Chattering-free sliding mode control with unidirectional auxiliary surfaces for miniature helicopters

Purpose – This article proposes a chattering-free sliding mode control scheme with unidirectional auxiliary surfaces (UAS-SMC) for small miniature autonomous helicopters (Trex 250). Design/methodology/approach – The proposed UAS-SMC scheme consists of a nested sequence of rotor dynamics, angular rate, Euler angle, velocity and position loops. Findings – It is demonstrated that the UAS-SMC strategy can eliminate the chattering phenomenon exhibiting in the convenient SMC method and achieve a better approaching speed. Originality/value – The proposed control strategy is implemented on the helicopter and flight tests clearly demonstrate that a much better performance could be achieved, compared with convenient SMC schemes

Bibliography of Lewis Research Center technical publications announced in 1989

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1989. All the publications were announced in the 1989 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Technical accomplishments of the NASA Lewis Research Center, 1989

Topics addressed include: high-temperature composite materials; structural mechanics; fatigue life prediction for composite materials; internal computational fluid mechanics; instrumentation and controls; electronics; stirling engines; aeropropulsion and space propulsion programs, including a study of slush hydrogen; space power for use in the space station, in the Mars rover, and other applications; thermal management; plasma and radiation; cryogenic fluid management in space; microgravity physics; combustion in reduced gravity; test facilities and resources

NASA Tech Briefs, February 1987

Topics include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Fabrication Technology; Machinery; Mathematics and Information Sciences; Life Sciences

Aeronautical engineering: A continuing bibliography with indexes (supplement 301)

This bibliography lists 1291 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 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

Aeronautical engineering: A cumulative index to a continuing bibliography (supplement 248)

This publication is a cumulative index to the abstracts contained in Supplements 236 through 247 of Aeronautical Engineering: A Continuing Bibliography. The bibliographic series is compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). Seven indexes are included -- subject, personal author, corporate source, foreign technology, contract number, report number and accession number

Aeronautical engineering: A continuing bibliography with indexes (supplement 231)

This bibliography lists 469 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1988

Aeronautical engineering: A continuing bibliography with indexes (supplement 233)

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1988. 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

The transmission of vibration by the human body with special reference to the problems of measurement and analysis

Modern forms of transportation can impose high levels of vibration upon their occupants. If one is concerned with the welfare and comfort of the passengers, or the ability of the pilots or drivers to perform their respective tasks in such an environment, then clearly one needs to be able to define the vibration levels experienced by such people. This definition must not only quantify the input levels but also include the levels measured at that part of the human body which will be most affected by the vibration. This thesis therefore covers work aimed at determining the frequency response of the human body under vibration conditions and presents amplitude ratio and phase angle plots of head, and shoulder, accelerations/seat acceleration against frequency for various postures and limb positions. [Continues.

Comics and/as Documentary: the implications of graphic truth-telling

Examining examples from a cluster of early twenty-first century comics this thesis argues that these are comics adopting a documentary mode of address. The recognition that they share a documentary ambition to visually narrate and represent aspects and events of the real world, in turn calls for a closer examination of the contribution such comics present in terms of documentary’s repertoire. This thesis challenges the persistent assumption that ties documentary to recording technologies, and instead engages an understanding of the category in terms of narrative, performativity and witnessing. In so doing, it aligns with debates and questions raised by recent academic work around animated documentary. Shared concerns include conventions, truth-claims and trust, and the limitations of representation as verisimilitude. Mindful not to overstate correspondence with animated and inherently moving image forms, however, this contribution explicitly concerns documentary in comics form: as constituted by static and silent pages. The enquiry is structured according to concerns and themes that have been identified as central to documentary theory: the relation between documentary image and its referent; the production of archives and popular history; the social function of documentary as visibility and ‘voice’, and the travelogue as cultural narrative and production of knowledge. In other words, examples of comics that address actual, as opposed to imagined, persons and events of the historical world, are read through the lens of documentary. Close reading and visual analysis, engaging comics-specific frameworks, asks how comics by means of their formal qualities might offer alternative strategies and even the possibility to overcome certain problems associated with audiovisual modes of documentary representation. The thesis simultaneously extends an alternative perspective to literary frameworks, in particular the categories of memoir and autobiography, which have come to dominate in a steadily growing field of comics studies