AMOUR (Autonomous Modular Optical Underwater Robot)

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AMOUR (Autonomous Modular Optical Underwater Robot)

AMOUR with sensors in Moorea

We designed, developed and deployed an underwater sensor network capable of multi-modal perception, dual communications and mobility in the ocean. The hardware consists of static sensor network nodes and mobile robots that are networked using three communication systems: optically for underwater point-to-point transmission at 3Mb/s; acoustically for underwater broadcast communication over hundreds of meters range at 300b/s; and using radio for communication at the surface. We have demonstrated the system during experiments with this system in the ocean, in rivers, and in lakes.



AquaNodes: Underwater Sensor Network Supporting Multi-Modal Communications

Sensors drying in the sun

The sensor nodes, which were developed in our lab, package communication, sensing, and computation in a cylindrical water-tight container of 3.5in diameter and 10in height. Each unit includes an acoustic modem we designed and developed. The modem is built around a 600MHz BF533 Blackfin DSP with 64M of RAM and contains all the electronics needed to drive and receive signals from our custom-built piezoceramic transducer. The acoustic modem is an FSK modem (with the potential to extend it to MFSK), operating at 30KHz. It has a data rate of 300b/s over a 400m range verified in the ocean and in fresh water. The acoustic modem supports measuring pair-wise ranges (using time of flight), as well as one-way ranging using an on-board thermo-compensated clock. Ranging allows the sensor network to establish a systems of coordinates to localize the static nodes and to localize moving objects, such as AMOUR, underwater. The system of sensor nodes uses a self-synchronizing distributed TDMA protocol.

Each AquaNode also includes an optical modem implemented using green light. The optical modem allows short-range point-to-point communication between the underwater robot and sensor nodes with speeds over 3Mbit/s. Finally, each node contains a 1W 900MHz radio which allows long range communication at the surface.

AquaNode


The AquaNodes are built around a 32bit ARM7TDMI LPC2148 processor running at 60MHz. Each AquaNode has an on-board SD card for logging gigabytes of data, a non-volatile FRAM for storing state information, and 40K of RAM for on-board computation. A small display enables underwater feedback and monitoring of the system. Each unit includes temperature and pressure sensors, as well as inputs for a variety of analog and digital water chemistry sensors. The analog sensors are read using a 24bit analog-to-digital converter and digital sensors can be connected via UART, RS232, RS485, I2C, SPI, and other digital interfaces.

Because the nodes are light and small, they are easily deployed by manually throwing them overboard. Once deployed, the nodes are anchored with weights and form a static underwater network. This network self-localizes using a range based 3D distributed localization algorithm[1]. After localization, the nodes are able to automatically adjust their depth in the water using a winch-based depth adjustment system. By adjusting the depth the nodes are able to optimize sensing using a distributed depth adjustment algorithm. Additionally, the nodes can surface to use radio communication or to be easily recovered.



Robot

AMOUR VI with spare thrusters and human input device (HID)

The underwater sensor network supports mobile nodes such as our underwater robot called the Autonomous Modular Optical Underwater Robot (AMOUR).

The robot has all of the capabilities of the sensor boxes as well as a more advanced camera system for use in local obstacle avoidance. One of the design goals of the robot was to be inexpensive, so it does not have an expensive inertial measurement unit (IMU). Instead we rely on the range measurements we obtain to the sensor nodes to determine its trajectory through the water

The job of the robot is to travel around and download data from the senor nodes. Additionally it gives the network dynamic sampling capabilities. If an event is happening of interest the robot can move to that area to provide denser sensor sampling. We envision having many robots in the final system to provide highly dynamic sampling and faster download of the data from the static nodes.

AMOUR is composed of a main body and up to 8 external thrusters. Without payload and equipped with 5 thrusters the robot weights approximately 17.5kg and is 3kg buoyant.

The body is an acrylic cylinder, measuring 17.8cm in diameter and 72.4cm in length. The body houses a Lithium-Ion battery, battery management board, inertial measurement unit (IMU), sensor board [9], communication hub for serial devices, and a small PC. The battery has a capacity of 645Wh and amounts for a third of the weight of the robot. The battery is actuated by an electric motor and it can travel along the axis of the robot to shift the robot's center of mass [10]. At each end, the body has a two 10cm empty section that can be used for additional dry payloads. The battery management board distributes the power, measures the robot's current consumption and tracks the precise state of the battery using a charge counter. The IMU estimates the pose and the depth of the robot by fusing the raw data from 10 sensors (one pressure sensor, 3 magnetic field sensors, 3 accelerometers and 3 gyroscopes). The sensor board is used for (1) reading of GPS and marine analog and digital sensors, (2) data logging and (3) radio communications. The communication hub allows the connection of up to 16 devices (serial TLL, RS232 or RS485). The PC will be used in the future for control, high level mission planning, and online data processing of the sensory payload.

The thrusters are designed in house. Each thruster is composed of a motor controller and a 600W geared brushless DC motor driving a Kort nozzle propeller with a diameter of 9.4cm. The motor and the electronics are housed in an aluminum cylinder, with a diameter of 4.8cm and a length of 25.4cm. Each thruster can generate up to 4kg of static thrust. The thrusters receive commands via a RS485 bus.

AMOUR's configuration is very modular. The thrusters can be attached along the robot's body or to the robot's end caps. Each thruster is connected electrically to one of the 8 ports fitted on AMOUR's bottom cap. Replacing a thruster or changing the thruster configuration can be done in less than 5 minutes. AMOUR is designed to carry internal and external payloads. AMOUR's control algorithms and high power thrusters allow precise and fast manipulation of payloads of size similar to its own.


Localization and Tracking

Results of localization

To be able to find the sensor nodes the robot must know precisely where it is at all times. A passive localization and tracking algorithm we developed[2] has been implemented on this sensor network system and used to localize and track the moving robot.

We have deployed the sensor nodes and the robot in the ocean (Moorea, French Polynesia [3]), in Singapore harbor, in the river (Charles River, MA) and in a lake (Otsego, NY) and collected extensive networking and localization data for this system. Our experiments verify the theoretical predictions.

We have performed extensive communication, networking, localization and tracking experiments with four to six static sensor nodes localizing and tracking the AMOUR robot. In a lake experiment, data was collected over an 80 by 80 meter area of the lake that is 20 meters deep. The nodes were deployed to float between 3 and 5 meters below the water surface. The figure to the left shows the results. The nodes were localized using our distributed localization algorithm. AMOUR moved autonomously across this area on the surface of the water. It collected both GPS and range information by acoustic messaging as it moved. This data was then used to locate and track the position of the robot. We commanded the robot to move using its entire speed range during this experiment.

The mean location error for AMOUR was 2.5 meters (which is less than the accuracy of the GPS unit we used). Over a period of an hour there were a total of 1700 messages transmitted acoustically across the network formed by the sensor nodes and the robot. The overall success rate for message transmission was 56%.


Videos

File:ICRA2010amour.mp4
File:1docking hq.avi File:5amour starbug dock.avi
File:amour starbug cooperative.avi File:onebox.avi
File:lake results-2.avi File:moorea cut.avi

People

Current

Marek Doniec

Daniela Rus

Past

Iuliu Vasilescu

Carrick Detweiler

Daniel Gurdan

Keith Kotay

Philipp Reist

Jan Stumpf

Paulina Varshavskaya

David Wyatt

Collaborators

Peter Corke, CSIRO

Matt Dunbabin, CSIRO

Michael Hamilton, James Reserve

Roger Payne, Ocean Alliance

MIT PLUSNet Team: Henrik Schmidt, John Leonard, Alex Bahr, Joe Curcio

References

[1]

David Moore, John Leonard, Daiela Rus, Seth Teller - Robust distributed network localization with noisy range measurements
SenSys '04: Proceedings of the 2nd international conference on Embedded networked sensor systems pp. 50--61, New York, NY, USA,2004
Bibtex
Author : David Moore, John Leonard, Daiela Rus, Seth Teller
Title : Robust distributed network localization with noisy range measurements
In : SenSys '04: Proceedings of the 2nd international conference on Embedded networked sensor systems -
Address : New York, NY, USA
Date : 2004

[2]

Carrick Detweiler, John Leonard, Daniela Rus, Seth Teller - Passive mobile robot localization within a fixed beacon field
in Proceedings of the International Workshop on the Algorithmic Foundations of Robotics ,2006
Bibtex
Author : Carrick Detweiler, John Leonard, Daniela Rus, Seth Teller
Title : Passive mobile robot localization within a fixed beacon field
In : in Proceedings of the International Workshop on the Algorithmic Foundations of Robotics -
Address :
Date : 2006

[3]

Peter Corke, Carrick Detweiler, Matthew Dunbabin, Michael Hamilton, Daniela Rus, Iuliu Vasilescu - Experiments with underwater robot localization and tracking
In Proceedings of the International Conference on Robotics and Automation , Roma, Italy, April 2007
Bibtex
Author : Peter Corke, Carrick Detweiler, Matthew Dunbabin, Michael Hamilton, Daniela Rus, Iuliu Vasilescu
Title : Experiments with underwater robot localization and tracking
In : In Proceedings of the International Conference on Robotics and Automation -
Address : Roma, Italy
Date : April 2007

[4]

Matthew Dunbabin, Peter Corke, Iuliu Vasilescu, Daniela Rus - Experiments with Cooperative Control of Underwater Robots
In Proceedings of the 2006 International Symposium on Experimental Robotics , July 2006
Bibtex
Author : Matthew Dunbabin, Peter Corke, Iuliu Vasilescu, Daniela Rus
Title : Experiments with Cooperative Control of Underwater Robots
In : In Proceedings of the 2006 International Symposium on Experimental Robotics -
Address :
Date : July 2006

[5]

Iuliu Vasilescu, Keith Kotay, Daniela Rus, Matthew Dunbabin, Peter Corke - Data collection, storage, and retrieval with an underwater sensor network
SenSys '05: Proceedings of the 3rd international conference on Embedded networked sensor systems pp. 154--165, New York, NY, USA,2005
Bibtex
Author : Iuliu Vasilescu, Keith Kotay, Daniela Rus, Matthew Dunbabin, Peter Corke
Title : Data collection, storage, and retrieval with an underwater sensor network
In : SenSys '05: Proceedings of the 3rd international conference on Embedded networked sensor systems -
Address : New York, NY, USA
Date : 2005

[6]

Matthew Dunbabin, Iuliu Vasilescu, Peter Corke, Daniela Rus - Data Muling over Underwater Wireless Sensor Networks using an Autonomous Underwater Vehicle.
In Proceedings of the 2006 International Conference on Robotics and Automation , May 2006
Bibtex
Author : Matthew Dunbabin, Iuliu Vasilescu, Peter Corke, Daniela Rus
Title : Data Muling over Underwater Wireless Sensor Networks using an Autonomous Underwater Vehicle.
In : In Proceedings of the 2006 International Conference on Robotics and Automation -
Address :
Date : May 2006

[7]

Marek Doniec, Iuliu Vasilescu, Carrick Detweiler, Daniela Rus - Complete SE(3) Underwater Robot Control with Arbitrary Thruster Configurations
In Proceedings of the 2010 International Conference on Robotics and Automation , Anchorage, Alaska, May 2010
Bibtex
Author : Marek Doniec, Iuliu Vasilescu, Carrick Detweiler, Daniela Rus
Title : Complete SE(3) Underwater Robot Control with Arbitrary Thruster Configurations
In : In Proceedings of the 2010 International Conference on Robotics and Automation -
Address : Anchorage, Alaska
Date : May 2010

[8]

Marek Doniec, Iuliu Vasilescu, Carrick Detweiler, Daniela Rus, Mandar Chitre, Matthias Hoffmann-Kuhnt - Aquaoptical: A Lightweight Device for High-Rate Long-Range Underwater Point-to-Point COmmunication
Proceedings of OCEANS 2009 , Biloxi, Mississippi, October 2009
Bibtex
Author : Marek Doniec, Iuliu Vasilescu, Carrick Detweiler, Daniela Rus, Mandar Chitre, Matthias Hoffmann-Kuhnt
Title : Aquaoptical: A Lightweight Device for High-Rate Long-Range Underwater Point-to-Point COmmunication
In : Proceedings of OCEANS 2009 -
Address : Biloxi, Mississippi
Date : October 2009

[9]

Carrick Detweiler, Iuliu Vasilescu, Daniela Rus - An Underwater Sensor Network with Dual Communications, Sensing, and Mobility
OCEANS 2007 - Europe pp. 1-6, June 2007
Bibtex
Author : Carrick Detweiler, Iuliu Vasilescu, Daniela Rus
Title : An Underwater Sensor Network with Dual Communications, Sensing, and Mobility
In : OCEANS 2007 - Europe -
Address :
Date : June 2007

[10]

Iuliu Vasilescu, Carrick Detweiler, Marek Doniec, Daniel Gurdan, Stefan Sosnowski, Jan Stumpf, Daniela Rus - AMOUR V: A Hovering Energy Efficient Underwater Robot Capable of Dynamic Payloads
International Journal of Robotics Research (IJRR) ,2010
Bibtex
Author : Iuliu Vasilescu, Carrick Detweiler, Marek Doniec, Daniel Gurdan, Stefan Sosnowski, Jan Stumpf, Daniela Rus
Title : AMOUR V: A Hovering Energy Efficient Underwater Robot Capable of Dynamic Payloads
In : International Journal of Robotics Research (IJRR) -
Address :
Date : 2010
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