【20160404】Follower Motion Schemes) R5 B3 |' t. I# n0 y
从动件运动模式
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9 ]; ]4 A+ k; u, q5 _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. D/ U' K4 [3 L5 j* m/ U0 \+ f
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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+ p$ \4 f/ H. t; p- `# X5 DConstant Velocity：Uniform velocity, and zero acceleration
" K j5 R2 x6 A" E2 u常速运动：匀速，加速度为零0 R9 K- @7 F C' F5 e7 A
Problems：The instantaneous jump from one constant value of velocity to another constant value of velocity results in an infinite acceleration.% P" V1 t* z0 \# {! h/ a9 Q6 [" }; Q
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
/ E c+ P# I+ |1 KConstant Acceleration：Constant positive and negative accelerations
4 c! i: ?; U. N/ R匀加速运动：加速度连续同向
# M" j- W" R* e6 I5 g6 ], n2 `Problems：The abrupt changes of acceleration at the end of the motion result in abrupt changes in inertial forces.
) h! l4 L7 W1 Z* E: e' q问题：加速度突然转变，所需内力无限大。
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constant acceleration
_1 Q K( W4 \9 FHarmonic Motion：Harmonic motion is derived from trigonometric functions, thus exhibiting very smooth motion curves.1 J* c( X! d' S' B$ P
简谐运动：三角函数推导而来，因此具有平滑的运动曲线。
/ G- m$ m; _: m3 @- E/ AProblems：It has a sudden change of acceleration at the ends of the motion, which can be objectionable at higher speeds.: G3 E1 V4 w* u- s4 Z/ L: _
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
& W/ ]: L# q! e; B8 jCycloidal Motion：Cycloidal motion is another motion scheme derived from trigonometric functions.7 e' H0 L0 \8 B: l3 }
摆线运动：另一种由三角函数导出的运动类型。1 k: M0 E$ H" W' t7 {
This scheme does not have the sudden change in acceleration at the ends of the motion, which makes it popular for high-speed applications.
; C# j9 Q6 r7 Z% G' Z [. 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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B: u8 Z" B6 S" b. Z! r E3 M0 r- |The time derivative of the acceleration is referred to as jerk.
4 Q0 p3 M) h- E加速度对时间的导数称为急动度。' f, Q7 F* C0 H {
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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.
$ h% R7 d8 Z" R+ ]* o6 D7 p3 X9 E; p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
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、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
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