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Kinematics of Mechanisms 1Interoduction

Latifah Nurahmi

Latifah.nurahmi@gmail.com

Room C.250

Course outline

Kinematics of Mechanisms by Latifah Nurahmi 2

1• Introduction of kinematics and mechanisms

2• Group presentations

3-5• Position analysis and displacements

6+7• Velocity analysis

8• Mid exam (UTS)

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Course outline

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9+10• Acceleration analysis

11+12• Kinematic Synthesis

13+14• Cam mechanisms and gear mechanisms

15• Lab work – Kinematics of Mechanism

16• Mid exam (UTS)

Introduction

Determine appropriate movement of the

wipers

- View range

- Wipe angle

- Location of pivots

Timing of the wipers

Wiping velocity

The force acting on the machine

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Introduction

Machine

Devices used to alter, transmit, and direct

energy to accomplish a specific objective

Mechanism

Mechanical portion of a machine that

has the function of transferring motion

and forces

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Kinematics

The initial step…

What is the significance of the leg length

that support the platform?

Is it necessary for support legs to cross

and be connected at their midspan?

Or is it better to arrange the so that they

cross closer to the platform?

How far must the cylinder extend to raise

the platform 8 in?

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Dynamics

The second step…

What capacity (maximum force) is

required of the hydraulic cylinder?

Is the platform free of any tendency tip

over?

What cross-sectional size and material

are required of the support legs so they

don’t fail?

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Kinematic analysis and synthesis

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Kinematics : deals with the way things move

Kinematic analysis :

- Determine : position, displacement, rotation, velocity, acceleration

- Provide : geometry, dimension, motion path

Kinematic synthesis :

- Determine : geometry, dimension, operation range

- Provide : motion path, position, velocity

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Terminologies in kinematics

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Degree of freedom

Rotation about an axis

Translation along a direction

In our 3D-space we have

- 3 Rotations

- 3 Translations

X Y

Z

Terminologies in kinematics

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Lower-order joint(contact is surface)

S : Spherical joint

R : Revolute joint

E : Planar joint

P : Prismatic joint

C : Cylindrical joint

H : Helical joint

S

E

C

R

P

H

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Terminologies in kinematics

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Higher-order joint(contact is a point)

Terminologies in kinematics

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Simple link

Rigid body contains only two joints

Crank : a simple link that is able to

complete a full rotation about a fixed

center

Rocker : a simple that oscilates through

an angle

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Terminologies in kinematics

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A link with point of interest

Point of interest : is a point on a

link where the motion is of special

interest

Terminologies in kinematics

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A complex link

A rigid body contains more than

two joints

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Terminologies in kinematics

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The mechanism that works on the plane, generally on the XY-plane.

Mechanism

PlanarMechanism

Spatial Mechanism

The mechanism that works in the space, generally in the XYZ-space.

Terminologies in kinematics

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Planar mechanisms

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Terminologies in kinematics

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Spatial mechanisms

Assignment 1

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A shear press is used to cut and trim electronic circuit board.

Draw the kinematic diagram!

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Assignment 1

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1. Determine which part is fixed, which one is moving

2. Determine the number and type of joints

3. Determine the links

4. Draw the kinematic diagram

fixed

moving

Assignment 1

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Link 1 : fixed part

Link 2: handle

Link 3: Cutting blade

Link 4 : Bar that connects the

cutter and the handle

Point of interest X

Joint A, B, C : Revolute joints

Joint D : Prismatic joint

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Assignment 2

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A linkage is used to operate the water

nozzle at an automatic car wash.

Draw the kinematic diagram.

Find how many joints and links!

Grübler’s equation

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Grübler’s equation

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The degrees of freedom of the following mechanisms can be deduced by Grübler’s equation

Assignment 3

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A beverage can crusher used to reduce the size of cans for easierstorage prior to recycling.

Draw the kinematic diagram!Comput the degree of freedom!

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Assignment 3

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Exercies 3: for next week

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Make a presentation of the following mechanisms, show the video, draw the kinematic diagram,

find its DOF, and mention its applications!

1. Four-bar linkage

2. Five-bar linkage

3. Six-bar linkage

4. Scotch and yoke mechanism

5. Slider crank mechanism

6. Wanzer needle mechanism

7. Stewart-Gough platform

8. Agile eye

9. Cam and follower mechanism