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

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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

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

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Motion of Mechanism

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Dynamic Designer Convertible Animation Variation of design Velocity Analysis and Limit Position Analysis with different R3 link length changing from 30 to 40 units Conclusion With a constant input of theta2, the longer R3 is, the faster angle velocity of R4. That means the soft top can open faster in this condition.

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Dynamic Designer Convertible 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 wont work beyond this limit. For a faster speed of R4,we select R3 a bit longer

11 Variations of the Crank-Rocker in Windshield Wipers Grashof Condition S+L

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

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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

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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

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In above case,R7=0; Design variable:t3,t4,t5,t6,t7

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Two Vector Loop Closure equations R 2 Cos(Ө 2 ) + R 3 Cos(Ө 3 ) + R 4 Cos(Ө 4 ) + R 5 Cos(Ө 5 ) = ACos(Ө A ) R 2 Sin(Ө 2 ) + R 3 Sin(Ө 3 ) + R 4 Sin(Ө 4 ) + R 5 Sin(Ө 5 ) = ASin(Ө A ) R2R2 R3R3 R4R4 R5R5 A

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Two Vector Loop Closure equations R 2 Cos(Ө 2 ) + R 3 Cos(Ө 3 ) + R 6 Cos(Ө 6 ) + R 7 Cos(Ө 7 ) = BCos(Ө B ) R 2 Sin(Ө 2 ) + R 3 Sin(Ө 3 ) + R 6 Sin(Ө 6 ) + R 7 Sin(Ө 7 ) = BSin(Ө B ) R2R2 R3R3 R7R7 B R6R6

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Two Vector Loop Closure equations R 2 Cos(Ө 2 ) + R 3 Cos(Ө 3 ) + R 4 Cos(Ө 4 ) + R 5 Cos(Ө 5 ) = ACos(Ө A ) R 2 Sin(Ө 2 ) + R 3 Sin(Ө 3 ) + R 4 Sin(Ө 4 ) + R 5 Sin(Ө 5 ) = ASin(Ө A ) R 2 Cos(Ө 2 ) + R 3 Cos(Ө 3 ) + R 6 Cos(Ө 6 ) + R 7 Cos(Ө 7 ) = BCos(Ө B ) R 2 Sin(Ө 2 ) + R 3 Sin(Ө 3 ) + R 6 Sin(Ө 6 ) + R 7 Sin(Ө 7 ) = BSin(Ө B ) Ө 4 = Ө o No. EquationsUnknowns Total Unknowns 4 Ө 2 4 Ө 3 (Ө 3, Ө 5, Ө 6, Ө 7 ) Ө 4 or = Ө o Ө 5 Ө 6 Ө 7 0 – 360(deg)

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-Figures show the three angles swept by the windshield wiper for 3 chosen input link lengths

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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)

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How Windshield Wipers Work. (2006) In: How Stuff Works Available: [2007, October 12]. Norton, R.L. Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms and Machines. 3 rd ed. New York, McGraw-Hill Co How soft top convertible works. (2006) In: How Stuff Works Available: [2007, October 12]. Pantographs.(2006) In: Wikipedia The Free Encyclopedia: [2007, October 12].

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