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Overconstrained mechanism
Moveable linkage with zero mobility / From Wikipedia, the free encyclopedia
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In mechanical engineering, an overconstrained mechanism is a linkage that has more degrees of freedom than is predicted by the mobility formula. The mobility formula evaluates the degree of freedom of a system of rigid bodies that results when constraints are imposed in the form of joints between the links.
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If the links of the system move in three-dimensional space, then the mobility formula is
where N is the number of links in the system, j is the number of joints, and fi is the degree of freedom of the ith joint.
If the links in the system move planes parallel to a fixed plane, or in concentric spheres about a fixed point, then the mobility formula is
If a system of links and joints has mobility M = 0 or less, yet still moves, then it is called an overconstrained mechanism.