Design of an Autonomous Jumping Microrobot

Sarah Bergbreiter and Prof. Kris PisterBerkeley Sensor and Actuator Center

University of California, Berkeley

Motivation

• Make Silicon Move!

• Mobile Sensor Networks– Monitoring/surveillance– Search and rescue

• Bi-modal transportation– Walking, Flying

Jumping: Locomotion

• Mobility– Obstacles are large

• Efficiency– What time and energy is required to move a microrobot 1

m and what size obstacles can these robots overcome?

50 m

130 mJ

417 min

10 mg

1 cm

5 mJ

1 min

10 mg

**

1.5 mJ

15 sec

11.9 mg

Obstacle Size

Energy

Time

Mass

Hollar (Walking)

Proposed (Jumping)

Ant (Walking)

A. Lipp, H. Wolf, and F.O. Lehmann., “Walking on inclines: energetics of locomotion in the ant Camponotus," Journal of Experimental Biology 208(4) Feb 2005, 707-19.S. Hollar, "A Solar-Powered, Milligram Prototype Robot from a Three-Chip Process," in Mechanical Engineering: University of California, Berkeley, 2003.

Jumping: Challenges

• Kinetic energy for jump derived from work done by motors– High force, large throw

motors

• Short legs require short acceleration times– Use energy storage and

quick release

vlt legacc 2=

Robot Design

• Power for motors and control

• Controller to tell robot what to do

• Spring for energy storage

• Higher force, larger displacement motor

• Landing and resetting for next jump are NOT discussed

Power

Control

1 mm

Motors

Energy Storage

rubber

Power and Control: Design

• Power Design– Small mass and area – Few (or no) additional

components– Simple integration to motors– Supports multiple jumps

• Control Design– Small size– Low power– Simple integration– Programmability– Off-the-shelf

EM6580, 3.5 mg

2 m

m

1.8

mm

Bellew, Hollar (Transducers 2003), 2.3 mg

Energy Storage: Design

• Small area and mass• High efficiency• Store large amounts of energy (10s of J)

– Support large deflections (many mm) – Withstand high forces (many mN)

• Integrate easily with MEMS actuators without complex fabrication

Material E (Pa) Maximum Strain (%)

Tensile Strength (Pa)

Energy Density (mJ/mm3)

Silicon 169x109 0.6 1x109 3

Silicone 750x103 350 2.6x106 4.5

Resilin 2x106 190 4x106 4

Energy Storage: Fabrication

100 m500m

Sylgard® 186 30 m

100 m

• Stored ~ 20 J– Equivalent to 20

cm jump height

• Around 90% efficient

Actuators: Design

• Small area and mass• Low input power and moderate voltage• Reasonable speed • Do large amounts of work (10s of J) to

store energy for jump– Large displacements (5 mm)– High forces (10 mN)

• Simple fabrication

1 mm

l

+-V g

t

k

F

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

Actuators: Inchworm Motors

• Inchworm actuation accumulates short displacements for long throw

• May be fabricated in single mask SOI process

250 m

Actuators: Higher Forces

20

202

1

g

AVF ε=

gi,1 gt,f

+V

gi,0 gt,0

gt,gap

Prototypes: System level demo

• 30 V solar cells driving EM6580 microcontroller and small inchworm motor

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Prototypes: Motor + Elastomer

• Low force electrostatic inchworm motor with micro fabricated rubber band assembled into shuttle

rubber band

Prototypes: Quick Release

• Electrostatic clamps designed to hold leg in place for quick release– Normally-closed

configuration for portability

• Shot a surface mount capacitor 1.5 cm along a glass slide

• Energy released in less than one video frame (66ms)

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Conclusions

• Designed an autonomous jumping microrobot– Using rubber for energy storage– Higher force actuators

• Fabricated microrobot parts• Demonstrated system-level functionality

• Put it all together to build an autonomous jumping microrobot!

=

Acknowledgments

DARPA/SDR, NSF/COINS

Berkeley Microlab

Seth Hollar and Anita FlynnLeo Choi, Stratos Christianakis, Deepa Mahajan

Prof. Ron Fearing and Aaron Hoover