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Innovative 3D Printed Structures for Enhanced Real-Time Prognostic Health Monitoring
for Small Low Cost UAV’s
Chase Heckman • Jorge Nunez • Jesse Bok • Luis Bernardo
School of Engineering • University of California, Merced
Mission
Design
Print-N-Fly’s purpose is to develop a cost effective and easily 3D printed
modular UAV structure for rapid design implementation and ease of repairs.
This design will incorporate strategically embedded sensors for future use in
prognostic health monitoring thus enhancing airworthiness via a robust and
resilient airframe.
Background
Materials
Mechatronics, Embedded Systems, and Automation (MESA) Lab is a University of
California, Merced research lab which researches a broad range of topics including
unmanned aerial systems (UAS) for civil remote sensing applications.
Testing
Manufacturability
CAD/FEA
Embedded
Modularity
Analysis
Sensing
Section
•
Small Unmanned Aerial Vehicles (SUAVs) are
autonomously piloted aircraft, controlled by onboard
processors and GPS navigation
• SUAVS are typically custom made or RC planes
retrofitted with hardware necessary for autonomous
flight
• Typical materials are light weight composites: foam,
balsa wood, plastics, foam, and carbon fiber
• Custom made SUAVs are difficult and expensive to
manufacture
Typical Custom made
• Retrofitted RC planes limit the amount of customization
Foam UAV
and functionality of the airframe for autonomous flight
effecting payload size and flight characteristics
MESA Lab Requirements Include Developing:
1. Airworthy 3D printed small Airframe similar to the
classical RC plane the “Telemaster”
2. Stable Structure based on Modular/Segmented
Design
3. Embedded sensors for Health monitoring
(monitor/log flight stresses for post flight review)
4. Utilizing a desktop, filament extrusion Polylactic acid Telemaster RC Plane
(PLA) 3D printer supplied by MESA Lab
Methods
Print-N-Fly’s Approach to this project is composed of four tasks:
1) Materials Testing
• Comparing 3D printed plastic with common UAV
materials (balsa wood) for proof of structural stability
• Testing Types: 1) Tensile, 2) Compressive, 3) Impact
• Material Properties: Ultimate Strength, Specific
Strength, Modulus of Elasticity, Impact Strength
Qualitative failure characteristics
3) Manufacturability Analysis
• Experimentation with the filament extrusion 3D
printing method
• Determining limitations of printing shapes and
configurations (e.g. due to size , resolution, and
directional printing constraints)
• Analysis of default printing qualities
Modular Fuselage
•
Vibration Sensor
Temperature Sensor
•
Energy 20.00
(kJ/m2) 15.00
Energy
(kJ/m2) 15.00
20.00
PLA
10.00
5.00
0.00
0.00
Notched
Notched Notchless
Tensile Testing
5
0
0.05
ε (-)
Compressive Testing
Fuselage Modularity
Notchless
Tensile Testing
σ(MPa)
5
4
3
2
1
0
E=2 GPa
σ(MPa)
15
Balsa
10.00
5.00
15
4) Modularity/ Segmentation Design
• Segmenting wings, fuselage, and stabilizers to
promote:
• Rapid repair of damaged segment rather than
entire aircraft
• Modifications of baseline aircraft- ease of
segment interchangeability for customizing
aerodynamic and payload requirements
• Ease of manufacturing on small printer
Vibration Sensor Embedded Wing Segment
Charpy Impact Testing
25.00
0
E = 800 MPa
0
0.005
ε (-)
Compressive Testing
σ(MPa)
6
10
4
5
E= 200 MPa
0
0
Piezo Vibration Sensors- Locations: inner wings and fuselage.
Measurand: wing flutter, vibration due to flight maneuvers, impact
during landing/takeoff
Rotary Potentiometers- Locations: wings. Measurand: control
surface movement
Temperature Sensor- Locations: Fuselage. Measurand:
temperature of sensitive plastic at critical regions(e.g. near motor/
batteries)
Modular Resistive Network- Locations: Entire Aircraft. Measurand:
monitoring/ detecting loss or damage of segments
Modularity Design:
• modularized fuselage, wings, horizontal
and vertical stabilizers
•Carbon fiber spar for bending support of
wing
•Carbon fiber spine for support of fuselage
•M3 carbon steel threaded rods for
compression fitting of all modular component
Medium Grade Balsa
25.00
10
•
•
A single resistor and easy
release clip from network
σ(MPa)
20
Makerbot Replicator II
Mega Pro Mini
Loss of wing, fuselage, or
stabilizer segment results in a
break in the circuit/disconnected
resistor near the damaged
segment due to easy release clip.
Change in resistance is measured
to determine the modular
segment of breakage.
Charpy Impact Testing
2) Embedded Sensors/ Data logging
• Designing/printing sensor compartments and
convenient holders for ease of embedding
• Capability of logging in-flight health for post flight
review/proof of structural stability
Sensor Data logging
Sensors/ Electronics:
•Processor: Arduino Mega Pro Mini
•Data Logging: OpenLog Mini SD Card
•Other Hardware: multiplexers (expandable inputs) , physical filters (signal
processing)
Modular Resistive Network & Sensor Map
Medium Quality Extruded PLA
Instron Tensile Tester
Manufacturing/ Material Property Constraints:
Build Volume- 11.2 L x 6.0 W x 6.1 H in
Time- Slow print times( dependant on quality settings)
Material Properties of PLA
• Brittle behavior (little deformation or sign of weakening before
failing)
• Small notches/ printing errors result in large stress concentrators
• Denser than Balsa(0.6-1.2 g/cm^3 compared to 0.16 g/cm^3)
• Low Melting Temperature (140° F)
3D Printing Fuselage
• Warping during printing
0.05
Conclusion & Future Direction
• 3D printing SUAVs at the desktop level is not at level of expectations yet due to:
•Very Slow Build Times •Unfeasible printing of numerous classical airframe designs
•Strong material/capable of withstanding flight load, yet too heavy for light weight applications
•Low Weight alternatives must be developed
1) Foam/ Plastic Hybrid Plane 2) Thin Plastic Skin/Spray Foam 3) Non-fixed wings UAVs
Future direction in printing SUAVs at the research level include:
•Research into similar higher throughput 3D printers for more rapid SUAV printing
•Combining 3D printing with classical manufacturing/ materials (foam, carbon fiber skeletons,
plastic molding) for lighter weight alternatives
•Experimenting further into embedded sensors for prognostic health monitoring
•Developing a full scale ready-for-flight model for in flight testing
Acknowledgements
2
ε (-)
Wing Modularity with carbon fiber spar
and threaded rods
E=100 MPa
0
0
0.5
ε (-)
Team Print-N-Fly Members:
Chase Heckman [email protected]
Jesse Bok
[email protected]
Jorge Nunez
[email protected]
Luis Bernardo
[email protected]
MESA Lab Advisors:
Brandon Stark
Dr. YangQuan Chen