【20160404】Follower Motion Schemes
6 o# T8 @: K' E! z0 p从动件运动模式
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In designing a cam, the objective is to identify a suitable shape for the cam. The primary interest is to ensure that the follower will achieve the desired displacements. The shape of the cam is merely a means to obtain this motion.2 |0 U6 a2 Q( x. g; ^# m8 o
设计凸轮时，我们的目标是找出合适的凸轮外形。但最初的目的是确保从动件将按照预期进行运动。凸轮外形仅仅是获得此种运动的方式。6 E- W9 r4 e- z7 A! S$ \
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Constant Velocity：Uniform velocity, and zero acceleration9 v4 t; R; |: H
常速运动：匀速，加速度为零
# s9 l r6 p' a1 }" p9 Q6 U3 vProblems：The instantaneous jump from one constant value of velocity to another constant value of velocity results in an infinite acceleration.
$ b% @& Z* e$ J; y! X问题：从一种匀速状态到另一状态，所需加速度无限大。: h# n, v; c6 r
constant velocity
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Constant Acceleration：Constant positive and negative accelerations/ m3 w; {, i0 u2 j
匀加速运动：加速度连续同向" l9 a/ S1 Z( T" y* ~+ H
Problems：The abrupt changes of acceleration at the end of the motion result in abrupt changes in inertial forces.
% e1 ~1 X6 i0 U. E8 k8 a1 A% p- A$ m9 ^问题：加速度突然转变，所需内力无限大。4 X' B {" Z1 E7 f ?5 B
constant acceleration
; a6 S& X6 b# |/ S* y8 ?Harmonic Motion：Harmonic motion is derived from trigonometric functions, thus exhibiting very smooth motion curves.
) w" A9 v) K; M3 |; h0 Z简谐运动：三角函数推导而来，因此具有平滑的运动曲线。) F8 G+ y9 b, y$ Q' H. r9 X7 Z
Problems：It has a sudden change of acceleration at the ends of the motion, which can be objectionable at higher speeds.6 s1 `1 v; E8 m5 e' J. j9 o
问题：在运动末尾加速度会突变，这在高速下十分不便。7 ^3 W. {8 J9 `' O% L! P0 W6 h
harmonic motion
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Cycloidal Motion：Cycloidal motion is another motion scheme derived from trigonometric functions.5 G4 X" v3 w3 _9 a, t
摆线运动：另一种由三角函数导出的运动类型。, N5 R2 U, P, q% v& X
This scheme does not have the sudden change in acceleration at the ends of the motion, which makes it popular for high-speed applications." [, i a" J5 F6 W( n4 L7 X
加速度不突变，在高速运动中广为应用。
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cycloidal motion
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The time derivative of the acceleration is referred to as jerk.: a% {7 z. e% i x
加速度对时间的导数称为急动度。
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& O/ T; N+ C# W# XA summary of the peak velocity, peak acceleration, and peak jerk for the different motion schemes, as a function of the rise H and period of the interval T, is shown in Table 9.5.2 @. c( l8 m( }3 P) d: L" y: N
如表所示是各种运动模式的速度峰值、加速度峰值及急动度峰值的对比。
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Table 9.5
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楼主: 黑森林的鹿
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发表于 2016-4-2 19:44:06
楼主
、表示上个学期也是力学拖了大后腿，6级也就是勉强过了，想想自己刷分目标仅是过500，再看看楼主，实在是惭愧。这个学期在搞机械创新，感觉知识实在是不够用，不过也因此更加有兴趣去学专业课，嗯，向楼主学习，据说，不带手机上课就成功了一半呢
