1、Theory of Machines and Mechanisms(機(jī)械原理)Chapter1 IntroductionChapter2 Structural Analysis of Planar MechanismsChapter3 Kinematic Analysis of MechanismsChapter4 Planar Linkage MechanismsChapter 5 Cam MechanismsChapter 6 Gear MechanismsChapter 7 Gear TrainsChapter 8 Other Mechanisms in Common UseChapte

2、r 9 Balancing of MachineryChapter 10 Motion of Mechanical Systems and Its RegulationChapter 11 Efficiency of MachineChapter 3Kinematic Analysis of Mechanisms本章重點(diǎn)： 平面機(jī)構(gòu)速度和加速度分析的圖解法 （包括基點(diǎn)法和重合點(diǎn)法）。本章難點(diǎn)： 重合點(diǎn)法中哥氏加速度的正確確定。3.1 Tasks and Methods of Kinematic Analysis3.2 Velocity Analysis by the Method of ins

3、tant Centres3.1 Tasks and Methods of Kinematic Analysis不考慮引起機(jī)構(gòu)運(yùn)動(dòng)外力的影響，僅僅研究已知原動(dòng)件運(yùn)動(dòng)規(guī)律的條件下，輸出構(gòu)件的運(yùn)動(dòng)情況.Task: to find positions, velocities and accelerations or angular positions, angular velocities and angular accelerationsPosition: to determine whether all links will interfere(干涉) with each other,to fin

4、d locus(軌跡)Velocity: to calculate the stored kinetic energy(動(dòng)能) or power(功率) P. Acc.：To calculate the dynamic forcesmethod graphical method (圖解法): 直觀，精度不高 analytical method (解析法) : 精度高，計(jì)算煩瑣 experimental method (實(shí)驗(yàn)法) : 需專(zhuān)門(mén)的儀器 Instant(瞬時(shí)的) centre method for velocityVector(矢量) equation method3.2 Veloci

5、ty Analysis by the Method of instant Centres3.2.1 Definition of the Instant Centre 剛體2相對(duì)于另一剛體1（固體坐標(biāo)系）作平面運(yùn)動(dòng)，在任一瞬時(shí)，該平面運(yùn)動(dòng)都可看成繞某一相對(duì)靜止點(diǎn)的轉(zhuǎn)動(dòng)，該點(diǎn)稱(chēng)為速度瞬時(shí)中心（瞬心） instant centerP12 VA2A1剛體2上的A點(diǎn)相對(duì)于剛體1上的A點(diǎn)的相對(duì)速度， VA2A1AP.VB2B1同理。 Suppose that the positions of points A and B, the directions of VA2A1 and VB2B1 are kno

6、wn.可通過(guò)VA2A1，VB2B1求P12點(diǎn)。 VA2A1AP. VB2B1BP. instant centerP12 One of bodies is staticabsolute instant center Both of them are movingrelative instant centerAttention:a pair of coincident(重合) points, the absolute(絕對(duì)) velocities of which are the same, in both magnitude(大小) and direction.具有相同的絕對(duì)速度的重合點(diǎn) 。 i

7、nstant centerrelative velocity is zero.兩構(gòu)件上相對(duì)速度是零的重合點(diǎn)3.2.2 Number of Instant Centers of a Mechanism發(fā)生相對(duì)運(yùn)動(dòng)的任意兩構(gòu)件之間都有一個(gè)瞬心 knumber of links including the frameinstant centerthe center of revolutes3.2.3 Location of the Instant Center of two links connected by a kinematic pair(1) Revolute Pair若兩構(gòu)件組成回轉(zhuǎn)副，則

8、回轉(zhuǎn)副中心為其速度瞬心；(2) Sliding Pair Instant center:lies at infinity in either directionPerpendicular to the guide-way. Attention：The common normal(公法線(xiàn)) may pass through any point !(3) Higher Pair:Pure-rolling PairInstant centerthe point of contact (4)Higher Pair :rolling & sliding PairInstant centerlies so

9、mewhere on the common normal（公法線(xiàn)） through the point of contact3.2.4 Theorem of Three Centres (Aronhold-Kennedy Theorem)Any three links have three instant centers.They must lie on a straight line CVc 2Vc 3P12P13AB123233.2.5 Applications of Instant CentersExample1: Locate all instant centers for the r

10、evolute four-bar linkage. (1) locate all instant centers for the mechanism(2) find the ratio 2/4Find：P12、P23、P34和P14；Solution：再由三心定理可知：(1) locate all instant centers P12 ， P14P24P23 ， P34P12 ， P23P13P14 ， P34(2) find the ratio 2/4P24在P12、P14的同一側(cè)，2和4方向相同。P24在P12、P14之間，2和4方向相反。P24為構(gòu)件2和構(gòu)件4的速度瞬心，兩構(gòu)件在P24

11、處應(yīng)有相等的絕對(duì)速度，即:Example2:For the following Slider-Crank Mechanism，Given: lAB, lBC,，1 locate all instant centers for the mechanism ；the velocity of follower link3 V3 。Solution：(1) Find Instant centerP13(2) Determine V3Example3In the cam mechanism as shown in the following fig. the cam2 rotates anti-cloc

12、kwise at a constant speed ，Determine the velocity of the follower2 for the position shown. (1) Find Instant center P23P23應(yīng)在P12 ， P13的連線(xiàn)上P23P23 在接觸點(diǎn)的公法線(xiàn)上(2) Determine V3Solution：3.2.6 Advantages and Disadvantages of the Method of Instant CentersExcellent tool in simple mechanisms. difficult to find Instant Center in a complex mechanismit can not be used in acceleration analysis.Attentions (this chapter