Rotating reference frame

Summary

A rotating frame of reference is a special case of a non-inertial reference frame that is rotating relative to an inertial reference frame. An everyday example of a rotating reference frame is the surface of the Earth. (This article considers only frames rotating about a fixed axis. For more general rotations, see Euler angles.) Fictitious forces Fictitious force All non-inertial reference frames exhibit fictitious forces; rotating reference frames are characterized by three:

the centrifugal force,
the Coriolis force, and, for non-uniformly rotating reference frames,
the Euler force.

Scientists in a rotating box can measure the speed and direction of their rotation by measuring these fictitious forces. For example, Léon Foucault was able to show the Coriolis force that results from Earth's rotation using the Foucault pendulum. If Earth were to rotate many times faster, these fictitious forces could be felt by humans, as they are when on a spinning carousel. R

Official source

https://en.wikipedia.org/wiki/Rotating_reference_frame

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Dynamic stall has been a limiting factor in design and operation on rotating systems within the rotorcraft, propulsion, and sustainable energy disciplines for more than forty years, impacting operational performance and component fatigue. In the last decade, significant advances have been accomplished in the understanding, prediction, modeling, and control of dynamic stall on both static and rotating wings. In September 2019, an Army Research Officefunded workshop was held at the Georgia Institute of Technology to evaluate the state of the art and future directions in the understanding and control of dynamic stall. Approximately forty attendees drawn from top experts in the field to graduate students convened to discuss experimental, computational, theoretical, and control research in the field over a two-day period. This workshop was designed to gather the details of these advances and to impart to the broader community the current state of the art in the understanding and prediction of dynamic stall for rotating systems. A summary of the discussions and findings from this workshop are presented here.

2020

Decoupled dq-Current Control of Grid-Tied Voltage Source Converters Using Nonparametric Models

Behrooz Bahrani, Alireza Karimi, Alfred Rufer

This paper presents a vector control strategy for regulating the current of grid-tied voltage source converters (VSCs) in a rotating reference frame. The proposed approach is based on shaping the open-loop and closed-loop transfer matrices of the system. Solving a constrained convex optimization problem, the shaping is achieved, which guarantees the stability of the closed-loop system. The designed controller results in the desired dynamic performance and decouples the direct and quadrature (dq) current axes. The structure of the proposed controller is similar to that of its predecessors and consists of four proportional-integral controllers. The performance of the method is evaluated based on simulation and experimental results. It is confirmed that its dynamic performance is better than that of the previously proposed approaches, and it results in the decoupled current axes.

Institute of Electrical and Electronics Engineers2013

Coherence transfer in nuclear magnetic resonance by selective homonuclear Hartmann-Hahn correlation spectroscopy

Geoffrey Bodenhausen, Robert Konrat

New NMR techniques are described for transferring transverse magnetization between scalar-coupled nuclei in the rotating frame. The methods involve simultaneous spin-locking of two selected spins A and X, using cosinusoidal modulation of the radio frequency (rf) carrier. If transverse magnetization of spin A is excited selectively before spin-locking, for example with a self-refocusing 270 Deg Gaussian pulse, in-phase magnetization will be transferred from spin A to spin X, and in-phase multiplets are obtained in both one- and two-dimensional spectra. The method allows one to verify whether two particular spins are connected by a scalar coupling. Examples are shown for peptides and basic pancreatic trypsin inhibitor (BPTI). The fine structure of the multiplets yields information on couplings to further spins. In contrast to nonselective spin-lock expts., the magnetization cannot diffuse to a manifold of coupling partners. If relayed coherence transfer is to be achieved deliberately, several spins may be locked simultaneously by imposing an addnl. modulation on the rf carrier. [on SciFinder (R)]

1991