ME4053 Oral and Visual Presentations

1
ME4053 Oral and Visual Presentations
Dr. Ferri, Section A-3 Date
Always place section on your Notebook,
Abstracts, And Presentations

• Outline
• Slide composition
• Use of equations
• Figures
• Plots

2
Introduction

• Objective
• Investigate the vibration characteristics of a
• 2-DOF system with a passive vibration absorber.
• Specific Characteristics
• Determine the 1-DOF natural frequency
• Use an absorber to minimize the beam vibration at
  a specified frequency
• Measure the displacement-force transfer function
• Determine the mode shapes

List specific tasks- avoid saying To understand
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Apparatus and Setup
Accelerometer
Absorber
Anchor
Main Beam
Absorber Beam
Shaker
Function Generator
Amp for Accelerometer
Amp for Force Transducer
Oscilloscope
Note Sketch of experimental setup does not need
to be fancy. This one is fine.
4
Setup
Actual Student Work!
This is not fancy enough! There is a missing
amplifier, and the connections are not clear.
5
Apparatus and Setup
Power Supply
Analog Output
Ch 1
Ch 2
Computer
Encoder
Data Acquisition Board
Flywheel
Optical Encoder
Motor
Actual Student Work!
Use light or white backgrounds, or use
light-colored lettering/lines on dark background
6
Experimental Setup
Dont cross lines!
Oscilloscope
Arrow does not point to transducer
Ch 1 Ch 2
Force Transducer
Power Supply
Power Supply
Accelerometer
Magnetic Mass
Main Beam
Absorber Beam
Clamp
Function Generator
Harmonic Signal
Shaker
Use arrows to show signal flow
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Example of a Bad Slide
A bad slide is one in which you attempt to write
every word and every point that you want to
make. While everyone in the room goes to sleep,
you drone on, and on, and on, etc. Worse yet, you
dont even make eye contact with the audience
because your eyes are directed towards the
screen, making sure that you dont miss a single
word. Keep the amount of text on your slides
within reason. There are times when a lot of
words are necessary this is not one of them.
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Choose the right font
24 point Arial is good for titles and major
headings
18 point Arial is also good, especially when its
bold and in color
16 point is adequate for the fine details, but I
wouldnt recommend going any smaller (like 14
point) or even smaller (like 12 point)
Avoid weird fonts as they can distract the
audiences attention away from your main points!
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Absorber Procedure

• The absorber mass was adjusted for minimum
  displacement response at assigned frequency, fd
  30 Hz.
• At different frequencies, the output from the
  accelerometer and the time delay between input
  and output waves were recorded.

10
Motor Parameter Data Collection Procedure

• Opened WINCON and started SIMULINK
• Opened Control Template 1
• Specified vin
• Built model
• Set up a plot for the data
• Ran simulation and saved as an M-file
• Same procedure repeated for vin 0.8, 0.9, 1.0,
  1.1, and 1.2

Why does the audience need to know this?

• This slide has two problems
• It is way too specific and should be more
• conceptual.
• 2. The font is too small

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Experimental Procedure I

• Measured temperature and diameter of the speaker
  baffle
• Set oscilloscope to average and gate (reduce
  noise effect)
• Generate five 5 kHz sinusiodal bursts 100 ms long
• Microphone placed at 2 cm from speaker baffle
• Time delay and RMS voltage of microphone recorded
• Repeated every 2 cm up to 40 cm
• Sample waveform obtained for input signal and
  microphone output (_at_ 20 cm from baffle)

Good balance between detail and
oversimplification.
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Procedure Determine Speed of Sound and Pressure
Decay

• Microphone placed 2 cm from the baffle
• Data collected by the oscilloscope (?t, RMS)
• Microphone moved in increments of 2cm to final
  distance 40cm
• Data taken at each increment

No mention of frequencies, the nature of the
signal (burst, 5-cycles, amplitude), no mention
of averaging or gating. What data was taken?
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Speaker Directivity Comparison of Theory and
Experiment
Figure shows good agreement between theory and
experiment
Directivity is much higher at 4kHz vs 2 kHz
Errors might be due to ambient noise and/or
reflections off of walls, floors, etc.
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Speaker Directivity Comparison of Theory and
Experiment
Figure is too small
Figure shows good agreement between theory and
experiment
Directivity is much higher at 4kHz vs 2 kHz
Errors might be due to ambient noise and/or
reflections off of walls, floors, etc.
15
Speaker Directivity Comparison of Theory and
Experiment
Figure is too small
Figure shows good agreement between theory and
experiment
Directivity is much higher at 4kHz vs 2 kHz
Errors might be due to ambient noise and/or
reflections off of walls, floors, etc.
Better to say this in words, or move to another
slide
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Speaker Directivity Comparison of Theory and
Experiment
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Speaker Directivity Comparison of Theory and
Experiment
Better, but theres a lot of wasted space here
18
Speaker Directivity Comparison of Theory and
Experiment
19
Speaker Directivity Comparison of Theory and
Experiment
Sometimes, a grid is useful
symbol is a little light- try to darken it
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Speaker Directivity Comparison of Theory and
Experiment
discrete experimental data must use
symbols, since the lines that connect them are
only a guess
colored lines are very good, but you need to use
different linetypes if you print or show them in
black-and-white
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Speaker Directivity Comparison of Theory and
Experiment
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Speaker Directivity Comparison of Theory and
Experiment
notice how the linetypes and the grid lines
blend together
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Speaker Directivity Comparison of Theory and
Experiment
Theoretical directivity is zero, which is
infinity in dB. This distorts the scales
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Speaker Directivity Comparison of Theory and
Experiment
25
Transfer Function Amplitude and Phase for 2-DOF
System
Whats wrong with this graph?
Actual Student Work!
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Transfer Function Amplitude and Phase for 2-DOF
System
This is experimental data, but where are the
symbols?
Closing paren doesnt show
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Results 2-DOF
Heres another example. Again, there are no
data symbols and the spline fit fills in between
the measured values with curved lines.
Furthermore, The plots, especially the axis
labels/numbers, are too small.
Actual Student Work!
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Much better, but could use a more descriptive
title!
Amplitude Phase
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Often, we need to show sample calculations...
Acoustic Pressure Analysis

• Rayleigh Distance Calculation
• (2)
• Where R0 Rayleigh distance
• a Piston radius
• ? c / f Wavelength
• c Speed of sound
• f Frequency

Actual Student Work!
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SDOF System Transfer Function
Sometimes, it is necessary to show large tables
of data.
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SDOF System Transfer Function
Try to call attention to a few particular values
or rows of data.
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Conclusion

• 1-DOF System
• Natural frequency analyzed
• 2-DOF System
• An absorber was used to reduce vibrations
• Displacement-force transfer function was
  determined experimentally
• Mode shapes were determined for natural
  frequencies

Notice the correspondence between the
objectives and the conclusions