MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Cooperative Navigation for Groups of Autonomous Underwater Vehicles

ASAP Hot Wash Meeting – November 2006

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

What navigation information do we have?

GPS:• Only for surface(d) vehicles

Dead-reckoning:• Compass+speed est.

→ Error: 10% dist. traveled• Doppler Velocity Logger

→ Error: 1% dist. traveled→ Distance < 200 m to bottom or surface

• Inertial Navigation System→ Error: 0.2% dist. traveled→ Expensive ($100,000)

Navigation error grows without bound for DR, DVL and INS !

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

How about Sharing Navigation Information

Other vehicles may know better where they are and share this information

Examples:• Solar AUV on surface• Surfaced glider• AUV with more

sophisticated INS

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Requirements for Cooperative Navigation

• Acoustic modem (WHOI):– Maximum range: 200 m - 4 km– Maximum data rate: 3 bytes/s - 1 kByte/s– Power consumption: 100 mW in receive mode

• Precise clock– Synchronized at surface to GPS clock– Drift O(Milliseconds per hour)– Enable one way ranging to transmitting vehicles

• Bandwidth for transmitted information– Position, position uncertainty, (heading, pitch, speed)– Necessary information is contained in most CCL packages– Vehicle-to-vehicle range for free

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Cooperative Navigation Research at MIT

• ASAP/MB06 experiment in Monterey, CA, August 2006:

Kayak to AUV

• Boston: (In cooperation

with Bluefin)

Kayak to Kayak Kayak to Glider

Alexander Bahr, John J. Leonard, Cooperative Localization for Autonomous Underwater Vehicles, In Proceedings of the 10th International Symposium on Experimental Robotics (ISER) , Rio de Janeiro, Brasil, July 2006

• Publications:

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Joint Kayak-Glider Experiment at MB06

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Kayak to Glider Ranges

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Upcoming

• Theory and Algorithms– Development of new Cooperative Navigation algorithms– Comparing performance by post processing collected data sets– Defining the minimal amount of necessary information which

needs to be transferred

• Experiments– AUVs:

• Kayak to AUV in real-time, AUV to AUV (first post-processing, then real-time)

– Glider:• Dedicated Cooperative Navigation experiment with gliders• Kayak to glider, glider to glider (real-time, post-processing)

MIT Computer Science & Artificial Intelligence LaboratoryMIT Dept. of Mechanical Engineering

Autonomous CTD casts

Kayak outfitted with CTD on winch (70 m cable, 10 min/station)

• Predetermined pattern (Iuliu Vasilescu)

• Autonomous gradient following (Don Eickstedt)