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# Application of Four-Bar Mechanisms in Cars

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1. Application of Four-Bar Mechanisms in Cars Group A Christopher Back Joseph Ashwin Franklin Kwongvoon Wong Chen Lin • Windshield Wiper • Soft Top Mechanism

2. Components of 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

3. Kinematic Diagram • Open Loop Four-bar • L= 4, J1= 3, J2= 0 • DOF = M =3 • Pantograph Linkage • L= 4, J1= 3, J2= 0 • DOF = M = 1

4. Motion of Mechanism http://auto.howstuffworks.com/convertible2.htm

5. Motion of Mechanism

6. Position and Velocity analysis when R3= 30 in.

7. Position and Velocity analysis when R3= 35 in.

8. Position and Velocity analysis when R3= 40 in.

9. Dynamic DesignerConvertible Animation

10. Dynamic DesignerConvertible Animation • The proceeding figures shows ,when the R3 is longer, it has a smaller rotation range of output link R4. • That means : • For wider rotation angle of R4,we select R3 a bit shorter • Theta4 has the angle limit from 0 to Pi. It won’t work beyond this limit. • For a faster speed of R4,we select R3 a bit longer

11. Variations of the Crank-Rockerin Windshield Wipers Grashof Condition S+L<P+Q Class 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

12. Tandem system Tandem system is widely used in the front windshield One Motor runs both wipers Parallelogram linkage translates motion to wipers

13. 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 Windshield Mechanism

14. 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 to Windshield Wiper

15. Two Vector Loop Closure equations • In above case,R7=0; • Design variable:t3,t4,t5,t6,t7

16. Two Vector Loop Closure equations R5 R4 A R3 R2 R2Cos(Ө2) + R3Cos(Ө3) + R4Cos(Ө4) + R5Cos(Ө5) = ACos(ӨA) R2Sin(Ө2) + R3Sin(Ө3) + R4Sin(Ө4) + R5Sin(Ө5) = ASin(ӨA)

17. Two Vector Loop Closure equations R7 B R3 R6 R2 R2Cos(Ө2) + R3Cos(Ө3) + R6Cos(Ө6) + R7Cos(Ө7) = BCos(ӨB) R2Sin(Ө2) + R3Sin(Ө3) + R6Sin(Ө6) + R7Sin(Ө7) = BSin(ӨB)

18. Two Vector Loop Closure equations R2Cos(Ө2) + R3Cos(Ө3) + R4Cos(Ө4) + R5Cos(Ө5) = ACos(ӨA) R2Sin(Ө2) + R3Sin(Ө3) + R4Sin(Ө4) + R5Sin(Ө5) = ASin(ӨA) R2Cos(Ө2) + R3Cos(Ө3) + R6Cos(Ө6) + R7Cos(Ө7) = BCos(ӨB) R2Sin(Ө2) + R3Sin(Ө3) + R6Sin(Ө6) + R7Sin(Ө7) = BSin(ӨB) Ө4 = Ө6 +180o No. EquationsUnknowns Total Unknowns 4 Ө2 4 Ө3 (Ө3, Ө5, Ө6, Ө7) Ө4or = Ө6 +180o Ө5 Ө6 Ө7 0 – 360(deg)

19. Windshield Wiper Animation

20. Wiper Angle Sweep -Figures show the three angles swept by the windshield wiper for 3 chosen input link lengths

21. Analysis of Windshield Wiper

22. The Four-bar linkage mechanism will still be used in this wiper system for a long time It advantage includes Utilize one motor to drive two wiper blade Parametric changes gives different arc Input link can be place in various location ONE disadvantage commonly reported is Joint failure (joint dislocation) Conclusions

23. References • 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].

24. Questions?