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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 connecting the links. 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''. == Sarrus linkage == A well-known example of an overconstrained mechanism is the Sarrus mechanism, which consists of six bars connected by six hinged joints. A general spatial linkage formed from six links and six hinged joints has mobility : and is therefore a structure. The Sarrus mechanism has mobility M=1, rather than M=0, which means it has a particular set of dimensions that allow movement.〔K. J. Waldron, ''Overconstrained Linkage Geometry by Solution of Closure Equations---Part 1. Method of Study,'' Mechanism and Machine Theory, Vol. 8, pp. 94-104, 1973.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Overconstrained mechanism」の詳細全文を読む スポンサード リンク
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