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A four-bar linkage, also called a four-bar, is the simplest movable closed chain linkage. It consists of four bodies, called bars or links, connected in a loop by four joints. Generally, the joints are configured so the links move in parallel planes, and the assembly is called a ''planar four-bar linkage''.〔Hartenberg, R.S. & J. Denavit (1964) (Kinematic synthesis of linkages ), New York: McGraw-Hill, online link from Cornell University.〕 If the linkage has four hinged joints with axes angled to intersect in a single point, then the links move on concentric spheres and the assembly is called a ''spherical four-bar linkage''. ''Bennett's linkage'' is a spatial four-bar linkage with hinged joints that have their axes angled in a particular way that makes the system movable.〔Hunt, K. H., Kinematic Geometry of Mechanisms, Oxford Engineering Science Series, 1979〕〔( J. M. McCarthy and G. S. Soh, Geometric Design of Linkages, 2nd Edition, Springer 2010 )〕 ==Planar four-bar linkage== thumb Planar four-bar linkages are constructed from four links connected in a loop by four one degree of freedom joints. A joint may be either a ''revolute'', that is a hinged joint, denoted by R, or a prismatic, as sliding joint, denoted by P. A link connected to ground by a hinged joint is usually called a crank. A link connected to ground by a prismatic joint is called a slider. Sliders are sometimes considered to be cranks that have a hinged pivot at an extremely long distance away perpendicular to the travel of the slider. The link that connects two cranks is called a ''floating link'' or ''coupler.'' A coupler that connects a crank and a slider, it is often called a ''connecting rod.'' There are three basic types of planar four-bar linkage depending on the use of revolute or prismatic joints: :1. Four revolute joints: The planar quadrilateral linkage is formed by four links and four revolute joints, denoted RRRR. It consists of two cranks connected by a coupler. :2. Three revolute joints and a prismatic joint: The slider-crank linkage is constructed from four links connected by three revolute and one prismatic joint, or RRRP. It can be constructed with crank and a slider connected by the connecting rod. Or it can be constructed as a two cranks with the slider acting as the coupler, known as an ''inverted slider-crank.'' :3. Two revolute joints and two prismatic joints: The double slider is a PRRP linkage.〔 This linkage is constructed by connecting two sliders with a coupler link. If the directions of movement of the two sliders are perpendicular then the trajectories of the points in the coupler are ellipses and the linkage is known as an ''elliptical trammel'', or the Trammel of Archimedes. Planar four-bar linkages are important mechanisms found in machines. The kinematics and dynamics of planar four-bar linkages are important topics in mechanical engineering. Planar four-bar linkages can be designed to guide a wide variety of movements. 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「Four-bar linkage」の詳細全文を読む スポンサード リンク
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