英语翻译 Mechanisms may be categorized in several different ways

英语翻译
Mechanisms may be categorized in several different ways to emphasize their similarities and differences.One such grouping divides mechanisms into planar,spherical,and spatial categories.All three groups have many things in common; the criterion which distinguishes the groups,however is to be found in the characteristics of the motions the links.
A planar mechanism is one in which all particles describe plane curves in space and all these curves lie in parallel planes; i.e.the loci of all points are plane curves parallel to a single common plane.This characteristic makes it possible to represent the locus of any chosen point of a planar mechanism in its true size and shape on a single drawing or figure.The motion transformation of any such mechanism is called coplanar.The plane four-bar linkage,the plate cam and follow,and the slider-crank mechanism are familiar examples of planar mechanism.The vast majority of mechanism in use today is planar.
Planar mechanisms utilizing only lower pairs are called planar linkages; they may include only revolve and prismatic pairs.Although a planar pair might theoretically be included,this would impose no constraint and thus be equivalent to an opening in the kinematics chain.Planar motion also requires that axes of all prismatic pairs and all revolute axes be normal to the plane motion.
A spherical mechanism is one in which each link has some point which remains stationary as the linkage moves and in which the stationary point of all links lie at a common location; i.e.the locus of each point is a curve contained in a spherical surface,and the spherical surface defined by several arbitrarily chosen points are all concentric.The motion of all particles can therefore be completely described by their radial projections,or “shadows”,on the surface of a sphere with properly chosen center.
Spherical linkages are constituted entirely of revolute pairs.A aspheric pair would produce no additional constrains and would thus be equivalent to an opening in the chain,while all other lower pairs have nonspheric motion.In aspheric linkages,the axes of all revolute pairs must intersect at a point.
Spatial mechanisms,on the other hand,include no restrictions on the relative motions of the particles.The motion transformation is not necessary coplanar,nor must it be concentric.A spatial mechanism may have particles with loci if double curvature.Any linkage which contains a screw pair,for example,is a spatial mechanism,since the relative motion within a screw pair is helical.
Spatial mechanisms,on the other hand,include no restrictions on the relative motions of the particles.The motion transformation is not necessary coplanar,nor must it be concentric.A spatial mechanism may have particles with loci if double curvature.Any linkage which contains a screw pair,for example,is a spatial mechanism,since the relative motion within a screw pair is helical.www

“1>机制可以分为以下几种不同的方式强调它们的异同.一个这样的分组分为平面,球面和空间类的机制.所有三组有许多共同的东西,它的标准区分的群体,但要在运动中的链接找到的特点.
一个平面的机制是一个所有平面曲线描述粒子在太空中,所有这些曲线平行的平面上说谎,即所有点位点是平面曲线平行于一个共同的飞机.这一特点使得它可以表示在一个图或数字的任何一个在其真实的大小和形状的平面机构的选定点的轨迹.任何此类机构的运动转换被称为共面.平面四杆机构,凸轮盘和跟进,以及曲柄滑块机构是平面机构熟悉的例子.在目前使用的机制,绝大多数是平面的.
平面机构仅使用较低的被称为平面连杆双,他们可能只包括旋转和棱镜对.虽然理论上平面对可能被包括在内,这会对没有约束,因此相当于一个开放的运动链.平面运动还要求所有棱柱对轴和旋转轴的所有正常的平面运动.
一个球形的机制之一,其中每个环节都有一定的一点,仍然是固定和移动的联系,其中的每个环节都在一个共同的固定点位置的谎言;即每个点的轨迹是一条曲线球载表面,球面任意选择几个点定义都同心.所有粒子的运动,因此可以完整地描述他们的径向预测,或“阴影”对一个球体的表面上,适当选择中心.
球面联系是完全构成转动副.阿非球面对不会产生额外的约束,因此是相当于链中的开放,而所有其他较低对有nonspheric议案.在非球面之间的联系,对所有转动轴必须相交于一个点.