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Alpha[bnum] returns the angular acceleration (2D) or angular acceleration vector (3D) of body bnum.

• In Modeler2D, Alpha returns a scalar Alpha.
• In Modeler3D, Alpha returns the angular acceleration vector of the form: {Alphax, Alphay, Alphaz}.
• If the
Euler solution method is specified with SetSymbols, Alpha returns the angular acceleration in terms of Euler parameters and their second derivatives. With the Angular solution method Alpha simply returns CapitalThetabnumdd (2D) or {CapitalOmegaxbnumd, CapitalOmegaybnumd, CapitalOmegazbnumd} (3D).
• In Modeler3D, Alpha accepts the Coordinates option to specify whether the angular acceleration should be returned in Global or body Local coordinates. The default setting is Coordinates->Global.
• See also: Acceleration, Omega, Rotation.

Further Examples

Load the Modeler3D package and define a simple model.

Here is the angular acceleration of the link body, expressed in terms of Euler parameters.

If we rebuild the model in terms of angular coordinates, the symbolic results differ but the numeric results are unchanged.

Compare the results from the same inputs. The symbolic expression for the angular acceleration is trivial because the modeling coordinate system used here is global angular coordinates.

The angular acceleration expressed in the local coordinate system of the link body is almost numerically identical because the link body is almost aligned with the global coordinate system.

See HelpModel3D.