Topic
Critical speed
About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.
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TL;DR: In this article, an active control scheme based on the transfer function model is proposed to suppress the vibration of a disk spinning both in the sub- and super-critical speed ranges, where the point sensor can measure both the displacement and the pitching slope of the spinning disk.
9 citations
Patent•
08 Feb 2007
TL;DR: In this paper, the running speed of a relevant vehicle is monitored against a speed limit change pattern to enhance the safety of train operation at low cost without installing ground equipment and an emergency brake is automatically activated when the speed limit is exceeded for a predetermined warning period.
Abstract: PROBLEM TO BE SOLVED: To enhance the safety of train operation at low cost without installing ground equipment. SOLUTION: It is monitored whether or not the running speed of a relevant vehicle is higher than a speed limit by checking it against a speed limit change pattern. When the running speed of the relevant vehicle exceeds the speed limit, a warning alarm is outputted. When the speed limit is successively exceeded for a predetermined warning period, an emergency brake is automatically activated. Further, it is monitored whether or not the running speed of the relevant vehicle is higher than a critical speed by checking it against a critical speed change pattern. When the running speed of the relevant vehicle exceeds the critical speed, the emergency brake is immediately activated regardless of whether or not the warning period has passed. COPYRIGHT: (C)2007,JPO&INPIT
9 citations
TL;DR: In this article, the authors investigated the characteristics of motion fire in one-train and multiple-train tunnels with longitudinal ventilation and established the critical speed model and applied it to one train tunnel and multiple train tunnel scenarios.
9 citations
TL;DR: In this article, the single objective optimization and the multi-objective optimization for a flexible rotor system with magnetic bearings are presented, where the design variables are the cross-sectional area of the shaft, the bias currents of magnetic bearings, and the positions of the disk and the magnetic bearings.
Abstract: This paper presents the single objective optimization and the multi-objective optimization for a flexible rotor system with magnetic bearings. The weight of rotor shaft and the transmitted forces at the magnetic bearings are minimized either individually or simultaneously under the constraints on the critical speeds and the control currents of magnetic bearings. The design variables are the cross-sectional area of the shaft, the bias currents of magnetic bearings, and the positions of the disk and the magnetic bearings. The dynamic characteristics are analyzed using the generalized polynomial expansion method and the sensitivity analysis is also studied. For single objective optimization, the method of feasible directions (MFD) is applied. For multi-objective optimization, the weighting method (WM), the goal programming method (GPM), and the fuzzy method (FM) are employed. It is found that the system design can be significantly affected by the choices of the bias currents of magnetic bearings, the position of the disk with unbalance, and the magnetic bearings. The results also show that a better compromised design can always be obtained for multi-objective optimization.
9 citations
15 Mar 1988-JSME international journal. Series 3, Vibration, control engineering, engineering for industry
TL;DR: In this article, the amplitude curve and the phase angle curve were measured in the neighborhood of the major critical speed for various angular positions of the rotor unbalance, and it was shown that the shape of the resonance curve changes extremely due to the direction of the unbalance.
Abstract: In order to find some way to detect a transverse crack due to fatigue in a rotating machine, we have investigated experimentally and theoretically the change in the resonance curve caused by the occurrence of a crack. The experimental apparatus is a vertical rotating shaft system in which an elastic shaft with a disk is supported simply at both ends. In experiments, the amplitude curve and the phase angle curve were measured in the neighborhood of the major critical speed for various angular positions of the rotor unbalance. The results show that the shape of the resonance curve changes extremely due to the direction of the unbalance, and an unstable region appears when the unbalance exists in the same direction as the crack. It is shown that this phenomenon is explained theoretically by combining the characteristics of the unsymmetrical shaft and that of the symmetrical shaft or by considering rotating nonlinear spring characteristics.
9 citations