Upload
maya-stack
View
232
Download
1
Tags:
Embed Size (px)
Citation preview
Group AChristopher Back
Josephashwin FranklinKwongvoon Wong
Chen Lin
•Windshield Wiper
• Soft Top Mechanism
Cascading Four-bar Mechanisms
•Open Loop Four-bar Configuration- Used in Industrial robots- Usually requires multiple actuators to control motion
•Pantograph Linkage- Originally used in scaled diagrams- Linkages consist of Parallelograms
http://auto.howstuffworks.com/convertible2.htm
Open Loop Four-bar
L= 4, J1= 3, J2= 0 DOF = M =3
Pantograph Linkage
L= 4, J1= 3, J2= 0 DOF = M = 1
Reason for Four-Bar Design Pantograph serves as a locking mechanism Use of Limiting Position simplifies complex
motion Parallel linkages prevent further motion when
collinear
The four-bar linkage has been show as the simplest possible pin-jointed mechanism
Allows for single degree of freedom controlled motion
Grashof Condition
S+L<P+QClass I case:• Ground either link
adjacent to the shortest and you get a crank-rocker
• The shortest link will fully rotate
• the other link pivoted at the ground will oscillate
Tandem system is widely used in the front windshield
One Motor runs both wipers
Parallelogram linkage translates motion to wipers
DOF= 3*(6-1)-2*7=1
Four and Six-bar is a parallelogram linkage.
Duplicate the rotary motion of the driver crank at the driven bar.
Most Common Type of Windshieldmechanism
The coupler of the parallelogram linkage is in curvilinear translation
Remaining at the same angle while all points on it describe identical circular paths
Crank Rocker Input toWindshield Wiper
Varying ???
The slider-crank mechanism Variations of grounding
different links
Inversion D
Window Single Arm
DOF = 3*(4-1)-2*4= 1
We can imagine that the coupler link length is very small
How is the condition when driver link length change?
Diagram of Rear Wiper
Flexblade(TM) Wiper .Its life can extend from months to years
The four-bar linkage mechanism will still be used in this wiper system for a long time
How Windshield Wipers Work. (2006) In: How Stuff Works Available: <http://auto.howstuffworks.com/wiper2.htm> [2007, October 12].
Norton, R.L. Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms and Machines. 3rd ed. New York, McGraw-Hill Co. 2006.
How soft top convertible works. (2006) In: How Stuff Works Available: <http://auto.howstuffworks.com/wiper2.htm> [2007, October 12].
Pantographs.(2006) In: Wikipedia The Free Encyclopedia:
<http://en.wikipedia.org/wiki/Pantograph> [2007, October 12].
• Questions?
The crank-rocker system will change to be two crank system
• Contact points in trains
• Linkages on locomotives
• Pushrods mechanism• Car door linkages
Rear windshield wiper
Single application of
Four-bar mechanism
• Similar to
How is the difference of Rear wiper?