Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / M.S.

The present paper is related to the problem of approximating the exact solution to the magnetohydrodynamic equations (MHD). The behaviour of a viscous, incompressible and resistive fluid is exemined for a long period of time. Contents: 1 The magnetohydrodynamic equations 2 Notations and precise functional setting of the problem 3 Existence, uniqueness and regularity results 4 Statement and Proof of the main theorem 5 The approximate inertial manifold 6 Summary

In the thesis, we present the structures of interacting multiple model (IMM) algorithm-based filter design for real-time motion orientation estimation and tracking by using inertial sensor measurements in three-dimensional space. The major sensor such as gyroscope, though has high-sensitivity characteristics, suffers from bias build-up and error drift over time. The complementary sensors such as accelerometer and magnetometer, on the other hand, have low sensitivity, but do not suffer from bias problems. By using individual inertial and magnetic sensors, measurements of multiple modes can be interactively computed. The IMM based designs show the advantages of weighting individual sensors in different motion states. We propose a signal processing architecture based on the IMM algorithm. It is composed of three parallel Kalman filters (KFs), each deals with measured signals from accelerometer, magnetometer and gyroscope, respectively. The accelerometer cannot effectively sense the rotation around the vertical axis; while the magnetometer can only sense the rotation around vertical axis. Therefore, estimation accuracy with the parallel filtering arrangement of the IMM algorithm-based structure may be affected. A scheme using the residual signal, which is computed in the IMM, provides the information of gyroscope-based KF to the other two filters for feasible calculation of update weights. Related research also usually combined the information of major and complementary sensors in estimator designs. In the literature, existing ¡§Triad¡¨ methods with quaternion-based extended Kalman filter (EKF), process the measurements from major and complementary sensors. To compensate the functions, we propose to use a gyroscope-based EKF and a Triad EKF in forming a parallel multiple model-based structure. The analysis and performance evaluation shows advantages and disadvantages of using EKFs and KFs in IMM-based filtering approachs. Simulation results validate the proposed estimator design concept, and show that the scheme is capable of reducing the overall estimation errors by flexible computation of model weights.

The effect of finite Reynolds numbers on chaotic advection is investigated for two dimensional lid-driven cavity flows that exhibit topological chaos in the creeping flow regime. The emphasis in this endeavor is to study how the inertial effects present due to small, but non-zero, Reynolds number influence the efficacy of mixing. A spectral method code based on the Fourier-Chebyshev method for two-dimensional flows is developed to solve the Navier-Stokes and species transport equations. The high sensitivity to initial conditions and the exponentional growth of errors in chaotic flows necessitate an accurate solution of the flow variables, which is provided by the exponentially convergent spectral methods. Using the spectral coefficients of the basis functions as solved through the conservation equations, exponentially accurate values of velocity everywhere in the flow domain are obtained as required for the Lagrangian particle tracking. Techniques such as Poincare maps, the stirring index based on the box counting method, and the tracking of passive scalars in the flow are used to analyze the topological chaos and quantify the mixing efficiency.

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Accurately determining one’s location has long been a persistent problem in navigation and has reappeared in recent years in the field of mobile computing. The ability to determine a device’s location indoors is needed for both automation and efficient communication in collaborative robotic and sensor networks. Technologies such as indoor GPS transmitters and Cricket have been employed, but have had limited success due to cost, accuracy, and power consumption. The Inertial Solution for Accurately Assessing location Coordinates (ISAAC) was developed as a means of filling this need without requiring infrastructure or expensive components to accurately determine position, inside or outside. ISAAC is based on modified six-degrees-of-freedom (6DOF) dead reckoning algorithms currently being used by Unmanned Aerial Vehicles (UAV). UAVs typically have access to other types of sensors to supplement and/or replace the IMU measurements. ISAAC was implemented using a low-cost MEMS 6DOF IMU in which the onboard firmware was modified to incorporate the dead reckoning calculations and communications necessary to realize ISAAC. ISAAC was implemented as a portable unit which communicated with a host computer through an RS-232 interface. ISAAC did not perform as well as expected; the location coordinates were very inconsistent with device movements and did not produce any useful data. The correct intermediate results of the calculations and subsequent review by a local subject-matter-expert implies that the source of the erroneous results lie with the accuracy and precision of the MEMS IMU. ISAAC presents a foundation for future work where more robust sensors and/or filtering can be used for further examination of inertial-based location systems. / text

Inertial measurement units (IMUs) are used in a wide range of applications to estimate position, velocity, and attitude of vehicles. The high cost of tactical grade IMUs makes the low-cost microelectromechanical systems (MEMS) based IMUs appealing. These types of IMUs are less accurate, so to counteract this effect, multiple and different configurations should be used. The work presented here provides efficient and low cost solutions using different configurations of redundant (multiple) MEMS-IMU swarms, which increase the level of accuracy to potentially the order of that of a tactical IMU. Several configurations are presented and compared through different methods. / text

Despite a recent focus on understanding cumulative load, researchers still prefer to analyze the data using mean and peak values. At the same time, technological advancements have provided biomechanists with methods of collecting large amounts of data pertaining to joint loading. Waveform analysis offers another option that will become increasingly relevant, as wireless data collection devices become common place and provide access to waveforms from many hours of recording. The overall objectives of this research were to demonstrate some of the limits of current methods of biomechanical analysis, and introduce an alternative, and secondly, to propose a wireless system for use in field-based studies. An exploratory study using Functional Data Analysis (FDA) was completed on experimental lifting data. The results demonstrated that FDA can elucidate subtle differences in the curve shape outside of the peak areas typically used for statistical analysis that were attributed to fatigue. These findings support the need for a better understanding of how workers change their movement strategies as time progresses throughout the length of the workshift. To achieve this type of knowledge, a wireless data collection device utilizing inertial motion sensors (IMS) was introduced and validated for field use in the remaining three chapters. The IMS units in conjunction with an anthropometric model were tested against a traditional link segment model recorded in a gold-standard, video system. Testing that occurred in the entire reach space volume yielded errors as low as 5% for the lumbar moment, but errors also greatly exceeded 50% RMS error in some cases. Three hand switch alternatives were tested for their potential to provide external hand force timing and duration information to the link segment model, but none were found to be perfectly suitable in the current configuration. In conclusion, a wireless system based on IMS units has the potential to provide long-term data collection, but the development of the calibration routines and complexity of the underlying model must be improved. FDA was shown to have good potential for identifying subtle differences in curve shapes, and may become useful when long-term field-based data are readily available with the proposed IMS system. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2009-04-21 09:01:22.968

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 25, 2008) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.