Vibration isolation under isolator-structure interaction

This thesis analyses a general case of the vibration isolation (VI) problem, considering both a rigid and non-rigid supporting structures. The aim is to study changes on the behaviour of both systems isolators and supporting structure when the interaction phenomenon between them is considered. The influence of the VI task on the base response is evaluated. In addition, the effect of the base dynamics on the the VI and alignment problem is studied. The novel contribution to the knowledge of this thesis is formulation of a novel VI approach, which facilitates a holistic analysis of the problem considering all the systems involved on it. This approach is valid for any number of isolators and for any type of base structure. Moreover, different control objectives can be easily defined; evaluation of the interaction phenomenon on both the platform and base response for different VI techniques; demonstration of the importance of the isolator damping ratio on the influence that the VI task has on the base response; evaluation of the effects of the supporting structure dynamics on the VI and alignment problem when multiple isolators are involved; analysis of the Multiple-Input-Multiple-Ouput (MIMO) control strategy by comparison with the Single-Input-Single-Output (SISO) control strategy. This comparative has been made for the VI and alignment problem of multiple isolators on a non-rigid supporting structure and includes analysis of the effectiveness of the Coral Reefs Optimization algorithms to find nearly-optimal control gains in VI and alignment problems. Through the investigation made for this thesis, a number of significant results have been reached, which show the importance of the supporting structure dynamics on the VI and alignment task. Moreover, the interaction phenomenon, and its consequence on the base response, has been investigated experimentally. The results derived from this thesis conclude that, for most scenarios, the dynamics of the base affects the VI task. Also, the active VI (AVI) technique shows a greater influence on the base response than passive VI (PVI) technique, for most cases. It has been observed that the use of AVI technique can additionally be oriented to control vibrations of the supporting structure, while the VI task is developed. Significant differences have been found when multiple isolators are involved in the same task for the alignment and VI problem, depending on whether or not the dynamics of the base are considered. The best set of control gains for the rigid-support case (which lead to maximum damping ratio) differ from those obtained when the supporting structure is considered as a flexible system, for different cases analysed in this thesis. The MIMO control strategy has shown great improvement with respect to the use of the SISO control strategy. Also, the Coral Reefs Optimization algorithms have been demonstrated to be a suitable tool to find nearly-optimal solutions for this type of problems

The NASA SBIR product catalog

The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

CLiFF Notes: Research In Natural Language Processing at the University of Pennsylvania

The Computational Linguistics Feedback Forum (CLIFF) is a group of students and faculty who gather once a week to discuss the members\u27 current research. As the word feedback suggests, the group\u27s purpose is the sharing of ideas. The group also promotes interdisciplinary contacts between researchers who share an interest in Cognitive Science. There is no single theme describing the research in Natural Language Processing at Penn. There is work done in CCG, Tree adjoining grammars, intonation, statistical methods, plan inference, instruction understanding, incremental interpretation, language acquisition, syntactic parsing, causal reasoning, free word order languages, ... and many other areas. With this in mind, rather than trying to summarize the varied work currently underway here at Penn, we suggest reading the following abstracts to see how the students and faculty themselves describe their work. Their abstracts illustrate the diversity of interests among the researchers, explain the areas of common interest, and describe some very interesting work in Cognitive Science. This report is a collection of abstracts from both faculty and graduate students in Computer Science, Psychology and Linguistics. We pride ourselves on the close working relations between these groups, as we believe that the communication among the different departments and the ongoing inter-departmental research not only improves the quality of our work, but makes much of that work possible

Aeronautical engineering: A continuing bibliography with indexes (supplement 304)

This bibliography lists 453 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors