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November 15, 2012

# The Spherical Joint

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A spherical joint is similar to a revolute joint in that it only rotates.

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Yet, a spherical joint has three degrees of freedom, rather than only one. Any rotation is possible.

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Hence we cannot compute easily a plane perpendicular to the rotation, and therefore, the planar rotation method is not suitable.

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We can use either Cardan angles or quaternions. Each method requires to represent the correct vector of angles in a different way.

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Hence the bond graph only determines the angular velocities, using a Df element. The Cardan angles or the quaternion vector respectively are integrated from the velocities using special elements.