static margin shift with Mach number. The effects of the two lift elements -- that of mechanical shift of the center of pressure forward with …

Development Of A Learjet Model 24d For The Umr Flight Simulator, Richard Stigall

Opportunities for Undergraduate Research Experience Program (OURE)

A flight simulator was recently developed at the University of Missouri-Rolla for a single engine aircraft. The need soon arose for a higher performance aircraft. After exploring several possibilities, a Learjet Model 24D was chosen to include the high performance aircraft.

The purpose of this project was to develop a model for the Learjet 24D. This was accomplished by examining the computer code previously written and determining the changes needed. The code for the simulation is located in various subroutines. Each subroutine was analyzed to determine if changes needed to be made. When a modification was needed, appropriate methods were …

Computer Visualization Of Irrotational Flow Over Bluff And Streamlined Bodies, Nora Okong' O

Opportunities for Undergraduate Research Experience Program (OURE)

Computer programs were developed to visualize irrotational flow over bluff bodies (circular cylinders and half-bodies) and streamlined bodies (elliptical cylinders and airfoils). The method of superposition of flows was used, with stream functions or complex velocity potentials for fundamental flows being added to obtain the flows over the bodies. For the flow over the circular cylinders, half-bodies and elliptical cylinders, the stream function was calculated directly. The flow over the airfoil was obtained by Joukowski mapping of the imaginary part of the complex velocity potential for flow over a circular cylinder.

The programs developed will be valuable learning tools for …

Vertical And Angular Motion Of A Wing Model In Steady Flow: A Physical And Numerical Experimental Study, Andrew P. Johnston

Opportunities for Undergraduate Research Experience Program (OURE)

The dynamic response of a rigid wing in steady flow mounted on translational and rotational elastic supports is investigated. This study presents both a numerical and a physical experimental arrangement that can be employed to investigate the effect of a wide range of parameters on the response of the wing subjected to steady flow. An interactive computer program, which utilizes the fourth order Runge-Kutta integration scheme to solve the governing differential equations, is discussed. The program output allows for quick visualization of the change in response due to parameter changes. An experimental arrangement that utilizes the new 18" x 18" …

Implementation Of The Articulated Total Body (Atb) Model On An Apollo Workstation, M. F. Laudon

Opportunities for Undergraduate Research Experience Program (OURE)

The Articulated Total Body Model (ATB) is used for predicting gross segmented body response in various dynamic environments. The ATB computer program, originally written by the Department of Transportation as a Crash Victim Simulation (CVS) program, was later modified by the Calspan Corporation and More recently by the Armstrong Aerospace Medical Research Laboratory (AAMRL) to allow for aerodynamic force applications, harness belt capabilities and hyper-ellipsoidal graphical display of the modeled segments. The ATB model has been successfully used to investigate gross human body responses to bodies placed in such complex dynamic environments as high-speed aircraft ejection. This ATB model is …

Petri Net Modeling Of A Flexible Assembly Station For Printed Circuit Boards, M. Zhou, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Petri net modeling approaches are presented for a flexible workstation for automatic assembly of printed circuit boards. In order to improve the productivity of such a system, the building of mathematical models is a crucial step. Concentrating on the operational aspects, the authors construct ordinary and temporal Petri net models for the AT&T FWS-200 physical flexible workstation. Three outcomes follow from such models. First, designers can have a better understanding of concurrency, synchronization, mutual exclusion, and sequential relations involved in the system control from the graphical representations of Petri nets. Second, the performance analysis of system operations under different settings …

Intelligent Control Of A Robotic Arm Using Hierarchical Neural Network Systems, Xavier J. R. Avula, Luis C. Rabelo

Chemical and Biochemical Engineering Faculty Research & Creative Works

Two artificial neural network systems are considered in a hierarchical fashion to plan the trajectory and control of a robotic arm. At the higher level of the hierarchy the neural system consists of four networks: a restricted Coulomb energy network to delineate the robot arm workspace; two standard backpropagation (BP) networks for coordinates transformation; and a fourth network which also uses BP and participates in the trajectory planning by cooperating with other knowledge sources. The control emulation process which is developed using a second neural system at a lower hierarchical level provides the correct sequence of control actions. An example …

Hierarchical Neurocontroller Architecture For Intelligent Robotic Manipulation, Xavier J. R. Avula, Luis C. Rabelo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A hierarchical neurocontroller architecture consisting of two artificial neural network systems for the manipulation of a robotic arm is presented. The higher-level neural system participates in the delineation of the robot arm workspace and coordinates transformation and the motion decision-making process. The lower one provides the correct sequence of control actions. The capabilities, including speed, adaptability, and computational efficiency, of the developed architecture are illustrated by an example.

Decoupled Dynamics For Control And Estimation, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Decoupling of the dynamical equations in polar coordinates is used to develop a control scheme for use in target-intercept problems with passive measurements. By defining a pseudo control variable in the radial coordinate, the radial dynamics is made independent of the transverse dynamics. After solving for the radial control, the transverse control is determined through solutions to a two-point boundary value problem. Numerical results from a six degree-of-freedom simulation which used the decoupled control indicate that it is better than the completely Cartesian coordinate control for most of the cases considered. Decoupled control, though, is obtained iteratively through a two-point …

Analysis Of Shear Banding In Plane Strain Compression Of A Bimetallic Thermally Softening Viscoplastic Body Containing An Elliptical Void, Z. G. Zhu, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We study plane strain thermomechanical deformations of a prismatic viscoplastic body of square cross-section and deformed at a nominal strain-rate of 5000 s-1. The body has two thin layers placed symmetrically about the horizontal centroidal axis and an elliptical void at the center. The major axis of the void coincides with the vertical centroidal axis and also with the direction of loading. The layer material differs from that of the body in only the value of the yield stress in a quasistatic simple compression test. The yield stress for the layer material is taken to be either one-fifth or five …

Impact On Laminated Composite Materials, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laminated composite materials are used extensively in aerospace and other applications. With their high specific modulus, high specific strength, and the capability of being tailored for a specific application, these materials offer definite advantages compared to more traditional materials. However, their behavior under impact is a concern, since impacts do occur during manufacture, normal operations, or maintenance. The situation is critical for impacts which induce significant internal damage, undetectable by visual inspection, that cause large drops in the strength and stability of the structure. Impact dynamics, including the motion of both the impactor and the target and the force developed …

Matrix Cracking In Laminated Composites: A Review, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This article presents an overview of the problem of matrix cracking in laminated composite materials. The parameters governing the onset and accumulation of internal damage under several types of loadings are reviewed. The analysis of laminates with matrix cracks can be performed using a shear-lag model, variational, elasticity, finite element or finite difference approaches. Prediction of further cracking is based on either a fracture mechanics approach or a probabilistic failure strength theory. Continuum damage mechanics are used by some investigators to model the behavior of the cracked laminate. Recent developments in this area are summarized here, and suggestions for future …

Dynamic Adiabatic Shear Band Development In A Bimetallic Body Containing A Void, R. C. Batra, Z. G. Zhu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We study the problem of the initiation and subsequent growth of a shear band in a thermally softening viscoplaslic prismatic body of square cross-section and containing two symmetrically placed thin layers of a different viscoplastic material and an elliptical void at the center. The yield stress of the material of the thin layer in a quasistatic simple compression test is taken to be either five times or one-fifth that of the matrix material. The body is deformed in plane strain compression at a nominal strain rate of 5.000 s '. These deformations are assumed to be symmetrical about the centroidal …

Parallel Implementation Of A Recursive Least Squares Neural Network Training Method On The Intel Ipsc/2, James Edward Steck, Bruce M. Mcmillin, K. Krishnamurthy, M. Reza Ashouri, Gary G. Leininger

Computer Science Faculty Research & Creative Works

An algorithm based on the Marquardt-Levenberg least-square optimization method has been shown by S. Kollias and D. Anastassiou (IEEE Trans. on Circuits Syst. vol.36, no.8, p.1092-101, Aug. 1989) to be a much more efficient training method than gradient descent, when applied to some small feedforward neural networks. Yet, for many applications, the increase in computational complexity of the method outweighs any gain in learning rate obtained over current training methods. However, the least-squares method can be more efficiently implemented on parallel architectures than standard methods. This is demonstrated by comparing computation times and learning rates for the least-squares method implemented …

Thermoelastic Problems Of Multilayered Cylinders, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Thermoelastic problems of long multilayered cylinders manufactured from isotropic materials are considered. The steady-state thermal field corresponding to a constant difference between temperature outside and inside the assembly is used in the analysis. Both the case of a hollow cylinder and that of a solid multilayered assembly are discussed. A closed-form exact solution is shown for an arbitrary number of layers if the properties of constituent materials remain unaffected by temperature. Various strategies leading to an analytical solution are proposed for the case where material properties depend on temperature. The stresses in a dual-coated optical fiber subject to a uniform …

Robust Nonlinear Control Of Brushless Dc Motors In The Presence Of Magnetic Saturation, N. Hemati, J. S. Thorp, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A robust control law is derived and examined for a direct-drive robot arm driven by a brushless DC motor (BLDCM). The complete dynamics of the motor and its interaction with the robot arm are accounted for. This is important, since in a direct-drive servo system the torque generated by the motor is directly transmitted to the load. Effects of magnetic saturation as well as reluctance variations are accounted for, in order to ensure accuracy. The effectiveness of the method is examined through computer simulations. The computational complexity of the overall control scheme is such that it can be readily used …

Thermal Dynamic Problems Of Reinforced Composite Cylinders, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Thermal dynamic problems of circular cylindrical composite shells reinforced in the axial and circumferential directions and subject to variations of temperature are considered. Nonlinear governing equations are formulated based on the extension of Donnell shell theory. These equations are used to determine the response of geometrically nonlinear and linear shells to a thermal loading represented by the Heaviside step function (thermal shock). The solution of the nonlinear problem obtained by the assumption that displacements are single-term functions of coordinates is discussed. The analysis of the linear problem illustrates different types of response to thermal shock. The condition of thermally induced …