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Scaling Down - The Optimal Choice?

Scaling Down - The Optimal Choice?. Fritz B. Prinz Departments of Mechanical Engineering and Materials Science and Engineering Stanford University Stanford, CA 94 305. Outline. Scaling laws Physics Engineering performance (power, power density) Mechanical tolerances

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Scaling Down - The Optimal Choice?

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  1. Scaling Down - The Optimal Choice? Fritz B. Prinz Departments of Mechanical Engineering and Materials Science and Engineering Stanford University Stanford, CA 94 305

  2. Outline • Scaling laws • Physics • Engineering performance (power, power density) • Mechanical tolerances • Manufacturing Processes • Examples • Turbine engine • Mites (millimeter sized flaps) • Mesicopter

  3. A World Apart 10-4mm-1 10-1mm-1 104 - 102

  4. Scaling of Strength and Stiffness Failure Load Failure Load per Weight Bending Stiffness per Weight Beam

  5. Scaling of Moving Objects • Find relation between: • Mass m • Length l • Time t

  6. Physics of Scaling(forget heat loss)

  7. Scaling of Length and Time k = 2 elastic K= -1 electro - static motor, gravity (Kepler’s third law)

  8. Scaling of Mass For v << c Relativisitic:

  9. Scaling of Power

  10. Electro Static Motors In theory: Assuming all dimensions e.g. gaps can be scaled down

  11. Constant Field In practice: E = constant

  12. Scaling of Critical Dimensions? Electro static /magnetic motors l Tolerance

  13. A Manufacturing Issue Determined by manufacturing process Determines quality of machine Traditional mechanical machines Integrated circuits May not be achievable Even

  14. Turbine Combustion Engines Power Density (1/l) - Thrust to Weight T/W = 5.6 T/W= 7.6

  15. Operating Temp. (OC) Current (metal) design Design incorporating ceramics M-Dot Micro Engine for Drone Aircraft Weight (g) Thrust-to-weight ratio Thrust (N)

  16. Shape Deposition Manufacturing ( SDM) From RP and CNC to . . . RP CNC 1960 1990 2000

  17. Sangkyun Kang: Mold Shape Deposition Manufacturing • Builds wax molds via SDM using Soldermask temporary part material • Gel cast ceramic slurry into • sacrificial mold

  18. Ceramic Inlet Nozzle Fully dense Silicon Nitride Strength ~ 400 - 600 Mpa as sintered RMS ~ 0,5 micro meter

  19. ‘Shape Assembled’ Mechanism

  20. Micro Flaps for Aero Elastic Control • Maximize flight time of Unmanned Air Vehicle (UAV) Front view

  21. Suggested Solution • Aeroelastic control using trailing edge effects • Concept • Span-wise lift control via micro-flaps Micro-flaps

  22. Flap Surface 6 mm Airfoil Approach • Design & Manufacture Micro-flaps Requirements • Small size (6 mm) • Large deflection (± 75°) • Frequency (10s HZ) • Material strength

  23. Actuating Mechanism

  24. 1 2 3 5 4 6 Build Sequence in SDM

  25. SDM Fabrication of Multiple Flaps

  26. Micro Flap for Aero - Elastic Control Clearance ~ 50 micron

  27. The Mesicopter: a Miniature Helicopter

  28. Aerodynamics • New results for very low Re airfoils • Very thin sections required • Maximum lift increases as Re decreases below 10,000

  29. Rotor Optimization • Chord, twist, RPM, blade number designed using nonlinear optimization • 3D analysis based on Navier-Stokes section data • Rotor matched with measured motor performance (50 000rpm)

  30. Aerodynamics • Navier-Stokes analysis of rotor sections at unprecedented low Reynolds number • Novel results of interest to Mars airplane program • Nonlinear rotor analysis and optimization code

  31. SDM Rotor Manufacturing 1. Micro-machine bottom surface of rotor on wax 2. Cast epoxy 3. Remove excess epoxy 4. Machine top surface of rotor 5. Melt wax

  32. Scaled Down Mesicopter • Insect-Scale Aerodynamics • 3D Micro-Manufacturing • Power / Control / Sensors

  33. Mesomotor Rotor Stator Anker- spule REM-Aufnahme des 2mm-Motors Explosions- ansicht des Motors

  34. Shaping of Electrodes Sputtering of seed layer SEM Micro- graph of etched silicon Plating SEMMicro- graph of plated electrode

  35. EDM of Amorphous Metals Electro Discharge Machining

  36. Massively Parallel Mechanical Systems One Electro Static Motor Many Electro Static Motors

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