Digital Commons Network^™

A Sensory-Based Adaptive Walking Control Algorithm For Variable Speed Biped Robot Gaits, Andrew L. Kun

Doctoral Dissertations

A balance scheme for handling variable speed gaits was implemented on an experimental biped. The control scheme used pre-planned but adaptive motion sequences in combination with closed loop reactive control. CMAC neural networks were responsible for the adaptive control of side-to-side and front-to-back balance. The biped performance improved with neural network training. The biped was able to walk with variable speed gaits, and to change gait speeds on the fly. The slower gait speeds required statically balanced walking, while the faster speeds required dynamically balanced walking. It was not necessary to distinguish between the two balance modes within the controller. …

Modeling Of The Electromagnetic Radiation From Shielded Enclosures With Apertures And Attached Wires In A Real-World Environment, Bruce Roy Archambeault

Doctoral Dissertations

A hybrid modeling technique using the Finite-Difference Time-Domain (FDTD) approach in conjunction with the Method of Moments (MoM) approach was developed to allow simulation of electromagnetic interference (EMI) emissions through apertures due to sources within a shielded enclosure. These apertures can include air ventilation openings, option card slots, mating cover seams, or any other opening in the metal shielded enclosure. Modeled emission results can now be directly compared to U.S. and other countries' regulations to allow engineers to predict compliance before hardware prototypes are built. The effects of the test environment, including ground plane and specified measurement distance, as well …

An Experimental Investigation Of The Effects Of Elastic Modulus And Yield Strength On Fracture Surface Interference In Shear Loaded Cracks, Ronald U. Goulet

Doctoral Dissertations

An experimental process was developed to study the effects of material properties on fracture surface interference in Mode II loaded cracks in 7075 aluminum. 4340 and 8642 steels. Factors studied included elastic modulus, yield strength, mode mixity and fracture surface geometry. An asymmetric four point bend specimen and fixture was developed to apply pure Mode II and mixed Mode I and II loads to edge cracks. Three dimensional displacement fields were measured as a function of applied load using an electro-optical holographic interferometric facility. Stress intensity factors were obtained by fitting observed 2-D field displacements to basis functions derived from …

Dynamic Response Of Poroelastic Materials Containing Bingham Fluid: Application To Electrorheological Fluids, Mete Kesan

Doctoral Dissertations

This work examines the dynamic response to harmonic loading of a disk of poroelastic material containing non-Newtonian Bingham fluid which exhibits a yield stress. Biot's poroelasticity equations and modified Darcy's law for non-Newtonian fluids exhibiting a yield stress are combined together to obtain the governing equations of the system for quasi-static case. Dissipation due to friction arising from the flow of fluid relative to the solid is taken into account but inertia effects are neglected. The response and the complex modulus of the system are calculated using the finite element method taking into account the nonlinear nature of Bingham fluid. …

Numerical Analysis For Blood Distribution In Complete Flow Cross-Section Microvascular Networks, Jewen Xiao

Doctoral Dissertations

As the blood flows through a bifurcation, the axisymmetric red blood cell concentration profile is skewed by plasma skimming. In the downstream segment of the bifurcation the concentration profile of red blood cells recovers symmetry by the red blood cell dispersion process.

In this study, the concentration convective equation, which models the red blood cell dispersion process, is solved with the method of finite differences in cylindrical coordinates. In the computation, a shear-induced diffusivity coefficient is used. The computed hematocrit ratios at the second bifurcation are compared with in vitro experimental data obtained from 50 $\mu$m serial trees with two …

An Experimental Investigation Of Thermally-Induced Deformation Of 1 Micron Thick Copper/Tantalum/Polymide High-Density Interconnect Structures, Dmitry V. Zhmurkin

Doctoral Dissertations

A new technique to estimate the out-of-plane thermal expansion coefficient (CTE) of several 1 $\mu$m thick, spin-coated polyimides is introduced. Arrays of parallel copper and polyimide lines of various aspect ratios on Si substrate were imaged in air at room temperature and at 97$\sp\circ$C using an atomic force microscope (AFM). The out-of-plane CTE of the polyimides was estimated by matching the experimental results with the predictions of finite element models with different out-of-plane parameters. For FPI-135 (6FCDA-TMOB) polyimide the out-of-plane CTE was found to be $\approx$260 ppm/$\sp\circ$C, for FPI-136 (PMDA-6FDA-TFMOB) polyimide $\approx$120 ppm/$\sp\circ$C. Polyimide lines with widths equal to or …