Eglin 1 Design of Acoustic Sensor Eye Housing Eglin 1 Design of Acoustic Sensor Eye Housing Group Members: Erik Fernandez Kevin Garvey William Heffner Brian McMinn

Acknowledgements We would like to extend our sincere thanks and appreciation to the following contributors to the success of our project: We would like to extend our sincere thanks and appreciation to the following contributors to the success of our project: Dr. Henry Pfister Dr. Henry Pfister Eglin AFRL/MN Eglin AFRL/MN Keith Larson Keith Larson

Agenda Design Background Design Background Constraints Constraints Material Selection Material Selection Vibration Control Vibration Control Actuation System Actuation System T-Base Array T-Base Array Testing and Results Testing and Results Conclusion Conclusion Acoustic Eye Sensor (Courtesy Dr. Pfister, Eglin AFRL)

Design Background Acoustic Eye Sensor Frame Design Acoustic Eye Sensor Frame Design Integrate an acoustic eye sensor into NASA RDS robot. Integrate an acoustic eye sensor into NASA RDS robot. Also integrate acoustic eye sensor into VEX™ robot. Also integrate acoustic eye sensor into VEX™ robot. NASA RDS Robot

Background Cont. RDS (Robot Demonstration System) RDS (Robot Demonstration System) Multiple sensor integration into test bed processor. Multiple sensor integration into test bed processor. Acoustic Eye Sensor Acoustic Eye Sensor 4 Microphone array that processes sound signals to determine location to a sound source. 4 Microphone array that processes sound signals to determine location to a sound source.

Constraints (Tetrahedral Array) Tetrahedral Array Constraints Tetrahedral Array Constraints Tetrahedral Geometry Tetrahedral Geometry Adapt to NASA RDS Robot Adapt to NASA RDS Robot Microphone Spacing of 20 inches Microphone Spacing of 20 inches Collapsible remotely Collapsible remotely Damp Mechanical Vibrations Damp Mechanical Vibrations Low Cost and Lightweight Low Cost and Lightweight Utilize off-the-shelf components Utilize off-the-shelf components Tetrahedron

Constraints (T-Base Array) T-Base Constraints T-Base Constraints Tetrahedral Geometry Tetrahedral Geometry T-base configuration T-base configuration Adapt to VEX™ Robot Adapt to VEX™ Robot Microphone spacing of 10 inches Microphone spacing of 10 inches Damp Mechanical Vibrations Damp Mechanical Vibrations Low Cost and Lightweight Low Cost and Lightweight Utilize off-the-shelf components Utilize off-the-shelf components T-Base Part

Materials 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 Chosen Materials Chosen UHMW-PE (Ultra High Molecular Weight- Polyethylene) ABS (Acrylanitrile Butadiene Styrene)

Vibration Substrates Selected Sorbothane® Visco-elastic polymer Sorbothane® Visco-elastic polymer Durometer 30 Durometer 30 Vibration Isolation Vibration Isolation Acoustic Foam Acoustic Foam Low Density Low Density Vibration Absorption Vibration Absorption

Vibration Isolation Floating Bolt Sorbothane® Bushings Flat Metal Washer ¼” Nut ¼” Bolt Flat Metal Washer Compressed Bushings Create Damping Region

Floating Bolt Operation Shock Impact Energy In 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 Septum Board Mic Board Mic Adapter Plate Absorption Foam Layer Mic to Rod Adapter Board Microphone Sensor Isolation Setup

Septum 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 Propagation Microphone Sensor Shock Impulse Damped Impulse

Actuation System Stepper Motor Stepper Motor Dual Slider Track System Dual Slider Track System Z-2684X-V Bipolar Stepper Motor Interior slider Guide Pin Lead Screw Guide Track External Slider

Tetrahedral Array System Septum Board Slider Guide Track External Slider Stepper motor Floating Bolt

T-Base Array System Half Size Extending Rods Half Size Center Shaft Sorbothane® Bushing T-Base Floating Bolt Design Actual Size Robot Mounting Plate

Testing Vibration had to be characterized for the RDS Robot Vibration had to be characterized for the RDS Robot 3 Tests were utilized to characterize different types of vibrations: 3 Tests were utilized to characterize different types of vibrations: DC Motor Test DC Motor Test Rod Impact Test Rod Impact Test Base Impact Base Impact RDS Robot Test Frame

DC Motor Test Characterize the vibration propagation from the 3 DC motors attached to the RDS robot. Characterize the vibration propagation from the 3 DC motors attached to the RDS robot. Simulated RDS base with DC motors 6 Volt DC Motors

Rod Impact Test Characterization of impulse vibration caused by a direct extension rod obstruction impact. Characterization of impulse vibration caused by a direct extension rod obstruction impact. Simulated RDS base with Extension Rod Attached Microphone Sensor mount Extension Rod

Base Impact Test Characterizes general vibration propagation through the RDS robot base itself. Characterizes general vibration propagation through the RDS robot base itself. Simulated RDS Base RDS Test Base

DC Motor Tests 500 Scans = ms

Motor Test Results Design ParameterNo DampingSystem Damping% Reduction Microphone Excitation Hz422.8 Hz 76.5 % Resonance Impulse Magnitude Volts2.988 Volts 74 %

ABS Rod Impact Tests

Rod Impact Results (Critical Damping Coefficient) Test Type  Critical Damping Coefficient No Damping205.2 kg/s System Damping kg/s Advantage 5 Times Better Critical Damping coefficient characterizes the rate at which an impulse will be damped out.

Rod Impact Results (Settling Time and Impulse Magnitude) Test ParameterSettling TimeImpulse Magnitude No Damping185.7 ms5.457 Volts System Damping ms5.361 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 Tests

RDS Base Impact Results (Critical Damping Coefficients) Test Type  Critical Damping Coefficient No Damping866.5 kg/s System Damping 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 Results (Settling Time and Impulse Magnitude) Test ParameterSettling TimeImpulse Magnitude No Damping160.8 ms5.073 Volts System Damping 72.4 ms3.701 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. ABS)

Rod Impact Test (Aluminum vs. ABS)

Rod Impact Test (Brass vs. ABS)

Rod Impact Test (Pine vs. ABS)

Rod Impact Comparison

Material Comparison Results MaterialAcrylicAluminumBrass Wood (Pine) ABS System Settling Time 114 ms 50.7 ms 110 ms 100 ms 72.4 ms Impulse Magnitude V V V

Overall Major Results Mitigated impulse shock magnitude by 65%. Mitigated impulse shock magnitude by 65%. Increased Damping coefficient by 80%. Increased Damping coefficient by 80%. Decreased Settling time by as much as 55%. Decreased Settling time by as much as 55%.

Conclusion Successfully designed and built working prototype arrays to Eglin AFRL constraints. Successfully designed and built working prototype arrays to Eglin AFRL constraints. Collapsible Tetrahedral Array Collapsible Tetrahedral Array Low Cost (~$250) Low Cost (~$250) Lightweight (~2 lbs.) Lightweight (~2 lbs.) Considerably Mitigates Vibration (As described previously) Considerably Mitigates Vibration (As described previously) Full RDS Adaptability Full RDS Adaptability Complete remote actuation collapsibility Complete remote actuation collapsibility T-Base Array T-Base Array Considerably Lower Cost (~$25) Considerably Lower Cost (~$25) Full VEX robot adaptability Full VEX robot adaptability Vibration Control and Lightweight Vibration Control and Lightweight