No description available.

This thesis presents an investigation into the problems of exploration, map building and collision free navigation for intelligent autonomous mobile robots. The project began with an extensive review of currently available literature in the field of mobile robot research, which included intelligent control techniques and their application. It became clear that there was scope for further development with regard to map building and exploration in new and unstructured environments. Animals have an innate propensity to exhibit such abilities, and so the analogous use of artificial neural networks instead of actual neural systems was examined for use as a method of robot mapping. A simulated behaviour based mobile robot was used in conjunction with a growing cell structure neural network to map out new environments. When using the direct application of this algorithm, topological irregularities were observed to be the direct result of correlations within the input data stream. A modification to this basic system was shown to correct the problem, but further developments would be required to produce a generic solution. The mapping algorithms gained through this approach, although more similar to biological systems, are computationally inefficient in comparison to the methods which were subsequently developed. A novel mapping method was proposed based on the robot creating new location vectors, or nodes, when it exceeded a distance threshold from its mapped area. Network parameters were developed to monitor the state of growth of the network and aid the robot search process. In simulation, the combination of the novel mapping and search process were shown to be able to construct maps which could be subsequently used for collision free navigation. To develop greater insights into the control problem and to validate the simulation work the control structures were ported to a prototype mobile robot. The mobile robot was of circular construction, with a synchro-drive wheel configuration, and was equipped with eight ultrasonic distance sensors and an odometric positioning system. It was self-sufficient, incorporating all its power and computational resources. The experiments observed the effects of odometric drift and demonstrated methods of re-correction which were shown to be effective. Both the novel mapping method, and a new algorithm based on an exhaustive mesh search, were shown to be able to explore different environments and subsequently achieve collision free navigation. This was shown in all cases by monitoring the estimates in the positional error which remained within fixed bounds.

Angles measurements from optical systems are the primary source of data for maintaining the orbits of high altitude satellites. Radar measurements are used primarily for low Earth orbit (LEO) satellites. Recently it has been shown that the accuracy of the orbit updates using only optical system angles-only data is just as good, if not better, than the performance from radar systems for LEO satellites. The purpose of this thesis is to investigate the use of optical angles data with and without laser ranging data in determining the trajectories of missiles. Analytical Graphics, Inc. Satellite Tool Kit is used to model the trajectory of a ballistic missile. Several scenarios are developed for determining the orbit when acquired by sensors providing various combinations of range, range rate and angles data. It is found that the combination of range, azimuth and elevation sensor data yields an orbit determination that has enough merit to be called accurate. The error of the orbit determined by the angles-only data is two orders of magnitude larger than the error of the range and angles measurement. Additionally completed was an analysis of what would happen if the sensors could only track to the maximum altitude of the orbit. As was assumed, the known position of the object drifts ranged from minimal to significant predicated on the final known position. This is indicated by the error ellipsoid. It was again found that the combination of range, azimuth and elevation sensor data until the maximum altitude yields an orbit determination that has enough merit to be called accurate. Also considered was the addition of a second sensor that had the capacity to always track range, azimuth and elevation to increase the time that is afforded to track the object, increasing the overall accuracy of the orbit determination. It is found that the addition of a second sensor increases the fidelity of the angles-only measurement such that the combination of azimuth and elevation sensor data yields an orbit determination that has enough merit to be called accurate.

We describe major enhancements to the missile defense planning aid "JOINT DEFENDER" (JDEF). JDEF is the first system that shows how to evaluate and exploit new and anticipated improvements in interceptors, long-range surveillance and tracking capabilities, networked communications, and the ability of detecting platforms to cue intercepting ones downrange. We want to improve system-wide effectiveness, gauged here by the reduction of expected damage inflicted. We defend an asset list (DAL) of targets, characterized by their locations and values to us. Our defenders include pure "LOOKERs," radars and sensors of enemy missile launches, and "SHOOTERs," platforms with means to both detect and intercept enemy launches. JDEF optimally positions platforms that can be moved, and prescribes what each platform should do. JDEF can estimate the value to either opponent of secrecy, deception, or intelligence. JDEF is the only missile defense planning system using formal optimization. Among many advantages this conveys, JDEF is able to unambiguously quantify the difference among disparate plans. Although the JDEF planner can manually control any detail, the planner is well advised to let optimization suggest where to start.

A near-optimal guidance law has been developed using the direct method of calculus of variations that maximizes the kinetic energy transfer from a surface-launched missile upon interception to a ballistic missile target during the boost phase of flight. Mathematical models of a North Korean Taep'o-dong II (TD-2) medium-range ballistic missile and a Raytheon Standard Missile 6 (SM-6) interceptor are used to demonstrate the guidance lawâ s performance. This law will utilize the SM-6â s onboard computer and active radar sensors to independently predict an intercept point, solve the two-point boundary value problem, and determine a near-optimal flight path to that point. Determining a truly optimal flight path would require significant computing power and time, while a near-optimal flight path can be calculated onboard the interceptor and updated in real time without significant changes to the interceptorâ s hardware. That near-optimal guidance path is then converted into a set of command functions and fed back into the control computer of the interceptor. By modifying the second and third derivatives of the two-point boundary value problem, the intercept conditions can be varied to study their effects upon the optimal flight path regarding the maximization of kinetic energy upon impact. / US Navy (USN) author.

Thesis (M.M.E.)--Boston University. / Statement of the problem. It was the purpose of this study (1) to clarify some desirable objectives and procedures for guiding and motivating children's growing musical perceptions through listening; and (2) to suggest ways of presenting selected music literature in the primary and intermediate grades in such a way that it implements these objectives and encourages growth in perceptive listening. Methods and procedures. Basically, a library research study, the sources of data included a review of current literature in music education and general elementary education. Books, periodicals, yearbooks, and publications of learned societies were consulted, as well as books on music and musicians. Special emphasis was given to books written specifically for children and teachers. Other works consulted were master's theses and doctoral dissertations [TRUNCATED]

Thesis. 1975. Sc.D.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Vita. / Bibliography: leaves 318-319. / Sc.D.

The thesis presents a critique of the nature of 13 to 15 year-old students' images of futures. Arguments are made for their importance to the individual community and culture and their value and use in a science learning setting.This study of the nature of futures images is based upon data collected from small samples in two school settings between 1990 and 1999 using a guided fantasy approach. The diversity of student hopes and fears for futures is categorised using several research tools developed from the futures literature. The results identify a range of futures scenarios ranging from highly utopic to highly dystopic and themes including human interactions, the natural and built environment and the nature and use of futuristic technologies.The importance of student images of futures is discussed from the personal perspective of the students and then considered in the broader context of society and Western culture. The data are examined through a number of theoretical frames including psychology, history and the futures field of enquiry. The consensus seems to be that expectations of the future are inseparable from human nature and influential in determining the viability of cultures.The value of student images of futures in science learning is explored through a case study of one of my own Year 9 classes. In teaching this class I used the technique of futures imaging integrated into a critical futures teaching approach utilising a constructivist planning model. I found that students' futures images revealed a broader aspect of student worldviews than is usual in science learning environments, and were valuable in exposing student prior knowledge, interests and concerns. Student learning seemed to be enhanced using this futures oriented approach.

Traditional simulation languages and simulators do not fully support the need to design, modify, and extend simulation models of manufacturing systems, especially, material handling systems. Since AGV systems, one type of automated material handling systems, require complicated control logic, flexible job routings, and frequent layout modifications and extensions to correspond to production requirements, the time consumption and efforts to achieve the above tasks in traditional paradigms are significant. However, such difficulties can be overcome by the use of object-oriented simulation. This research develops an object-oriented modeling architecture for the simulation of AGV (automated guided vehicle) systems by extending Beaumariage's object-oriented modeling environment (1990) which is originally designed for the simulation of job shop type manufacturing systems. For this extension, several classes required to comprise an AGV system are created into the original environment which include AGV, limited size queue, control point, track segment, machine cell, AGV system control classes, and so on. This architecture provides a flexible environment that enables the modeling of traditional and tandem AGV system layouts. A best-first search approach, one artificial intelligence search algorithm, is employed to direct AGVs to determine the shortest path from all possible travel paths. The computerized modeling system with this conceptual architecture is easy to use, especially compared with traditional simulation tools. In addition, the extended object-oriented architecture used for the simulation of AGV systems is program independent and may be implemented in any object-oriented language. The prototype system implemented as a portion of this research is performed in Smalltalk/V. Two case examples are presented for verification and validation. / Graduation date: 1996

In this study, to discuss the effect of the boundary between pipeline and clamp support changed by different pressures to the propagation of guided wave in the pipeline is the main idea. In addition, the author simulates the wave propagation situation by using finite element method. In this work, T(0,1) torsional mode was used to discuss when adding different pressures to the clamp support, the change of its reflection coefficients in different frequencies by the axial symmetric property propagates in the cylinder pipe. In the simulation, we take the ¡§fictitious layer¡¨ was used to describe the situation between the clamp support and pipeline when adding different pressures. Moreover, the stiffness normal to the fictitious layer and the stiffness parallel to the fictitious layer were taken as material parameters to achieve the situation between clamp support and pipeline. According to experimental results, when the torque increases, the reflection coefficients will decrease with increasing frequency. The reflection coefficients are about 0.08 to 0.02. By the result of experiment and simulation, one can know that when adding torque on the clamp support increases, the reflection coefficient will decrease. In addition, the author also prove that if we change the stiffness parallel to the fictitious layer material factor, then the T(0,1) guided wave will be more sensitive by its action of particle motion.