【菜鳥成長記】20歲后，我在機械的每一天

黑森林的鹿

【20160324】Slider-Crank Mechanism
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Another mechanism that is commonly encountered is a slider-crank. This mechanism also consists of a combination offour links, with one being designated as the frame. This mechanism, however, isconnected by three pin joints and one sliding joint. A mechanism that drives a manual water pump is shown in Figure 1.37a. The corresponding kinematic diagram is givenin Figure 1.37b.
  s* U5 F- |! z+ q7 [曲柄滑塊機構也很常見。事實上它也是由4個構件組成，只是其中之一被指定為機架。另外，此機構是以3個轉動副、一個滑動副連接的。圖示為手搖泵及其運動圖示。
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2 k1 p+ e6 ]8 S+ h9 g% G9 \/ MBecause the slider-crank mechanism has one degree of freedom, it is constrained or fully operated with one driver. The pump in Figure 1.37 is activated manually by pushing on the handle (link 3). In general, the pivoted link connected to the frameis called the crank. This link is not always capable of completing a full revolution. The link that translates is calledthe slider. This link is the piston/rod of the pump in Figure1.37. The coupler or connecting rod “couples” the motion of the crank to the slider.
0 N5 C, K8 Q5 [+ B# N4 f因為機構只有一個自由度，因此只需要一個主動力。一般來說曲柄無法完成整周運動。作滑移運動的構件稱滑塊，連接滑塊和曲柄的稱連桿。
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黑森林的鹿

風雪關懷 發表于 2016-3-24 13:13
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黑森林的鹿

【20160325】Position and Displacement Analysis
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/ w6 q" H0 @8 C8 f  ^2 oObjectives：
2 o0 Q' Z% |/ i+ T0 O1. Determine the position of all links in a mechanism as the driver links are displaced.
2. Determine the limiting positions of a mechanism.
目標：
1.在主動件位置已知的情況下確定其余構件的位置；
% H% u! P# F% X8 W, Y4 @2.確定機構的極限位置。

1 J6 x% `$ B* bTwo types of methods

• GraphicalAnalysis
• AnalyticalAnalysis
  

兩種方法：圖示法、解析法

Position and displacement analysis：
6 |# L+ M. b8 J9 t% Z+ ~  Hlocating the position of all links (configuration) in amechanism as the driver link(s) is displaced.
- S1 @5 O) v, l" i; x8 {2 {定義：在主動件位置已知的情況下確定其余構件的位置。
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* i2 G9 l% N- h( i4 ]5 pGraphical Analysis
' E$ `/ l. J) w$ C: b/ f- x/ }圖解法分析步驟
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4 `4 K) B, Y# v1.Point B moves to B’
) }1 A  E8 o+ f2.Point C must always lay on its constrained path
3.The length between B and C must stay constant
畫主動件→畫定軸轉動軌跡→連桿長度不變→交點
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Analytical Analysis
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- Q1 i) S+ j# S- DLimiting position
The configuration of a mechanism that places one of the follower links in an extreme location is called a limiting position.
+ V3 q, K! i. H7 Q7 c6 {從動件之一處于其極限位置的機構位置稱極限位置。

+ s" N% X  y( ?! N0 E4 ?3 g& C1 U. ]# UThe crank and coupler become collinear.
Imbalance angle - the angle between the coupler configuration at the two limiting positions.
曲柄和連桿共線時達到極限位置；
極位夾角：連桿在兩極限位置之間時所形成的角。

* ?, a6 u; o" i" G  z  n0 [& nTransmission Angle
The mechanical advantage ( output force/ input force) is proportional to the sine of the transmission angle.
% W% ?& Y5 [, ~7 N% P3 U傳動角：機械增益（輸出力比輸入力）與傳動角的正弦成正比。

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黑森林的鹿

【20160326】Mechanism design

# `, S3 J; Z* A. J3 \The task of mechanism design: given a desired motion, a mechanism form and dimensions must be determined.
3 a8 [1 d9 }5 s: ^: W: u結構設計：根據運動確定構型。
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& _# ]7 a/ y* KSynthesis: describe the process of designing a mechanism that produces a desired output motion for a given input motion.
6 @# \1 }7 [+ q, w構型綜合：描述給定輸入運動實現輸出運動的機構設計過程。
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分類：
Type synthesis: selecting a mechanism type
4 S( r2 R2 R' |" v& ADimensional synthesis: determining the link lengths
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Time Ratio
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Kinematically balanced mechanisms：the motion characteristics of the outward stroke are identical to those of the inward stroke.
1 g8 j& k: u7 o) q% {6 v運動對稱機構：內外沖程等時。
Quick-return mechanisms：difference in the speed of the forward and return strokes.
急回機構：沖程不等時。

Working stroke: smoothing the surfaces of metal. ( slower) 工作沖程
3 w+ \0 f7 K. ]0 wReturn stroke:nothing to do. ( quicker) 急回沖程

. Q9 I% F/ _& {, DTime ratio: a measure of the quick return action of a mechanism
' V- R, b' Q, e6 O! E9 z時間比：用于度量急回機構
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黑森林的鹿

【20160327】Design of Slider-Crank Mechanisms
* f7 Q% _/ o& f" G+ O! n! Y: w曲柄滑塊機構設計
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7 H6 o. l5 J1 T7 _In-line slider-crank mechanism: has the crank pivot coincident with the axis of the sliding motion of piston pin.
曲柄軸心與滑塊運動軌跡共線。

In-line slider-crank mechanism produces balanced motion.
* M; j& @" B: f. X) i. [3 S該機構產生平衡運動。
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Offset slider-crank mechanism: has the crank pivot not coincident with the axis of the sliding motion of pin.
% h5 t. G$ w; @& o3 M曲柄軸心與滑塊運動軌跡不共線。

Determining an appropriate offset distance, L1, and the two links lengths, L2 and L3, to achieve the desired stroke, |ΔR4|max, and imbalance angle.
, }' t8 K9 C$ k' b9 D確定補償距離及構件桿長以獲得需要的沖程、極位夾角。
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Questions
- g; T' L* ~# R) M6 }' WThe stroke, |ΔR4|max, and imbalance angle are given, determining an appropriate offset distance, L1, and the two links lengths, L2and L3.
% K1 L0 j9 M, {) L常見題型，給定沖程、極位夾角，確定補償距離及構件桿長。

解題公式：
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黑森林的鹿

【20160328】Design of Crank –Rocker Mechanisms
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The design of a crank-rocker mechanism-determining appropriate lengths of all four links to achieve the desired throw angle, (Δθ4)max, and imbalance angle, β.
7 Z0 }1 Y* U0 \( s曲柄連桿機構設計：給定極位夾角求四桿長度。

: Y8 l2 C% O5 ~, `- jQuestions:
9 B' o7 q- G7 O* o8 x0 LThe desired throw angle, (Δθ4)max, and imbalance angle, β are given.
Determining appropriate lengths of all four links.
2 U# i( ?6 {1 b5 z6 n( _+ w典型問題：
給定極位夾角求四桿長度。
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計算公式：

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