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기구학 기본개념
Chap 2. Kinematics Fundamentals
Micro-Electro-Mechanical Systems (MEMS) is the technology of the future, allowing
microscopic devices to replicate the functionality of current large-scale systems, or
even perform tasks previously unimaginable.
MEMS are either used as sensors or actuators, possibly operating in a wide range of
physical domains spanning electrostatics, mechanics, piezo-electrics, thermodynamics,
electromagnetics, fluidics, and optics. In all of these cases, they must be
accompanied by electronic circuitry for control and/or monitoring.
(Excerpted from the textbook)
기구학 기본개념
2.6 기구와 구조 (Mechanisms and Structures)
DOF=3(4-1)-2(4)=1 DOF=3(3-1)-2(3)=0 DOF=3(2-1)-2(2)=-1
• 기구 (Mechanism) • 구조 (Structures)
(Excerpted from the textbook)
기구학 기본개념
2.8 모순 (Paradox)
DOF=3(5-1)-2(6)=0
DOF=0 (?)1
X
DOF=3(4-1)-2(4)=1
L =5
J1=6
(Excerpted from the textbook)
기구학 기본개념
2.8 모순 (Paradox)
1
23
1 2
3
DOF=3(3-1)-2(3)=0X
DOF=1
고정링크 길이 = 링크 2 길이 + 링크 3 길이
Kutzbach 공식은 링크의 크기, 모양을 고려하지 않았기 때문에
링크 형상이 독특한 경우에는 틀릴 수 있다.
(Excerpted from the textbook)
기구학 기본개념
2.10 링크 변환 (Linkage Transformation)
• 링크/조인트 특성 변화
• 입/출력 운동 유사
• 자유도 변화 없음.
(Excerpted from the textbook)
기구학 기본개념
2.10 링크 변환 (Linkage Transformation)
길이 변화
L =3
J1=2
J2=1
DOF=3(3-1)-2(2)-(1)=1
(Excerpted from the textbook)
기구학 기본개념
2.12 전이 (Inversion)
• 4절 기구 (Four-bar linkage)
Crank-rocker
Double-crankDouble-rocker
완전 회전 Crank
Rocker
O
X
(Excerpted from the textbook)
기구학 기본개념
2.13 Grashof 조건
• 4절 기구의 전이에 따른 회전운동의 형태를 링크 길이만으로 판단할 수
있는 관계식.
(Relationship which predicts the rotational behavior of a four-bar
linkage’s inversions based only on the link length.)
만족Grashof 기구
만족XNon-Grashof 기구
최소한 1개 링크는 완전 회전 가능.
어느 링크도 완전 회전 불가능.
크랭크(crank)
로커(rocker)
최단링크길이 최장
링크길이
나머지두링크길이
<_S + L P + Q(?)
기구학 기본개념
Grashof 기구
Non-Grashof 기구
Class I
(S+L < P+Q)
Double-Crank GCCC
Crank-Rocker
(L1=s)
GCRR (L2=s)
Double-Rocker GRCR (L3=s)
Rocker-Crank GRRC (L4=s)
Class II
(S+L > P+Q)
(L1=L)
(L2=L)
(L3=L)
(L4=L)
4절 기구
Class III
(S+L = P+Q)
SC Double-Crank SCCC
SC Crank-Rocker
(L1=s)
SCRR (L2=s)
SC Double-Rocker SRCR (L3=s)
SC Rocker-Crank SRRC (L4=s)
Deltoid S2X Two pairs
Square S3X All same
Triple-Rocker RRR1
Triple-Rocker RRR2
Triple-Rocker RRR3
Triple-Rocker RRR4
1
2 3
4
G : groundC : crankR : rocker
2.13 Grashof 조건
기구학 기본개념
2.16 Compliant mechanisms
• 가위
No joint
No friction (마찰)
No wear (마모)
No lubrication (윤활)
No cooling (냉각)
No assembly (조립)
Better precision (정밀도)
기구학 기본개념
2.16 Compliant mechanismsCompliance is the opposite of stiffness. A link that is compliant is capable
of significant deflection in response to load. A typical example is a switch.
Certain thermoplastics allow thin sections to be flexed repeatedly without
failure. 열가소성 수지(플라스틱)
(Excerpted from the textbook)
기구학 기본개념
2.16 Compliant mechanisms
• 가위 No joint
No friction (마찰)
No wear (마모)
No lubrication (윤활)
No cooling (냉각)
No assembly (조립)
Better precision (정밀도)
(Excerpted from the textbook)
기구학 기본개념
2.16 Compliant mechanismsIn MEMS, due to an increase in surface to volume ratio, the frictional
forces dominate. Therefore a MEMS mechanism must avoid joints. Due to
the limitations of microfabrication methods, MEMS structures have to be
monolithic and assembly must be avoided. Compliant mechanisms provide
a jointless alternative to conventional rigid body mechanisms.
(Excerpted from the textbook)