63 resultados para Crane, Richard Teller, 1832-1912.
em Doria (National Library of Finland DSpace Services) - National Library of Finland, Finland
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Kirje 9.4.1973
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Doctoral dissertation, University of Helsinki
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Zusammenfassung: Kirchliche Praktiken und der nationale Wohlstand : die Auffassung Richard Hookers (1554-1600) über das Wesen und die Bedeutung der Kirchenordnung Elisabeth I
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Abstract: "Freedom before the thruth - Richard Rorty's pargamtist apology for liberal human rights"
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The improvement of the dynamics of flexible manipulators like log cranes often requires advanced control methods. This thesis discusses the vibration problems in the cranes used in commercial forestry machines. Two control methods, adaptive filtering and semi-active damping, are presented. The adaptive filter uses a part of the lowest natural frequency of the crane as a filtering frequency. The payload estimation algorithm, filtering of control signal and algorithm for calculation of the lowest natural frequency of the crane are presented. The semi-active damping method is basedon pressure feedback. The pressure vibration, scaled with suitable gain, is added to the control signal of the valve of the lift cylinder to suppress vibrations. The adaptive filter cuts off high frequency impulses coming from the operatorand semi-active damping suppresses the crane?s oscillation, which is often caused by some external disturbance. In field tests performed on the crane, a correctly tuned (25 % tuning) adaptive filter reduced pressure vibration by 14-17 % and semi-active damping correspondingly by 21-43%. Applying of these methods require auxiliary transducers, installed in specific points in the crane, and electronically controlled directional control valves.
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Helsinki 1912
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Helsinki 1912
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Helsinki 1912
