Topic
Rotational speed
About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.
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Patent•
17 Jul 2003
TL;DR: An apparatus and process for determining the absolute angular position of a rotating component can be found in this article, where one or more linear position sensors, such as a Hall-effect sensor, are placed near a degrading surface of a shaft or other rotating component.
Abstract: An apparatus and process for determining the absolute angular position of a rotating component. One or more linear position sensors (5), such as, for example, a Hall-Effect sensor, are placed near a degrading surface (6) of a shaft or other rotating component (11). The rotation of the shaft (11) varies the air gap between the sensor (5) and the degrading surface (6) thereby generating signals than can be processed to determine various operating parameters of the rotating shaft or component (11) such as the absolute angular position of the rotating shaft (11), the rotation speed of the shaft (11), and the acceleration of the rotating shaft (11).
33 citations
Patent•
25 Oct 1996
TL;DR: In this paper, a closed-loop control of an optical disk drive is proposed, where the disk motor servo determines the desired motor speed for a target track through a speed profile table.
Abstract: An optical disk drive in which changes in rotational speed are achieved under closed loop control, avoiding significant undershoots or overshoots in speed, increasing access time and reducing power. The speed control is suitable for use in a CLV system, in an CAV/CLV scheme, or in any system in which the speed of the disk must be changed at various times. Feedback from the motor, rather than data read from the disk, determines and controls motor speed during all search operations. The disk motor servo determines the desired motor speed for a target track through a speed profile table. The speed profile table can be designed to accommodate a combination of CAV mode and CLV mode of operation such that the disk drive system can run at the maximum data transfer rate permitted by the data processing electronics, or to minimize power consumption. Through closed loop control, the system ensures that the speed of the motor is quickly and accurately changed to the desired speed, typically by the time the optical pickup reaches a target track during a search operation. The closed loop control also allows the disk drive system to be designed for a lower tolerance level and still achieve jitter-free control. Thus the data rate can be increased due to the lower tolerance required. The access time is minimized because the CD-DSP can begin retrieving data as soon as the target track is reached, since the optical disk will generally already at the desired speed.
33 citations
TL;DR: In this paper, the authors adopted the CFD method to simulate the internal flow field of the cross flow fans (CFFs) and derived useful similarity laws related to the total pressure of the eccentric vortex center, total pressure rise between the entrance and the exit, and the impeller rotational speed.
33 citations
TL;DR: In this paper, the Ffowcs Williams-Hawkings equation was used for the analysis of rotating point sources and the deep difference between the acoustic fields generated by aeronautical and marine devices in air and underwater.
Abstract: This paper deals with the use of the Ffowcs Williams–Hawkings equation for hydroacoustic analysis of rotating blades, and the deep difference between the acoustic fields generated by aeronautical and marine devices in air and underwater. This dissimilarity does not depend on either the different fluid or the (although existing) geometric and structural difference of the blade: it is an intrinsic feature of the generating noise mechanisms related to rotating sources and is essentially due to the remarkable diversity of the rotational speed. It will be shown how the usual assumption of believing the flow nonlinear sources to be negligible for blades rotating at low subsonic speed (coming from decades of research strictly limited to aeroacoustics) is totally wrong when applied to hydroacoustics. Such a goal is achieved through a practical approach, by analysing the general behaviour of the surface integral kernels of the solution for a rotating point source (here named rotpole), and by showing its relationship with a general multibladed device. This analysis suggests that the underwater noise prediction from a marine propeller is an inherently nonlinear problem and, contrary to analogous aeronautical configurations, it always requires an accurate estimation of the nonlinear flow sources just by virtue of the very low rotational speed.
33 citations
23 May 2006
TL;DR: In this paper, the authors presented a new high speed induction machine coupled with a two-speed automatic shifting transmission in order to reduce size, weight and costs and to improve the efficiency.
Abstract: The electric machine combined with the transmission is a fundamental part of an electric vehicle. The paper presents a new high speed induction machine coupled with a two-speed automatic shifting transmission in order to reduce size, weight and costs and to improve the efficiency. Its rotation speed is up to 23000 rpm offering a high power density. Machine parameter and simulation results are given to show the potential benefits of a two speed gearbox. The new design is compared with traditional drive trains with fixed reduction ratio. A liquid cooling system using a small gap for the flow was designed in order to increase the continuous output power. The drive unit was built and examined on the test bench. It has been shown that high speed drives offer the possibility of further improvements of the electric traction system of road electric vehicles
33 citations