CONVERTIBLE AUTOMOBILE TOP Akmal B. Ismail
Amirrudin B. Mat
Ngu Ya May
Faculty of Mechanical Engineering Kolej Universiti Kejuruteraan & Teknologi Malaysia ABSTRACT
Convertible automobile top mechanism is a mechanism that can open the car roof. The mechanism of convertible automobile top is widely use in automotive fields nowadays. So, here the convertible automobile top and related will be discussed. INTRODUCTION
METHODOLOGY
Nowadays, a convertible automobile top is very popular among consumers. The reason is that they want to be part of the nature while driving and also a convertible automobile top is looks very stylish. So, this project is about to create a convertible automobile top mechanism using all the knowledge learned in Mechanism Design subject.
In order to create the convertible automobile top mechanism, there are several methods that will lead into the fabrication. The methods are shown in the flowchart below:
Start
The convertible automobile top consists of a lot of links that related to each others. In this project, the given convertible automobile top will be redesign according to its requirements. The original design of convertible automobile top cannot move smoothly and met problem during fold back due to the links position and its length. Also, all of the links needs to fit into the predefined space (1.36m x 0.44m) as mentioned. The specified requirements must be met while the employing the given number of links and kinematics pair. Finally, after the redesign process was finished, the model will be fabricated in scale dimension in order to show it is practically function.
Kinematics Diagram
Theoretical Calculation Method
Determination of Position and Length of Links/Elimination
Simulation via Cosmos Motion
Fabrication of Kinematics Model
OBJECTIVES
There are several objectives that need to be achieving in this project which are:
• • •
Product
to create the convertible automobile top mechanism to calculate the position, velocity, and acceleration of the point of interest from the driver link to design the top and rear panel, and all links be able to fold back and fit within the predefined space
Figure 1: Flowchart of Methodology
1
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
i.
Kinematics Diagram
The Piston with length L p will retract and rotates clockwise. As given, the retraction, s = sin (x) ; x = θ p = sin (θ p - ∆θ p ) ,
∆θ p
=change in angle
Step 2: Calculation displacement for Link E which is attached to piston actuator.
Figure 2: Kinematics diagram of convertible automobile top
The Degree of Freedom (DoF) for this kinematics diagram is as below: n = 10 j p = (12 pins + 1slider )
as labeled 1- 10 as labeled A-L
j h = 0
∴ F = 3(10 − 1) − 2(13) − 0 = 27 − 26 =1
h Ef = h Ei – s, h Ef = final length of link E and h Ei =
final length of link E ii.
Theoretical Calculation Method θ E
⎡ h E ⎤ = sin −1 ⎢ ⎥ ⎣⎢ L E ⎦⎥
θ E
⎡h ⎤ = sin −1 ⎢ E ⎥ ⎣ L E ⎦
f
f
Position Analysis
Step 1: Firstly, calculation is started from piston actuator which retraction length is a function of sinusoidal.
i
i
Δθ E = θ E − θ E i
f
Step 3: Calculation angular displacement for Link D which is attach to top panel
L p
θ p
θ A
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
2 3
Rear linkage is assumed has the same amount of angular displacement as link E, then
1 4 10
Δθ D = θ D − θ E = Δθ E f
i
5 9
L R = Length of rear panel Rear linkage is assumed has the same amount of angular displacement as link E, then
6 8 7 2 3 1
Δθ D = θ D − θ E = Δθ E f
i
⎡ L ⎤ = sin −1 ⎢ A sin θ AD ⎥ ⎣ L R ⎦ ⎤ −1 ⎡ L R θ AD = sin ⎢ sin θ D ⎥ ⎣ L A ⎦ ⎡ L ⎤ Δ (θ AD ) = sin −1 ⎢ R sin Δ(θ D )⎥ ⎣ L A ⎦
4 10
θ D
Finally, the position of top panel as the piston actuator retracted is: θ A
= 180° − θ AD − θ D
Velocity Analysis
The velocity analysis here is conducted by using instant center method.
5 9 6 8 7
Possible Instant Center: 1
2
3
4
5
6
7
8
9
12
23
34
45
56
67
78
89
910
13
24
35
46
57
68
79
810
14
25
36
47
58
69
710
15
26
37
48
59
610
16
27
38
49
510
17
28
39
410
18
29
310
19
210
10
110
Acceleration Analysis
There are two methods to be used in acceleration analysis which are determination of acceleration of general point on a floating point and coriolis acceleration.
Total links, n = 10 Total number of instant center n(n − 1)
10(10 − 1)
45
iii.
Determination of Position and Length of Links/Elimination
In order to redesign the convertible automobile
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
2519
iv.
Simulation via Cosmos Motion
2204 1889
To make sure that all of the links that have been modified are reliable, the modified design, the modified design will be tested in Cosmos Motion to see whether the simulation is according to its requirements.
) m m1574 ( t n e m1259 e c a l p 944 s i D
630 315 0
0.00 0.36 0.71 1.07 1.43 1.79 2.14 2.50 2.86 3.21 3.57 3.93 4.29 4.64 5.00 Time (sec)
v.
Fabrication of Kinematics Model
Fabrication is the process after all of the links related are confirmed at the right position and at the right dimension.
Figure 5: Displacement within 10 seconds 368 238 108 ) 2 -22 ^ s / m m-153 (
RESULT AND DISCUSSION
n o i t a r -283 e l e c c A -413
-543
Simulation Result for Convertible Automobile Top:
-674 -804 0 .0 .0 0
Original Design:
0 .3 .3 6
0 .7 .7 1
1 .0 .0 7
1 .4 .4 3
1 .7 .7 9
2 .1 .1 4 2 .5 .5 0 2 .8 .8 6 Time (sec)
3 .2 .2 1
3 .5 .5 7
3 .9 .9 3
4 .2 .2 9
4 .6 .6 4
5 .0 .0 0
Figure 6: Velocity within 10 seconds 482 338 194 51 ) s / m -93 m ( y t i c o -237 l e V
-381 -525 -669 -813
Figure 3: Original Position - SolidWorks Assembly
0 .0 .0 0
0.36
0 .7 .7 1
1 . 07
1 .4 .4 3
1 .7 .7 9
2 .1 .1 4 2 .5 .5 0 2 . 8 6 Time (sec)
3 .2 .2 1
3 .5 .5 7
3 .9 .9 3
4 .2 .2 9
Figure 7: Acceleration within 10 seconds
Cosmos Motion Output (Traced Path, Displacement, Velocity and Acceleration):
Modified Design:
4 .6 .6 4
5 .0 .0 0
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
Cosmos Motion Output (Traced Path, Displacement, Velocity and Acceleration):
273
171 ) 2 ^ s / m 68 m ( n o i t a r e -34 l e c c A
-137
-240 0 .0 .0 0
0 .9 .9 1
1 .8 .8 2
2 .7 .7 3
3 .6 .6 4
4 .5 .5 5 5 .4 .4 5 Time (sec)
6 .3 .3 6
7 .2 .2 7
8 .1 .1 8
9 .0 .0 9 1 0. 0. 00 00
Figure 13: Acceleration within 10 seconds Figure 9: Original Position
Discussion:
Figure 10: Displaced Position - Traced Path 2422
2017
) m m 1612 ( t n e m e c a l p1207 s i D
Figure 14: Original Position Given 802
398 0. 00 00
0 .9 .91
1 .8 .8 2
2. 73 73
3 .6 .6 4
4 .5 5 5 .4 .45 Time (sec)
6 .3 .3 6
7 .2 .27
8 .1 .18
9. 09 09
Figure 11: Displacement within 10 seconds
336.21
183.49 ) c e s 30.77 / m m (
y t i c o -121.94 l e V
-274.66
1 0. 0. 00 00
Original Design of Convertible Automobile Top
As seen from figure 4, there are two tw o arrows (green and red color) which pointed to different direction. These are actually indicating the error during the simulation. simulation. Moreover, there is also fluctuation on the links which making the time cycle of the mechanism cannot be completed. Meanwhile, the links especially link C and top panel also are not fitted within the predefined space – coordinate E (1.36, -0.44).
The world's largest digital library
Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.
Modified Design of Convertible Automobile Top
After several corrections have been done to the original design, those entire links finally can be fitted into predefined space without any error or fluctuation. The time cycle is assigned assigned with 10s, and the mechanism is fully being performed within 10s also. Figure 11, 12, 13 is the displacement, velocity and acceleration graph. All of these graphs are illustrated its smoothness which mean no fluctuation.
Overall, modified design that has been getting through this simulation is the best design. Fabrication for convertible automobile top will be fabricated according to the modified design that performed from the simulation.
CONCLUSION
As the conclusion, the objectives of this project are achieved successfully where all the requirements were obtained. Hopefully, in the future, there is many more research about the convertible automobile top mechanism in order to improve its application.
REFERENCES
[1] Matthew Edward Doyle (1997). The Foundation for CADSPAM: Computer Aided Design of SPAtial Mechanisms. Mechanisms. Master Thesis of Faculty Mechanical Engineering, Virginia Polytechnic Institute and State University. [2] Nilesh and G. K. Ananthasuresh (2002). Contact Aided Compliant Mechanism: Concept and Preliminaries. Preliminaries. Design Engineering Technical Conferences, Montreal,
