清华大学：《机械原理》课程PPT教学课件（双语版）Chap 2 Kinematics fundamental

chap 2 Kinematics fundamental ■2.1 Basic concept 2.2 Determining Degree of Freedom 2,3 How does a kinematic chains transform into a mechanism? 2.4 Kinematic Diagram of Mechanism 2.5 Principle of Mechanism Constitution

Chap.2 Kinematics fundamental ◼ 2.1 Basic Concept ◼ 2.2 Determining Degree of Freedom ◼ 2.3 How does a kinematic chains transform into a mechanism? ◼ 2.4 Kinematic Diagram of Mechanism ◼ 2.5 Principle of Mechanism Constitution

2.1 Basic Concepts of Mechanisms Degree of freedom(自由度 Link(构件) Kinematic pairs( Joints)(运动副) Machine element(机械零件) Fixed link〔 frame)(机架) Crank, couple, rocker(曲柄、连杆、摇杆 Kinematic chain(运动链) Mechanism(机构) Machine(机器)

2.1 Basic Concepts of Mechanisms Degree of freedom (自由度) Link （构件） Kinematic Pairs (Joints)（运动副） Machine Element（机械零件） Fixed link ( frame)（机架） Crank, couple,rocker（曲柄、连杆、摇杆） Kinematic Chain（运动链） Mechanism（机构） Machine（机器）

2.1Basic Concepts of Mechanisms(1) Degree of Freedon(自由度) The system's DOF is equal to the number of independent parameters which are needed to uniquely define its position in space at any instant of time

Degree of Freedom（自由度） The system’s DOF is equal to the number of independent parameters which are needed to uniquely define its position in space at any instant of time. 2.1Basic Concepts of Mechanisms(1)

2.1Basic Concepts of Mechanisms(2) ink(构件) is a rigid body which possesses at lease two nodes which are points for attachment to other links Ternary link nodes nodes Binary link Quaternary link

Link（构件）:is a rigid body which possesses at lease two nodes which are points for attachment to other links. nodes Ternary link Binary link Quaternary link nodes 2.1Basic Concepts of Mechanisms(2)

2.1Basic Concepts of Mechanisms3) Joint(铰链或运动副) Joint: is a connection between two or more links(at their nodes), which allows some motion, or potential motion, between the connected links Joints also called kinematic pairs) can be classified in several ways By the type of contact between the elements, line, point, or surface 2. By the number of degree of freedom allowed at the joint 3. others

Joint: is a connection between two or more links(at their nodes), which allows some motion, or potential motion, between the connected links. Joints (also called kinematic pairs) can be classified in several ways: 1. By the type of contact between the elements, line, point, or surface. 2. By the number of degree of freedom allowed at the joint. 3. Others 2.1Basic Concepts of Mechanisms(3) Joint (铰链或运动副)

2.1Basic Concepts of Mechanisms(4) Lower pairs(低副) joints with surface contact Prismatic joint Revolute joint Cylindric joint Spherical joint Helical joint Planar joint ype joint R joint C joint S ioint f joint DOF

Lower pairs（低副）:joints with surface contact Prismatic joint Revolute joint Cylindric joint Spherical joint Helical joint Planar joint Type P joint R joint C joint S joint H joint F joint DOF 1 1 2 3 1 3 2.1Basic Concepts of Mechanisms(4)

2.1 Basic Concepts of mechanisms( (5) Higher pairs(高副): joints with point or line contact DOF 5

Higher pairs（高副）:joints with point or line contact 2.1Basic Concepts of Mechanisms(5) DOF 5 2

2.1 Basic Concepts of Mechanisms(6) Examples of higher pairs 烈Z Form -closed Force-closed closed by its geometry need external force

Examples of higher pairs Force –closed need external force Form –closed closed by its geometry 2.1Basic Concepts of Mechanisms(6)

2.1 Basic Concepts of Mechanisms(7) iagram of Kinematic pairs(运动副简图) Prismatic joint Revolute joint Cylindric joint Spherical joint Helical joint Diagram Joint R joint Joint S ioint H ioint DOF

Diagram of Kinematic pairs（运动副简图） Prismatic joint Revolute joint Cylindric joint Spherical joint Helical joint Type P joint R joint C joint S joint H joint DOF 1 1 2 3 1 Diagram 2.1Basic Concepts of Mechanisms(7)

2.1 Basic Concepts of Mechanisms(8) Machine element(机械零件): minimum unit during manufacturing This link has several machine elements B Inar link

Machine Element（机械零件）: minimum unit during manufacturing 2.1Basic Concepts of Mechanisms(8) Binary link This link has several machine elements