Gyre 2: Evaluation of Control Techniques for Autonomous

Free-Floating RobotsJanuary 20, 2007

Seattle Robotics Society

D. Bliss, A. Lacenski, M. Dockrey

Goals

• Followup to GYRE 1, which established the best image processing algorithm, but did not demonstrate closed-loop control

• Evaluated four control algorithms: naïve hysteresis, proportional, PI, and PID

• Tested aboard NASA’s new C-9 microgravity aircraft in August 2006.

History

• Formed in 2001• Accepted in 2002, postponed flight due to

hardware and documentation issues• GYRE 1 accepted and flew in 2003• Not accepted in 2004• Accepted in 2005, but program postponed due to

aircraft issues• Flew in 2006• DONE!

About the GYRE platform

• 50lbs, 14” cube (NASA requirements)

• Free floats within aircraft

• 3 onboard computers

• National Instruments FieldPoint interface

• 12 cold gas thrusters using air

• 3 orthogonal cameras

• Lithium-polymer batteries

Onboard Computers

• Comell Taiwan LV-671M single-board computers, mini-ITX

• Intel Pentium-M 1.6, ~2 GIPS, 128MB RAM, 1GB CompactFlash

• Cardbus Firewire interface for high-speed video• Mini-PCI 802.11b with external antennas• Onboard 100mbps Ethernet• Serial interface to NI FieldPoint

National Instruments FieldPoint

• A general-purpose industrial interface system

• One network module, up to 64 I/O modules

• Using FP-PG-522 pulse generator modules

• Allows all hard realtime to be done in FieldPoint, no need for realtime OS on SBCs

Cold Gas Thruster System

– Two 1.8L tanks at 4500 psi– Regulators on each tank reduce to 200 psi (100

psi for 2006 flights)– Low-side air manifolded and distributed to

twelve high-speed control valves with attached custom CNC-machined thrusters

– Minimum thrust bit 30 msec, about 0.06 N-S– Continuous thrust about 2N

Onboard Cameras

• Firewire

• TI chipset

• 640x480x30fps

• Custom CNC-machined enclosures

• Image recognition, feature extraction, motion vector extraction, and compensation done by onboard SBCs, one per camera

Lithium-Polymer Batteries

• The first rule of LiPo batteries:– DON’T USE LIPO BATTERIES

• 28V, ~3AH, ~45m runtime

• Horror stories

• But, great power density!

Onboard operation

• Control laptop

• Canon GL2 video camera for data collection

• Two operators

Results

Algorithm Average result Number of trials

Hysteresis 2 6

Proportional 1.57 15

Proportional-Integral 3 1

Proportional-Integral-

Derivative

3.333 3

Questions?

• David Bliss

• dbliss@u.washington.edu

• http://depts.washington.edu/gyre