Instant centre of rotation
In Fig. P is the point of rotation
The instant center of rotation (also known as instantaneous velocity center, instantaneous center, or pole of planar displacement) of a body undergoing planar movement is a point that has zero velocity at a particular instant of time. At this instant, the velocity vectors of the other points in the body generate a circular displacement field around this center of rotation which is identical to what is generated by a pure rotation.
Planar movement of a body is often described using a plane figure moving in a two-dimensional plane. The instant center is the point in the moving plane around which all other points are rotating at a specific instant of time.
The continuous movement of a plane has an instant center for every value of the time parameter. This generates a curve called the moving centrode. The points in the fixed plane corresponding to these instant centers form the fixed centrode.
The generalization of this concept to 3-dimensional space is that of a twist around a screw. The screw has an axis which is a line in 3D space (not necessarily through the origin), the axis of rotation; the screw also has a finite pitch (a fixed translation along its axis corresponding to a rotation about the screw axis).
Pole of a planar displacement
The instant center can be considered the limiting case of the pole of a planar displacement.
The public source identifies “Instant centre of rotation” as in Fig. P is the point of rotation. This brief keeps that definition visible, then builds a research path around Instant, centre and rotation.
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This entry incorporates text from “Instant centre of rotation” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.