VAST AUAV (Variable AirSpeed Telescoping Additive Unmanned Air Vehicle)

Transcription

1 VAST AUAV (Variable AirSpeed Telescoping Additive Unmanned Air Vehicle) Michael Stern & Eli Cohen MIT Lincoln Laboratory RAPID 2013 June 11 th, 2013 This work is sponsored by the Air Force under Air Force contract number FA C The opinions, interpretations, recommendations, and conclusions are those of the authors and are not necessarily endorsed by the United States Government.

2 Introduction Increased Production of End-Use Parts Increasing UAV* Investment Percent of revenue for 3D printed parts designated for end use UAV Quantities Year Year AM** use shifting from only modeling and prototyping to include end-use part production Aviation industry transitioning to develop low risk platforms UAVs offer pilotless platforms with reduced cost and schedule Air Force s next decade procurement plan targets 90% increase in unmanned platforms *UAV (Unmanned Air Vehicle) ** AM (Additive manufacturing)

3 Project Goals 10mi Vortices formed off of Selkirk Island VAST AUAV during flight test Nov 16, 2012 Weather sensing goals Sample weather while moving slowly, remaining aero stationary Sample weather while flying quickly, remaining geo stationary Synergy between goals of AM design and UAV development Quick build time Low development cost Reduced material Lighter airframe

4 Additive Unmanned Air Vehicles (AUAVs) SULSA Wendy MUAV* Testbed University of Southampton, UK SLS** structure (Nylon) 5 pieces with printed hardware Elliptical planform University of Virginia FDM*** Structure (ABS) Hobby aircraft construction Extensive Assembly University of Malaysia Pahang FDM Structure Modular subassemblies Extensive Assembly VAST AUAV MIT Lincoln Laboratory FDM ABS construction is low cost Design utilizes COTS hardware to increase structural efficiency Vehicle does not require skilled labor to assemble *MUAV(Miniature Unmanned Air Vehicle) **SLS (Selective Laser Sintering) *** FDM (Fused Deposition Modeling)

5 VAST Aircraft Design Fuselage Telescoping Wings Parameter Value Wing Span (Extended) 80 in Wing Area (Extended) 503 in 2 Wing Span (Retracted) 56 in Wing Area (Retracted) 366 in 2 Stall Speed (Extended) 7 mph Maximum Speed (Retracted) 60 mph Weight 7 lbs Battery 2x 5400mAh 11.1v LiPo Motor Endurance (Best Cruise) Brushless 300 W 1 hour Carbon Fiber Backbone T-Tail 10 inches

6 Fuselage 3 inches CAD rendering of fuselage exploded view Flexible design allows for wide range of payloads Reconfigurable length Payload shelf for quick substitutions NACA* duct for cooling Flat surface for antenna mounting NACA* (National Advisory Committee for Aeronautics)

7 Wings and Propulsion 6 inches CAD rendering of telescoping wings in slow speed configuration, cross section of wings and wing retraction mechanism highlight Multispeed flight achieved through Change in wing area Change in exposed airfoil shape Wing Box houses retraction mechanism Multi-section wings reinforced with carbon fiber spars

8 Tail CFD* model of airspeed around VAST AUAV during flight T-Tail enables control over wide operating range Aerodynamic simulation shows front wing wake would affect low tail Control surfaces benefit from accelerated flow from prop Tradeoff between aero and mechanical design CFD* (Computational Fluid Dynamics)

9 Modular Design Frangible design Designed failure locations to prevent widespread damage Efficient to print Any part can be printed in less than 24 hours Every part can be optimally (individually) oriented Simple to modify Accelerated flight-testing phase Created payload flexibility Common interfaces between parts enable multiple designers to collaborate efficiently Photo of VAST crash Nov 1, 2012

10 Additive Manufacturing Design Process AM provides an efficient development cycle No shift to conventional manufacturing cycle required Effort invested during prototyping is conserved to final production Design for manufacturability Design for assembly Structural analysis, aero analysis

11 Design for Additive Manufacturing Design Considerations Material Extrusion Process Part Orientation Affects anisotropy Can cause features to require support Affects figure error on shapes, such as circles. Digital Design Discrete characteristics in x-y and z directions Overhanging Structures Depending on angle some overhangs self support Support Material Plan Support material is wasteful Depending on geometry it may not be necessary Build Material Support Material

12 Printing Examples

13 Printing the Fuselage Orientation Vertical build Provides hoop strength Digital Design Minimum wall thickness Discrete bulkhead thickness Overhanging Structures Self supporting chamfered ribs NACA duct Support Material Plan NACA duct close to build plane Print top hole unsupported Chamfered rib self supports Square rib requires support Figure showing internal rib cross sections 2 inches Rendering of fuselage center section

14 Printing Examples

15 Printing the Wing Orientation Vertical build No figure error on airfoil Digital Design Minimum wall thickness Overhanging Structures Top surface of wing Support Material Plan Utilize self supporting cellular structure 2 inches 2 inches Photo of wing showing internal structure CAD rendering of wing with portion of skin hidden

16 Wing Testing Rendering of wing test loading scheme Internal Structure Wings tested to determine maximum strength Five wing geometries evaluated Benchmarked against Stratasys sparse fill without carbon spar Cellular fill both with carbon spars and without them Spar and skin both with carbon spars and without them Similar strength-to-weight properties in all carbon free wings Carbon reinforced wings had markedly increased properties Average 90% increase in strength Average 70% increase in strength-to-weight Print Time (hr:mm) Part Weight (lbs) Max Load at Failure (lbs) Strengthto-Weight (lbs/lbs) Sparse Fill 16: Cellular Fill Carbon Spars 13: Cellular Fill 13: Spar and Skin Carbon Spars 8: Spar and Skin 8: Table of wing properties

17 Flight Video VAST AUAV during flight test Nov 16, 2012

18 Conclusion AM Design for End-Use Parts Investigated design for additive manufacturing for material extrusion Developed design guidelines for FDM Benefited from development process for AM end-use parts where time spent on the prototype applies directly to the production parts as well Created high strength-to-weight parts with AM Benefited from utilization of rapid development cycle for AM end-use parts VAST AUAV Conducted multiple successful flight tests Designed telescoping wing to allow for wide range of flight speed Developed modular frangible design that can be built and repaired quickly Augmented AM parts with COTS components to create efficient vehicle

19 Questions VAST AUAV during flight test Nov 1, 2012

20 Thank you! Michael Stern & Eli Cohen MIT Lincoln Laboratory Collaborators: Aaron Cusher, Caroline Lamb, Molly Gutcher, Kyle Oman, and Walter Zukowski