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Transcript of Eglin 1 Design of Acoustic Sensor Eye Housing Eglin 1 Design of Acoustic Sensor Eye Housing Group...
Eglin 1Eglin 1Design of Acoustic Design of Acoustic
Sensor Eye HousingSensor Eye Housing
Group Group Members: Members:
Erik Erik FernandezFernandez
Kevin GarveyKevin GarveyWilliam William HeffnerHeffnerBrian Brian
McMinnMcMinn
AcknowledgementsAcknowledgements
We would like to extend our sincere We would like to extend our sincere thanks and appreciation to the thanks and appreciation to the following contributors to the success following contributors to the success of our project:of our project:
Dr. Henry PfisterDr. Henry Pfister Eglin AFRL/MNEglin AFRL/MN Keith LarsonKeith Larson
Agenda Agenda
Design BackgroundDesign Background ConstraintsConstraints Material SelectionMaterial Selection Vibration Control Vibration Control Actuation SystemActuation System T-Base ArrayT-Base Array Testing and ResultsTesting and Results ConclusionConclusion
Acoustic Eye Sensor (Courtesy Dr. Pfister, Eglin AFRL)
Design BackgroundDesign Background Acoustic Eye Sensor Acoustic Eye Sensor
Frame DesignFrame Design Integrate an acoustic Integrate an acoustic
eye sensor into NASA eye sensor into NASA RDS robot. RDS robot.
Also integrate acoustic Also integrate acoustic eye sensor into VEX™ eye sensor into VEX™ robot. robot.
NASA RDS Robot
Background Cont.Background Cont. RDS (Robot Demonstration System)RDS (Robot Demonstration System)
Multiple sensor integration into test Multiple sensor integration into test bed processor.bed processor.
Acoustic Eye SensorAcoustic Eye Sensor 4 Microphone array that processes 4 Microphone array that processes
sound signals to determine location to a sound signals to determine location to a sound source.sound source.
Constraints (Tetrahedral Constraints (Tetrahedral Array)Array)
Tetrahedral Array ConstraintsTetrahedral Array Constraints Tetrahedral GeometryTetrahedral Geometry Adapt to NASA RDS RobotAdapt to NASA RDS Robot Microphone Spacing of 20 inchesMicrophone Spacing of 20 inches Collapsible remotelyCollapsible remotely Damp Mechanical VibrationsDamp Mechanical Vibrations Low Cost and LightweightLow Cost and Lightweight Utilize off-the-shelf componentsUtilize off-the-shelf components
Tetrahedron
Constraints (T-Base Constraints (T-Base Array)Array)
T-Base ConstraintsT-Base Constraints Tetrahedral GeometryTetrahedral Geometry T-base configurationT-base configuration Adapt to VEX™ RobotAdapt to VEX™ Robot Microphone spacing of 10 inchesMicrophone spacing of 10 inches Damp Mechanical VibrationsDamp Mechanical Vibrations Low Cost and LightweightLow Cost and Lightweight Utilize off-the-shelf componentsUtilize off-the-shelf components
T-Base Part
Materials SelectedMaterials Selected
Four deciding factors for material selection:Four deciding factors for material selection: Price, Availability, Weight, and Sound Conduction Price, Availability, Weight, and Sound Conduction
Materials ChosenMaterials Chosen• UHMW-PE (Ultra High Molecular Weight- Polyethylene)• ABS (Acrylanitrile Butadiene Styrene)
Materials Considered Price of Material ($/ft) for 1 inch diamterDensity of Material (lb/in 3̂) Speed of Sound Through Material (ft/s)
ABS 5.2 0.04 4254.163UHMW-PE 4.56 0.0336 2679.871
Vibration Substrates Vibration Substrates SelectedSelected
Sorbothane® Visco-elastic Sorbothane® Visco-elastic polymerpolymer Durometer 30Durometer 30 Vibration IsolationVibration Isolation
Acoustic FoamAcoustic Foam Low DensityLow Density Vibration AbsorptionVibration Absorption
http://www.sorbothane.com/
Vibration Isolation Vibration Isolation Floating BoltFloating Bolt
Sorbothane® Bushings
Flat Metal Washer
¼” Nut
¼” Bolt
Flat Metal Washer
Compressed Bushings Create Damping Region
Floating Bolt OperationFloating Bolt Operation
Shock Impact Energy In
Heat Energy Out
Heat Energy Out
Sorbothane® Bushings change mechanical energy into heat. The effect is that the input energy is displaced by an approximate 90º phase shift.
Vibration Absorption Vibration Absorption Septum BoardSeptum Board
Mic Board
Mic Adapter PlateAbsorption Foam Layer
Mic to Rod Adapter Board
Microphone Sensor Isolation Setup
Septum Board OperationSeptum Board Operation
Acoustic foam absorbs the incoming vibration impulse and acts as a filter to the frequency wave that passes to the microphone sensor.
Shock Impulse
Frequency Filtering/Absorption
Impact Impulse Impact Impulse PropagationPropagation
Microphone Sensor
Shock Impulse
Damped Impulse
Actuation SystemActuation System Stepper Motor Stepper Motor Dual Slider Track SystemDual Slider Track System
Z-2684X-V Bipolar Stepper Motor
Interior slider
Guide Pin
Lead Screw
Guide Track
External Slider
Tetrahedral Array Tetrahedral Array SystemSystem
Septum Board Slider
Guide Track
External Slider
Stepper motorFloatin
g Bolt
T-Base Array SystemT-Base Array System
Half Size Extending Rods
Half Size Center Shaft
Sorbothane® Bushing
T-Base
Floating Bolt Design
Actual Size Robot Mounting Plate
TestingTesting Vibration had to be characterized for the Vibration had to be characterized for the
RDS RobotRDS Robot 3 Tests were utilized to characterize 3 Tests were utilized to characterize
different types of vibrations:different types of vibrations: DC Motor TestDC Motor Test Rod Impact TestRod Impact Test Base Impact Base Impact
RDS Robot Test Frame
DC Motor TestDC Motor Test
Characterize the vibration Characterize the vibration propagation from the 3 DC motors propagation from the 3 DC motors attached to the RDS robot.attached to the RDS robot.
Simulated RDS base with DC motors
6 Volt DC Motors
Rod Impact TestRod Impact Test
Characterization of impulse Characterization of impulse vibration caused by a direct vibration caused by a direct extension rod obstruction impact.extension rod obstruction impact.
Simulated RDS base with Extension Rod Attached
Microphone Sensor mount
Extension Rod
Base Impact TestBase Impact Test Characterizes general vibration Characterizes general vibration
propagation through the RDS robot propagation through the RDS robot base itself.base itself.
Simulated RDS Base
RDS Test Base
DC Motor TestsDC Motor TestsMotor Vibration Test Baseline
2.75
2.8
2.85
2.9
2.95
3
3.05
3.1
0 100 200 300 400 500
Time (Scans)
Vo
ltag
e O
utp
ut
(V)
No DampingComplete System DampingBaseline = 2.95 Volts
Motor Vibration Test Baseline
2.75
2.8
2.85
2.9
2.95
3
3.05
3.1
0 100 200 300 400 500
Time (Scans)
Vo
ltag
e O
utp
ut
(V)
No DampingComplete System DampingBaseline = 2.95 Volts
500 Scans = 71.42 ms
Motor Test ResultsMotor Test Results
Design Parameter No Damping System Damping % Reduction
Microphone Excitation 1802.5 Hz 422.8 Hz 76.5 %Resonance Impulse
Magnitude 3.096 Volts 2.988 Volts 74 %
ABS Rod Impact TestsABS Rod Impact Tests
Rod Impact Test (4 Ounce Weight)
0
1
2
3
4
5
6
0 200 400 600 800 1000 1200 1400
Time (Scans)
Vo
ltag
e O
utp
ut (
V)
No Damping Impact
Complete System Damping
Baseline = 2.95 Volts
500 Scans = 71.42 ms
Rod Impact Test (4 Ounce Weight)
0
1
2
3
4
5
6
0 200 400 600 800 1000 1200 1400
Time (Scans)
Vo
ltag
e O
utp
ut (
V)
No Damping Impact
Complete System Damping
Baseline = 2.95 Volts
500 Scans = 71.42 ms
Rod Impact ResultsRod Impact Results(Critical Damping (Critical Damping
Coefficient)Coefficient)Test Type Critical Damping Coefficient
No Damping 205.2 kg/s
System Damping 1039.3 kg/s
Advantage 5 Times Better
• Critical Damping coefficient characterizes the rate at which an impulse will be damped out.
Rod Impact ResultsRod Impact Results(Settling Time and Impulse (Settling Time and Impulse
Magnitude)Magnitude)Test Parameter Settling Time Impulse Magnitude
No Damping 185.7 ms 5.457 Volts
System Damping 124.98 ms 5.361 Volts
% Reduction 33 % 4 %
• Settling time is the time it takes for an impulse wave to return to equilibrium.
• Impulse magnitude is the actual strength that an impulse imposes upon the system.
RDS Base Impact TestsRDS Base Impact TestsBase Impact Test (4 Ounce Weight)
0
1
2
3
4
5
6
0 200 400 600 800 1000 1200Time (Scans)
Vo
ltag
e O
utp
ut (
V)
No Damping
Complete System Damping
Baseline = 2.95 Volts
500 Scans = 71.42 ms
Base Impact Test (4 Ounce Weight)
0
1
2
3
4
5
6
0 200 400 600 800 1000 1200Time (Scans)
Vo
ltag
e O
utp
ut (
V)
No Damping
Complete System Damping
Baseline = 2.95 Volts
500 Scans = 71.42 ms
RDS Base Impact ResultsRDS Base Impact Results(Critical Damping (Critical Damping
Coefficients)Coefficients)Test Type Critical Damping Coefficient
No Damping 866.5 kg/s
System Damping 1978.8 kg/s
Advantage 2 Times Better
• This characterizes the rate at which the impact is mitigated through the structure before it reaches the microphone sensor.
RDS Base Impact ResultsRDS Base Impact Results(Settling Time and Impulse (Settling Time and Impulse
Magnitude)Magnitude)Test Parameter Settling Time Impulse Magnitude
No Damping 160.8 ms 5.073 Volts
System Damping 72.4 ms 3.701 Volts
% Reduction 55 % 65 %
• The majority of the vibration will be through the RDS structure itself and testing has shown a significant result in the impulse magnitude.
Rod Impact Test (Acrylic vs. Rod Impact Test (Acrylic vs. ABS)ABS)
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Test (Aluminum Rod Impact Test (Aluminum vs. ABS)vs. ABS)
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vol
tage
Out
put (
V)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vol
tage
Out
put (
V)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Test (Brass Rod Impact Test (Brass vs. ABS)vs. ABS)
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Test (Pine Rod Impact Test (Pine vs. ABS)vs. ABS)
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Rod Impact ComparisonRod Impact ComparisonRod Impact Tests (Multiple Materials)
0
1
2
3
4
5
6
0 200 400 600 800 1000Time (Scans)
Vo
lta
ge
Ou
tpu
t (V
)
Baseline = 2.905 VAcrylicAluminumBrassWoodComplete System
Material Comparison Material Comparison ResultsResults
Material Material AcryliAcrylicc
AluminAluminumum
BrassBrassWood Wood (Pine)(Pine)
ABS ABS SysteSyste
mm
Settling Settling TimeTime
114 114 msms
50.7 ms50.7 ms 110 110 msms
100 100 msms
72.4 72.4 msms
Impulse Impulse MagnitudMagnitud
ee
5.308 5.308 VV
5.308 V5.308 V 5.308 5.308 VV
5.303 5.303 VV
3.701 3.701 VV
Overall Major ResultsOverall Major Results Mitigated impulse shock Mitigated impulse shock
magnitude by 65%.magnitude by 65%. Increased Damping coefficient by Increased Damping coefficient by
80%.80%. Decreased Settling time by as Decreased Settling time by as
much as 55%.much as 55%.
ConclusionConclusion Successfully designed and built working Successfully designed and built working
prototype arrays to Eglin AFRL prototype arrays to Eglin AFRL constraints. constraints. Collapsible Tetrahedral ArrayCollapsible Tetrahedral Array
Low Cost (~$250)Low Cost (~$250) Lightweight (~2 lbs.)Lightweight (~2 lbs.) Considerably Mitigates Vibration (As described Considerably Mitigates Vibration (As described
previously)previously) Full RDS AdaptabilityFull RDS Adaptability Complete remote actuation collapsibility Complete remote actuation collapsibility
T-Base ArrayT-Base Array Considerably Lower Cost (~$25)Considerably Lower Cost (~$25) Full VEX robot adaptabilityFull VEX robot adaptability Vibration Control and LightweightVibration Control and Lightweight