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 paper, a finite element analysis using 3-D isoparametric 20 noded elements was carried out to find a simple, practical and sufficiently accurate method for finding the natural frequencies of a propeller shaft assembly.
17 citations
TL;DR: In this article, the effects of gyroscopics on rigid rotor AMB systems were quantified in terms of translation mode and tilt mode dimensionless eigenvalues and eigenvectors.
Abstract: Most industrial rotors supported in active magnetic bearings (AMBs) are operated well below the first bending critical speed. Also, they are usually controlled using proportional, integral and derivative controllers, which are set up as modally uncoupled parallel and tilt rotor axes. Gyroscopic effects create mode splitting and a speed-dependent plant. Two AMBs with four axes of control must simultaneously control and stabilize the rotor/AMB system. Various analyses have been published considering this problem for different rotor/AMB configurations. There has not been a fully dimensionless analysis of these rigid rotor AMB systems. This paper will perform this analysis with a modal PD controller in terms of translation mode and tilt mode dimensionless eigenvalues and eigenvectors. The number of independent system parameters is significantly reduced. Dimensionless PD controller gains, the ratio of rotor polar to transverse moments of inertia and a dimensionless speed ratio are used to evaluate a fully general system stability rigid rotor analysis. An objective of this work is to quantify the effects of gyroscopics on rigid rotor AMB systems. These gyroscopic forces reduce the system stability margin. The paper is also intended to help provide a common framework for communication between rotating machinery designers and controls engineers
17 citations
TL;DR: In this paper, the authors used the additional slope and bending moment at crack position to analyze the dynamic behavior of a general cracked rotor, which results in the harmonic vibration, is simulated using the response including bending moment and additional slope recursively.
17 citations
TL;DR: In this paper, an experimental facility conforming to the proposed topology, with a particular focus on the control problem such a system presents, is presented in the form of H $_\infty$ -based control.
Abstract: This paper demonstrates vibration reduction in a hollow rotating shaft by means of internal-stator active magnetic actuators, which are resiliently mounted This problem requires further consideration over and above classic rotor/magnetic bearing systems on account of the flexible behavior of the magnetic actuator support structure This paper presents an experimental facility conforming to the proposed topology, with a particular focus on the control problem such a system presents The unique challenges are discussed, and a solution is presented in the form of H $_\infty$ -based control Ultimately, experimental results demonstrate the system to be capable of substantial rotor vibration suppression, including while passing the rotor's first critical speed, which was not obtainable with simpler classical control techniques This means the top achievable rotor speed was increased from approximately 3000 r/min without magnetic actuator vibration suppression to over 9000 r/min with vibration suppression active At the rotor critical speed, the magnetic actuators affect a reduction in rotor vibration amplitude of over 70% compared to the rotor supported purely on mechanical bearings, while simultaneously avoiding excessive excitation of the flexible active magnetic actuator support structure
17 citations
TL;DR: In this paper, the dynamics of shaft-rotor systems, where the shaft profiles are contoured, are considered. And the response of the system for particular shaft and rotor dimensions and rotational speeds is determined, establishing the dynamic characteristics in the vicinity of the whirling speed.
17 citations