Mecanism means technology.EncycloClassically, a mechanical means for the conversion of motion, the transmission of power, or the control of these. Mechanisms are at the core of the workings of many machines and mechanical devices. In modern usage, mechanisms are not always limited to mechanical means. In addition to mechanical elements, they may include pneumatic, hydraulic, electrical, and electronic elements. In this article, the discussion of mechanism is limited to its classical meaning. See also Machine.
Most mechanisms consist of combinations of a relatively small number of basic components. Of these, the most important are cams, gears, links, belts, chains, and logical mechanical elements. The last include such devices as ratchets, trips, detents, and interlocks. In order to understand how any mechanism works, their degree of freedom, structure, and kinematics must be considered. See also Belt drive; Cam mechanism; Chain drive; Escapement; Gear; Linkage (mechanism); Ratchet.
Degree of freedom is conveniently illustrated for mechanisms with rigid links. The discussion is limited to mechanisms which obey the general degree-of-freedom equation, where F = degree of freedom of mechanism, l = number of links of mechanism, j = number of joints of mechanism, fi = degree of freedom of relative motion at ith joint, σ = summation symbol (summation over all joints), and λ = mobility number (the most common cases are λ = 3 for plane mechanisms and λ = 6 for spatial mechanisms). See also Degree of freedom (mechanics).
The kinematic structure of a mechanism refers to the identification of the joint connection between its links. Just as chemical compounds can be represented by an abstract formula and electric circuits by schematic diagrams, the kinematic structure of mechanisms can be usefully represented by abstract diagrams. The structure of mechanisms for which each joint connects two links can be represented by a structural diagram, or graph, in which links are denoted by vertices, joints by edges, and in which the edge connection of vertices corresponds to the joint connection of links; edges are labeled according to joint type, and the fixed link is identified as well. Thus the graph of the slider-crank mechanism of illustration a is as shown in illustration b. In this figure the circle around vertex 1 signifies that link 1 is fixed.
a) Mechanism, (b) Graph of mechanism. R = pin joint; P = sliding joint." src="http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE412400FG0010.gif">Slider-crank mechanism, (a) Mechanism, (b) Graph of mechanism. R = pin joint; P = sliding joint.
Kinematics is divided into kinematic analysis (analysis of a mechanism of given dimensions) and synthesis (determination of the proportions of a mechanism for given motion requirements). It includes the investigation of finite as well as infinitesimal displacements, velocities, accelerations and higher accelerations, and curvatures and higher curvatures in plane and three-dimensional motions. See also Kinematics.
The design of mechanisms involves many factors. These include their structure, kinematics, dynamics, stress analysis, materials, lubrication, wear, tolerances, production considerations, control and actuation, vibrations, critical speeds, reliability, costs, and environmental considerations. Modern trends in the design of mechanisms emphasize economical design analysis by means of computer-aided design techniques. See also Computer-aided design and manufacturing.So mecanism is important.
Most mechanisms consist of combinations of a relatively small number of basic components. Of these, the most important are cams, gears, links, belts, chains, and logical mechanical elements. The last include such devices as ratchets, trips, detents, and interlocks. In order to understand how any mechanism works, their degree of freedom, structure, and kinematics must be considered. See also Belt drive; Cam mechanism; Chain drive; Escapement; Gear; Linkage (mechanism); Ratchet.
Degree of freedom is conveniently illustrated for mechanisms with rigid links. The discussion is limited to mechanisms which obey the general degree-of-freedom equation, where F = degree of freedom of mechanism, l = number of links of mechanism, j = number of joints of mechanism, fi = degree of freedom of relative motion at ith joint, σ = summation symbol (summation over all joints), and λ = mobility number (the most common cases are λ = 3 for plane mechanisms and λ = 6 for spatial mechanisms). See also Degree of freedom (mechanics).
The kinematic structure of a mechanism refers to the identification of the joint connection between its links. Just as chemical compounds can be represented by an abstract formula and electric circuits by schematic diagrams, the kinematic structure of mechanisms can be usefully represented by abstract diagrams. The structure of mechanisms for which each joint connects two links can be represented by a structural diagram, or graph, in which links are denoted by vertices, joints by edges, and in which the edge connection of vertices corresponds to the joint connection of links; edges are labeled according to joint type, and the fixed link is identified as well. Thus the graph of the slider-crank mechanism of illustration a is as shown in illustration b. In this figure the circle around vertex 1 signifies that link 1 is fixed.
a) Mechanism, (b) Graph of mechanism. R = pin joint; P = sliding joint." src="http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE412400FG0010.gif">Slider-crank mechanism, (a) Mechanism, (b) Graph of mechanism. R = pin joint; P = sliding joint.
Kinematics is divided into kinematic analysis (analysis of a mechanism of given dimensions) and synthesis (determination of the proportions of a mechanism for given motion requirements). It includes the investigation of finite as well as infinitesimal displacements, velocities, accelerations and higher accelerations, and curvatures and higher curvatures in plane and three-dimensional motions. See also Kinematics.
The design of mechanisms involves many factors. These include their structure, kinematics, dynamics, stress analysis, materials, lubrication, wear, tolerances, production considerations, control and actuation, vibrations, critical speeds, reliability, costs, and environmental considerations. Modern trends in the design of mechanisms emphasize economical design analysis by means of computer-aided design techniques. See also Computer-aided design and manufacturing.So mecanism is important.
