【20160404】Follower Motion Schemes
+ U" B) V7 p* V% L9 G) @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./ f% f6 I1 M& D/ W0 ^2 c z" ^+ r
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。
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Constant Velocity：Uniform velocity, and zero acceleration0 p8 G( w9 a1 ?- |$ {' i
常速运动：匀速，加速度为零, ^+ V7 B3 ]/ C9 \' L$ }- v
Problems：The instantaneous jump from one constant value of velocity to another constant value of velocity results in an infinite acceleration.
8 r! @0 X+ ~! {! i) H% a" o$ X- U1 s问题：从一种匀速状态到另一状态，所需加速度无限大。
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constant velocity
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Constant Acceleration：Constant positive and negative accelerations( Z) X" P u ~5 t( @
匀加速运动：加速度连续同向
3 p( {" J) j9 ~7 w6 O) BProblems：The abrupt changes of acceleration at the end of the motion result in abrupt changes in inertial forces.
; L" ]4 Q5 M/ x0 t* @6 m2 y6 ^问题：加速度突然转变，所需内力无限大。5 c. H; f' n+ v5 }( @ p; _
constant acceleration
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Harmonic Motion：Harmonic motion is derived from trigonometric functions, thus exhibiting very smooth motion curves.
6 F. g+ W5 S* H# z" E, V, G简谐运动：三角函数推导而来，因此具有平滑的运动曲线。; Z# }5 V; Q* i# B
Problems：It has a sudden change of acceleration at the ends of the motion, which can be objectionable at higher speeds.+ c( v* Y5 x0 T; ^% V, e
问题：在运动末尾加速度会突变，这在高速下十分不便。
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harmonic motion
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Cycloidal Motion：Cycloidal motion is another motion scheme derived from trigonometric functions.7 n3 D( W8 X# N3 V* c
摆线运动：另一种由三角函数导出的运动类型。& J2 S" w4 L' r7 {" ~, Z+ j
This scheme does not have the sudden change in acceleration at the ends of the motion, which makes it popular for high-speed applications.; @) e9 A& U: n
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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' q( |7 d+ v0 v7 G; a5 }The time derivative of the acceleration is referred to as jerk.0 |3 K- Y& j" n5 ]$ i1 S
加速度对时间的导数称为急动度。, {0 h# k0 A) d; s: q' s
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A 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.; ]. ] L% F2 g
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
发表于 2016-4-2 19:44:06
、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
