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Microrobotics

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  1. Microrobotics ES159/259

  2. Updates • Lab #4 results • Lab #5 starts next week (last lab) • Instructions distributed today • HW #5 due today • HW #6 distributed today (last HW) ES159/259

  3. Introduction to Microrobotics • The physics of scaling • Fabrication methods • MEMS • SCM • Case studies • MEMS gyroscope • MEMS crawling microrobot • The Harvard Microrobotic Fly ES159/259

  4. The physics of scaling • How can we quantify the effects of various forces as some characteristic dimension changes? • Think of size as a scalar variable s representing the characteristic length • Now how do various forces scale as a function of s? • Electromagnetic: s4 • Electrostatic (constant field): s2 • Electrostatic (increasing field): s1 • Surface tension: s1 • Surface friction: s2 • Inertial forces: s3 ES159/259

  5. Fabrication paradigms • To create micromechanical structures, we need novel fabrication techniques • Result in feature sizes ranging from sub micron to centimeter: • MEMS (Micro ElectroMechanical Systems) • ~0.01µm to 10mm • Derived from IC processes • SCM (Smart Composite Microstructures) • ~1µm to 10cm • Rapid prototyping with high performance materials ES159/259

  6. A brief history of MEMS • 1750s first electrostatic motors (Benjamin Franklin, Andrew Gordon) • 1824 Silicon discovered (Berzelius) • 1927 Field effect transistor patented (Lilienfield) • 1947 invention of the transistor (made from germanium) • 1954 Smith, C.S., "Piezoresistive effect in Germanium and Silicon, Physical Review, 94.1, April 1954. • 1958 silicon strain gauges commercially available • 1961 first silicon pressure sensor demonstrated (Kulite) • 1967 Invention of surface micromachining (Nathanson, Resonant Gate Transistor) • 1970 first silicon accelerometer demonstrated (Kulite) • 1977 first capacitive pressure sensor (Stanford) • 1980 Petersen, K.E., "Silicon Torsional Scanning Mirror", IBM J. R&D, v24, p631, 1980. • 1982 disposable blood pressure transducer (Foxboro/ICT, Honeywell, $40) • 1982 active on-chip signal conditioning • 1984? First polysilicon MEMS device (Howe, Muller ) • 1988 Rotary electrostatic side drive motors (Fan, Tai, Muller) • 1989 Lateral comb drive (Tang, Nguyen, Howe) • 1991 polysilicon hinge (Pister, Judy, Burgett, Fearing) • 1992 Grating light modulator (Solgaard, Sandejas, Bloom) • 1992 MCNC starts MUMPS • 1993? first surface micromachined accelerometer sold (Analog Devices, ADXL50) • 1994 XeF2 used for MEMS ES159/259

  7. Early Semiconductor Fabrication J. Bardeen, W.H. Brattain, “The first transistor, a semiconductor triode”, Phys. Rev., 74, 230 (1948). ES159/259

  8. Intel 133 MHzPentium Processor 3.3 million transistors0.35 micron lithography4 layer metalizationFirst silicon: May 1995 ES159/259

  9. Fabrication • IC Fabrication • Deposition • Lithography • Removal • Bulk micromachining • Crystal planes • Anisotropic etching • Deep Reactive Ion Etching • Surface micromachining • Sacrificial etching • Molding • Bonding ES159/259

  10. Wafers Deposition Lithography Etch Chips Process Flow • Integrated Circuits and MEMS identical • Process complexity/yield related to # trips through central loop ES159/259

  11. Materials • Metals • Al, Au, Cu, W, Ni, TiNi, NiFe, • Insulators • SiO2 - thermally grown or vapor deposited (CVD) • Si3N4 - CVD • Polymers • The King of Semiconductors: Silicon • stronger than steel, lighter than aluminum • single crystal or polycrystalline • 10nm to 10mm ES159/259

  12. Foundry Services and Standard Processes • MUMPS • 3 level poly, no electronics • started in 1992, now 6? runs per year • LIGAMUMPS • single level metal, no electronics • Sandia • 5 level poly, no electronics • 1 level poly w/ quality CMOS • CMOS + post-processing • EDP, TMAH, XeF2 (Parameswaran) • Plasma (Fedder) ES159/259

  13. MUMPS process flow ES159/259

  14. MUMPS process flow ES159/259

  15. MUMPS process flow ES159/259

  16. Sandia National Lab 5 layer polysilicon 5-Level Polysilicon surface Micromachine Technology: Application to Complex Mechanical Systems M. Steven Rodgers and Jeffry J. Sniegowski Solid-State Sensor and Actuator Workshop Hilton Head 1998 ES159/259

  17. Smart Composite Microstructures • Fills the gap between MEMS and ‘macro’-scale manufacturing techniques (i.e. machine shops) • Involves the use of laminated, laser-micromachined components • Laser micromachine the various components ES159/259

  18. To create rigid links and compliant joints Composite prepreg Laser micromachine Deposit thin film polymer Cure/release Micromachine mirrored version Cure release To create actuators Composite prepreg Deposit passive layers Deposit electroactive materials Deposit passive layers Flip and repeat Cure Release SCM • Layup/deposit polymers and other layers ES159/259

  19. SCM • Cure and release • Follow the cure cycle of the matrix material • Apply even curing pressure 2D vacuum bagging apparatus Computer controlled pressurized oven ES159/259

  20. Materials • Metals • Cu, Stainless, Brass • Ceramics • Piezoceramics • Polymers • Polyimide • polyester • Composites • Carbon fiber • Glass fiber • Boron fiber ES159/259

  21. Case Study: MEMS gyroscopes • Detect the Coriolis force acting on a proof mass due to angular velocities • The Coriolis force is defined by: • Thus the proof mass must be excited to a known (or measured) velocity • Then we can detect this force with a number of transducers • e.g. capacitive sensor, strain sensor, etc ES159/259

  22. Digital Output MEMS Gyroscope Chip Proof Mass SenseCircuit Rotation induces Coriolis acceleration Electrostatic Drive Circuit J. Seeger, X. Jiang, and B. Boser ES159/259

  23. 1mm Drive 0.01Å Sense MEMS Gyroscope Chip J. Seeger, X. Jiang, and B. Boser ES159/259

  24. Case Study: A walking silicon microrobot • Created by Prof. Kris Pister, U.C. Berkeley Microlab • Has the goal of creating a crawling microrobot that is fully autonomous: • Onboard power and control • Uses MEMS processes and standard IC processes • Has shown successful 2D motion ES159/259

  25. 1mm Silicon Inchworm Motors ES159/259

  26. Legs Solar Cells CMOS Sequencer Motors 8.6 mm ES159/259

  27. Microrobot – Three Processes “The Actuation” – Hinges, Motors, Legs, Frame “The Power” – Solar Cell Arrays and High Voltage Transistors “The Brain” - CMOS Digital Circuits ES159/259

  28. Assembly CMOS Chip Solar Cell/High Voltage Chip Robot Legs and Motors Chip • Affix robot to wax for wirebonding • 21 wirebonds ES159/259

  29. Robot Leg Layout Inchworm Motor Drive Actuator Clutch Actuators Shuttle Preset Structure Leg and Linkage ES159/259

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  37. Design of 2DOF Leg Poly Crossover Knee Shuttles Tendons Foot Hip ES159/259

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  39. Case Study: The Harvard Microrobotic Fly • Goal: create a robotic insect capable of sustained autonomous flight • Key specs: 3cm wingspan, 60mg, 2 wings ES159/259

  40. Wing rotation and the aerodynamic basis of insect flight • Due to the small size, insects operate in a more viscous environment ES159/259

  41. Wing rotation and the aerodynamic basis of insect flight • Thoracic deformations produce the bulk of the mechanical work, smaller tuning muscles alter the thrust ES159/259

  42. Components • Four primary mechanical components: • Airframe • Actuator • Transmission • Airfoils ES159/259

  43. Actuation • High power density piezoelectric bending cantilevers • Key specs: • 40mg • ~400W/kg (as good as best DC motors at any scale) • ~2kHz dynamic range • Scalable and tailorable ES159/259

  44. Results • Wing stroke nearly identical to biological counterparts ES159/259

  45. Results • Wing stroke nearly identical to biological counterparts ES159/259

  46. Results • Liftoff! • The world’s first demonstration of an at-scale robotic insect that can produce sufficient thrust to accelerate vertically • Every component created with SCM ES159/259

  47. Digital Light Processor(Texas Instruments) ES159/259

  48. Next class… • Outline of active research areas • Mobile robot navigation • Sensors and actuators • Computer vision • Microrobotics • Surgical robotics • Grasping/teletaction/haptics ES159/259