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Design of Low-Power Silicon Articulated Microrobots. Richard Yeh & Kristofer S. J. Pister. Presented by: Shrenik Diwanji. Abstract
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Design of Low-Power Silicon Articulated Microrobots Richard Yeh & Kristofer S. J. Pister Presented by: Shrenik Diwanji
Abstract • To design and build a class of autonomous, low power silicon articulated micro-robots fabricated on a 1 cm2 silicon die and mounted with actuators, a controller and a solar array.
Designing • Primarily based on micro-machining • Pros • Feature sizes in sub micron • Mass production • Cons • Designing from scratch
Actuator Design • Main backbone of the robot design • Should have high W/kg3 ratio • Different types of actuators:- • Piezoelectric • Thermal and shape-memory alloy • Electromagnetic • Electrostatic
Piezoelectric actuators • Pros • Produce large force • Require low power • Cons • Require high voltage ~ 100v. • difficult to integrate with CMOS electronics
Thermal and Shape-memory alloy actuators • Pros • Robust • Easy to operate • Cons • High current dissipation ( 10s of mA)
Electromagnetic actuators • Pros • High Energy Density • Cons • Needs external magnet and / or high currents to generate high magnetic fields
Electrostatic actuators • Pros • Low power dissipation. • Can be designed to dissipate no power while exerting a force. • High power density at micro scale. • Easy to fabricate.
Electrostatic actuator design • Gap Contraction Actuator _ 1Et l v2 2 d2 Fe =
Scaling Effects Actuator force Dissipative force Gravitational force Squeeze-film damping Resistance of spring support Frequency Power density
Inch Worm Motors. Design of Inch Worm Motors Inch Worm Cycle
Power requirements • Main areas of power dissipation • CMOS controller • Actuators • Power dissipation in actuators • Weight - 0.5mN • Adhesion force - 100µN C = Total capacitance F = frequency
Designing Articulated Rigid Links • Shape of the links • Flat links • Cons • Less strength due to 2 thin poly crystalline layers • HTB • Pros • Good weight bearing capacity
Designing Articulated Rigid Links • Mounting of the solar array and the chip
Power Source • Solar array is used • η = 10 % ( max 26%) • Power density = 10mW/cm2 (100 mw/cm2, η = 26%)
Controller • Open loop control (as no sensors) • CMOS controller • Simple finite state machine • Clock generator • Charge pump
Gait speed • Gait speed = Δx/T • In one leg cycle • Δx = 100μm • T = 15 ms. • With • GCA to leg displacement factor of 1:10 • GCA gap – stop size of 2μm. • Operating frequency of 1kHz. Gait Speed = 100/15 = 7mm/s
Robot assembly • Difficulty • The size of the robot • The strength needed for perfect mechanical coupling • Solution • Flip chip bonding • Allows the micro machined devices to be transferred from substrate to another.
Conclusion • Key design issues • Actuation power density • Actuators used • Key tools • Micro machining