a mechanism for ipad weight scale
TRANSCRIPT
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A MECHANISM FOR IPAD WEIGHT SCALE
ME492 Engineering Project Presentation
DORUK ANGUNDept. Of Mechanical Engineering
Yeditepe University, ISTANBUL
Adviser: Asst. Prof. Namık Cıblak
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Outline
The Need and the Statement of the Problem
The Objective & The Scope Literature Survey Preliminary Design Alternatives Detailed Design Conclusion References
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The Need and the Statement of the Problem
People want IPAD to do multiple tasks.
Weighing an object is a common thing to do.
There is a demand for IPAD weight scale.
Weighing by using the position change of the slider.
Definition of the Need Statement of the Problem
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The Objectives & The Scopes
Low cost Accurate Precise Compact size Ease of
installation Esthetic look
Jewel bearing Registering a
touch Harmless to IPAD Using the screen
as much as possible.
Objectives Scopes
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Literature Survey
Parallelogram Linkage
Consists of two identical cranks fixed with a distance between.
Four straight sides. Opposing sides,
parallel and same length.
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Literature Survey
Slider-Crank Mechanism
Converts rotational motion in to translational motion.
Consists of a rotating driving beam, a connection rod and a sliding body.
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Literature Survey
Capacitive Touchscreen
IPAD 2 has a capacitive touchscreen.
In capacitive touchscreens, there is an insulator such as glass coated with indium tin oxide as conductor.
Touching, distortion in the electrostatic field, determining where the body is touching.
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Preliminary Design Alternatives
Involute MechanismSlider-crank mechanism
with guided stylus
Parallelogram with Slider-crank mechanism
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Mechanism Ideas
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Preliminary Design Alternatives
Battery-Powered Stylus Jointed Stylus Stylus with Wheel
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Stylus Ideas
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Preliminary Design Alternatives
Invo
lute
mec
hani
sm
Slid
er-c
rank
mec
hani
sm w
ith g
uide
d st
ylus
Para
llelo
gram
with
slid
er-c
rank
mec
hani
sm
0
10
20
30
40
50
60
Mechanism
Series1
%
Batte
ry p
ower
ed sty
lus
Join
ted
styl
us
Styl
us w
ith w
heel
0
10
20
30
40
50
60
Stylus (slider)
Series1
%
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Detailed Design
Parallelogram with Slider Crank Mechanism + Stylus With Wheel
+Weight Top part goes downExtension spring extends Slider goes forward
-Weight Extension spring relaxesTop part goes upSlider goes back
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Detailed Design
Analysis
FBD of Crank FBD of Slider FBD of Top
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Detailed Design
Numerical Implementation
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Detailed Design
MATLAB Calculations Inputs“1” represents the weight holder, “2” represents the crank and “3” represents the slider. Masses (kg)
m1=0.137, m2=0.172 , m3=0.086 Link Lengths (m)
r1=0.11, r2=0.15, r3=0.15 Connection points (m)
Length of the spring holder a=0.25*r2,
Distance between spring holder and the top of the link c=0.9*r2 Target mass range (kg)
W∈ [0; 0.427,5] Target θ range (degrees)
θ∈ [75; 15]
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Detailed Design
MATLAB Calculations Outputs
k = 664.2478 N/m L0 = 0.0752 m
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Detailed Design
Mass vs. Theta Slider Position vs. Mass
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Detailed Design
3D Modelling of the Design
7 parts Jewel (pivot hole) Pin Link Spring holders Base Top (weight holder)
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Detailed Design
3D Modelling of the Design
Jewel Bearing
Torus shape hole (bigger diameter)
+
Shaft(smaller diameter)
Minimum fricition, better than other bearings.
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Detailed Design
Manufacturing Process
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Detailed Design
Manufacturing Process
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Detailed Design
k=664.2478 N/m (MATLAB)
L0=0.0752 m (MATLAB) d= 1 mm (design criteria) D=5.85 mm ( ) C= 5.8499 ( )
NOT APPLICABLE (ADJUSTING IS DIFFICULT)
k=35.5 N/m (easy to adjust)
Adjustable hook (adjustable L0)
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Extension Spring Rubber Band
Spring Design
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Detailed Design
Final Design
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Detailed Design
Experimental Results
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Location Location Location Location Location Location Location Location77,5 g 127,5 g 177,5 g 227,5 g 277,5 g 327,5 g 377,5 g 427,5 g
6 43 52 101 125 182 247 3886 42 55 101 122 182 256 3916 42 55 101 125 182 259 3874 41 54 102 129 188 260 4114 41 57 104 125 183 265 4374 42 58 97 125 186 266 4174 42 57 96 125 193 276 4134 42 57 100 126 184 282 4134 40 57 103 129 191 267 4084 42 57 100 127 183 271 418
Mass(g) Location77,5 4,6
127,5 41,7177,5 55,9227,5 100,5277,5 125,8327,5 185,4377,5 264,9427,5 408,3
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Detailed Design
Experimental Results
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y = 3E-06x3 - 0.0044x2 + 2.1309x + 62.128R² = 0.99474
0 50 100 150 200 250 300 350 400 4500
50
100
150
200
250
300
350
400
450
Series1Polynomial (Series1)
Slider Position (pixels)
Mass (
g)
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Detailed Design
Experimental Results
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Position Weight (g) Average (g) Accuracy (%) Accuracy (AVG %) Precision (g)101 235,555403 234,868503 3,540836484 3,238902549 10,727584101 235,555403 234,868503 3,540836484101 235,555403 234,868503 3,540836484102 236,885824 234,868503 4,125636923104 239,525792 234,868503 5,28606241897 230,163719 234,868503 1,17086549596 228,798208 234,868503 0,570640879100 234,218 234,868503 2,952967033103 238,209281 234,868503 4,707376264100 234,218 234,868503 2,952967033
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Conclusion
In this project
A working mechanism for IPAD weight scale is created by Selecting its design among preliminary design ideas. Applying a load analysis by using MATLAB. 3D Modeling and assembling its parts on SOLIDWORKS. Manufacturing its parts. Calibrating it by conducting experiments.
Total Weight =823.71 grams
Dimensions=200mm*150mm*25mm
Capacity= 427,5 grams
Accuracy=+-3.25 grams
Precision= 10.73 grams
Total Cost= 450 TL
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References
[1] Tian, Y., Yao, Y.-A., Wei, X., Joneja, A. “Sliding-crawling parallelogram mechanism” (2014)
[2] H. Jiguang, Z. Chuanyan, Z. Weiyang, “Slider Crank Mechanism Design with Time Ratio and Minimum Transmission Angle” (2014)
[3] G. E. Burnett, D. R. Large, G. Lawson, S. De-Kremer, L. Skrypchuk “A comparison of resistive and capacitive touchscreens for use within vehicles” (2013)
[4] UBC. (n.d.). Stretching of Rubber Bands. Retrieved from http://c21.phas.ubc.ca/sites/default/files/rubber_band_write_up.pdf
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THANK YOU FOR LISTENING
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Appendix
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Appendix
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Appendix
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