To fully understand the ocean environment requires sensing the full water column. Utilizing a depth adjustment system on an underwater sensor network provides this while also improving global sensing and communications. This paper presents a depth adjustment system for waters up to 50 m deep that connects to the aquanode sensor network nodes. We performed experiments characterizing and demonstrating the functionality of the depth adjustment system. We discuss the application of this device in improving acoustic communication and also verify the functionality of a decentralized depth adjustment algorithm that optimizes the placement of the nodes for collecting sensing data.

@article{iuliu-amt12,
  author = {C. Detweiler and M. Doniec and I. Vasilescu and D. Rus},
  title = {Autonomous Depth Adjustment for Underwater Sensor Networks: Design and Applications},
  journal = {IEEE/ASME Transactions on Mechatronics},
  year = {2012},
  volume = {17},
  number = {1},
  pages = {16-24},
  url = {http://dspace.mit.edu/openaccess-disseminate/1721.1/72509},
  doi = {http://doi.org/10.1109/TMECH.2011.2175003}
}

Capturing color in water is challenging due to the heavy non-uniform attenuation of light in water across the visible spectrum, which results in dramatic hue shifts toward blue. Yet observing color in water is important for monitoring and surveillance as well as marine biology studies related to species identification, individual and group behavior, and ecosystem health and activity monitoring. Underwater robots are equipped with motor control for large scale transects but they lack sensors that enable capturing color-accurate underwater images. We present a method for color-accurate imaging in water called perceptual adaptive illumination. This method dynamically mixes the illumination of an object in a distance-dependent way using a controllable multi-color light source. The color mix compensates correctly for color loss and results in an image whose color composition is equivalent to rendering the object in air. Experiments were conducted with a color palette in the pool and at three different coral reefs sites, and with an underwater robot collecting image data with the new sensor.

@inproceedings{iuliu-rss10,
  author = {Iuliu Vasilescu and Carrick Detweiler and Daniela Rus},
  title = {Color-Accurate Underwater Imaging using Perceptual Adaptive Illumination},
  booktitle = {Proc. of Robotics: Science and Systems (RSS 2010)},
  year = {2010},
  url = {http://iuliu.com/pub/RSS10 Acurate Colors Underwater.pdf}
}

We present a modular sensor network platform capable of supporting a wide range of applications. We developed a platform to support a broad spectrum of scenarios, instantiating our system for applications on the ground, in the water, and in the air. Our system has operated in the field for over 240 days with month long continuous deployments, measuring positions, temperatures, pressures, and rainfall, while computing cattle behaviors, event locations, and future river level. We use this experimental experience to discuss the lessons learned in designing and using a modular and multi-functional system.

@inproceedings{iuliu-hotemnets10-2,
  author = {Elizabeth Basha and Marek Doniec and Carrick Detweiler and Iuliu Vasilescu and Daniela Rus},
  title = {Using a Multi-functional Sensor Network Platform for Large-Scale Applications to Ground, Air, and Water Tasks},
  booktitle = {Proceedings of 2010 ACM Workshop on Hot Topics in Embedded Networked Sensors (HotEMNETS)},
  year = {2010},
  url = {http://iuliu.com/pub/HOTEMNETS10-SN-Platform.pdf}
}

In this paper we develop algorithms and hardware for the autonomous gathering of cattle. We present a comparison of three different autonomous gathering algorithms that employ sound and/or electric stimuli to guide the cattle. We evaluate these algorithms in simulation by extending previous behavioral simulations for cattle. We implemented one of these algorithms and present data from experiments in which cattle were equipped with sensor nodes that allowed cueing with sound and electric stimuli. We discuss the minimum requirements for algorithms and hardware for autonomous gathering.

@inproceedings{iuliu-hotemnets10-1,
  author = {Marek Doniec and Carrick Detweiler and Iuliu Vasilescu and Dean Anderson and Daniela Rus},
  title = {Autonomous Gathering of Livestock Using a Multi-functional Sensor Network Platform},
  booktitle = {Proceedings of 2010 ACM Workshop on Hot Topics in Embedded Networked Sensors (HotEMNETS)},
  year = {2010},
  url = {http://iuliu.com/pub/HOTEMNETS10-Gathering.pdf}
}

This paper describes AquaOptical, an underwater optical communication system. Three optical modems have been developed:  a  long  range  system,  a  short  range  system,  and  a  hybrid  system. We describe their  hardware  and  software  architectures and  highlight  trade-offs.  We  present  pool  and  ocean experiments  with  each  system.  In  clear  water,  AquaOptical  achieved  a  data  rate  of  1.2Mbit/sec  at distances up to 30m. In water with visibility estimated at 3m, AquaOptical achieved communication at data rates of 0.6Mbit/sec at distances up to 9m.

@article{iuliu-mtsj10,
  author = {Marek Doniec and Carrick Detweiler and Iuliu Vasilescu and Mandar Chitre and Matthias Hoffmann-Kuhnt and Daniela Rus},
  title = {AquaOptical: A Lightweight Device for High-Rate Long-Range Underwater Point-to-Point Communication},
  journal = {Marine Technology Society Journal},
  year = {2010},
  volume = {9},
  pages = {55-65},
  url = {http://iuliu.com/pub/MTSJ10-AquaOptical-draft.pdf}
}

To fully understand the ocean environment requires sensing the full water column. Utilizing a depth adjustment system on an underwater sensor network provides this while also improving global sensing and communications. This paper presents a depth adjustment system for waters of up to 50m deep that connects to the AquaNode sensor network. We performed experiments characterizing the system and demonstrating its functionality. We discuss the application of this device in improving acoustic communication.

@inproceedings{iuliu-wuwnet10,
  author = {Carrick Detweiler and Marek Doniec and Iuliu Vasilescu and Elizabeth Basha and Daniela Rus},
  title = {Autonomous Depth Adjustment for Underwater Sensor Networks},
  booktitle = {WuWNet},
  year = {2010},
  url = {http://iuliu.com/pub/WUWNETS10-Depth-Adjustment.pdf}
}

Underwater vehicles are typically operated using a tether or a slow acoustic link. We present an underwater optical communication system that enables a high-throughput and low-latency link to an underwater robot. The optical link allows the robot to operate in cluttered environments without the need for a tether. We demonstrate the performance of the system in a number of experiments which characterize the optical link and demonstrate remote control of the robot using a human input device.

@inproceedings{iuliu-iros10,
  author = {Marek Doniec and Carrick Detweiler and Iuliu Vasilescu and Daniela Rus},
  title = {Using Optical Communication for Remote Underwater Robot Operation},
  booktitle = {Proc. of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2010)},
  year = {2010}
}

We present a control algorithm for autonomous underwater robots with modular thruster configuration. The algorithm can handle arbitrary thruster configurations. It maintains the robot’s desired attitude while solving for translationalmotion. The attitude can be arbitrarily chosen from the special orthogonal group SO(3) allowing the robot all possible orientations. The desired translational velocities can be chosen from R(3) allowing the robot to follow arbitrary trajectories underwater. If the robot is not fully holonomic then the controller chooses the closest possible solution using least squares and outputs the error vector. We verify the controller with experiments using our autonomous underwater robot AMOUR. We achieve roll errors of 1.0 degree (2.1 degrees standard deviation) and pitch errors of 1.5 degrees (1.8 degrees standard deviation). We also demonstrate experimentally that the controller can handle both nonholonomic and fully holonomic thruster configurations of the robot. In the later case we show how depth can be maintained while performing 360 degree rolls. Further, we demonstrate an input device that allows a user to control the robot’s attitude while moving along a desired trajectory.

@inproceedings{iuliu-icra10,
  author = {Marek Doniec and Iuliu Vasilescu and Carrick Detweiler and Daniela Rus},
  title = {Complete SE(3) Underwater Robot Control with Arbitrary Thruster Configurations},
  booktitle = {Proc. of IEEE International Conference on Robotics and Automation (ICRA)},
  year = {2010},
  url = {http://iuliu.com/pub/ICRA10-amour-final-submission-20100208.pdf}
}

In this paper we describe the design and control algorithms of Amour, a low-cost autonomous underwater vehicle (AUV) capable of missions of marine survey and monitoring. Amour is a highly maneuverable robot capable of hovering and carrying dynamic payloads during a single mission. The robot can carry a variety of payloads. It uses internal buoyancy and balance control mechanisms to achieve power efficient motions regardless of the payload size. Amour is designed to operate in synergy with a wireless underwater sensor network (WUSN) of static nodes. The robot's payload was designed in order to deploy, relocate and recover the static sensor nodes. It communicates with the network acoustically for signaling and localization and optically for data muling. We present control algorithms, navigation algorithms, and experimental data from pool and ocean trials with Amour that demonstrate its basic navigation capabilities, power efficiency, and ability to carry dynamic payloads.

@article{iuliu-ijrr10,
  author = {Iuliu Vasilescu and Carrick Detweiler and Marek Doniec and Daniel Gurdan and Steffan Sosnowski and Jan Stumpf and and Daniela Rus},
  title = {Amour V: a Hovering Energy Efficient Underwater Robot Capable of Dynamic Payloads},
  journal = {The International Journal of Robotics Research},
  year = {2010},
  volume = {0},
  url = {http://iuliu.com/pub/IJRR10draft%20Amour%20v%20a%20Hovering%20Energy%20Efficient%20Underwater%20Robot%20Capable%20of%20Dynamic%20Payloads.pdf}
}

This paper describes AquaOptical, an underwater optical communication system and compares its communication performance against other underwater acoustic communication systems. We describe AquaOptical’s hardware and communication software and discuss experiments. In clear water AquaOptical was tested to achieve a data rate of 1.2Mbit/sec at distances up to 30m. The system was not tested beyond 30m. In water with visibility estimated at 3m AquaOptical achieved communication at data rates of 0.6Mbit/sec at distances up to 9m.

@inproceedings{iuliu-oceans09,
  author = {Marek Doniec and Vasilescu, Iuliu and Detweiller, Carrick and Mandar Chitre and Matthias Hoffmann-Kuhnt and Rus, Daniela},
  title = {AquaOptical: A Lightweight Device for High-rate Long-range Underwater Point-to-Point Communication},
  booktitle = {OCEANS US},
  year = {2009},
  url = {http://iuliu.com/pub/OCEANS09%20AquaOptical%20A%20Lightweight%20Device%20for%20High-rate%20Long-range%20Underwater%20Point-to-Point%20Communication.pdf}
}

In this paper we describe cooperative control algorithms for robots and sensor nodes in an underwater environment. Cooperative navigation is defined as the ability of a coupled system of autonomous robots to pool their resources to achieve long-distance navigation and a larger controllability space. Other types of useful cooperation in underwater environments include: exchange of information such as data download and retasking; cooperative localization and tracking; and physical connection (docking) for tasks such as deployment of underwater sensor networks, collection of nodes and rescue of damaged robots. We present experimental results obtained with an underwater system that consists of two very different robots and a number of sensor network modules. We present the hardware and software architecture of this underwater system. We then describe various interactions between the robots and sensor nodes and between the two robots, including cooperative navigation. Finally, we describe our experiments with this underwater system and present data.

@article{iuliu-ijrr09,
  author = {Dunbabin, Matthew and Corke, Peter and Vasilescu, Iuliu and Rus, Daniela},
  title = {Experiments with Cooperative Control of Underwater Robots},
  journal = {The International Journal of Robotics Research},
  publisher = {Sage Publications, Inc.},
  year = {2009},
  volume = {28},
  number = {6},
  pages = {815--833},
  url = {http://iuliu.com/pub/IJRR08%20Experiments%20with%20Cooperative%20Control%20of%20Underwater%20Robots.pdf},
  doi = {http://dx.doi.org/10.1177/0278364908098456}
}

This thesis presents a novel approach to long-term marine data collection and monitoring. Long-term marine data collection is a key component for understanding planetary scale physical processes and for studying and understanding marine life. Marine monitoring is an important activity for border protection, port security and offshore oil field operations. However, monitoring is not easy because salt water is a harsh environment for humans and for instruments. Radio communication and remote sensing are difficult below ocean surface. <p>Our approach to ocean data collection relies on the integration of (1) a network of underwater sensor nodes with acoustic and optical communication, (2) an autonomous underwater vehicle (AUV) and (3) a novel sensing device. A key characteristic is the extensive use of visible light for information transfer underwater. We use light for sensing, communication and control.<p>We envision a system composed of sensor nodes that are deployed at static locations for data collection. Using acoustic signaling and pairwise ranging the sensor nodes can compute their positions (self-localize) and track mobile objects (e.g., AUVs). The AUV can visit the sensor nodes periodically and download their data using the high speed, low power optical communication. One consequence of using optical communication for the bulk of the data transfer is that less data needs to be transferred over the acoustic links, thus enabling the use of low power, low data rate techniques. For navigation, the AUV can rely on the tracking information provided by the sensor network. In addition, the AUV can dock and transport sensor nodes efficiently, enabling their autonomous relocation and recovery. The main application of our system is coral reef ecosystem research and health monitoring. In this application the robot and the sensor nodes can be fitted with our novel imaging sensor, capable of taking underwater color-accurate photographs for reef health assessment and species identification.<p>Compared to existing techniques, our approach: (1) simplifies the deployment of sensors through sensor self-localization, (2) provides sensor status information and thus enables the user to capture rare events or to react to sensor failure, (3) provides the user real time data and thus enables adaptive sampling, (4) simplifies mobile sensing underwater by providing position information to underwater robots, (5) collects new types of data (accurate color images) through the use of new sensors.<p>We present several innovations that enable our approach: (1) an adaptive illumination approach to underwater imaging, (2) an underwater optical communication system using green light, (3) a low power modulation and medium access protocol for underwater acoustic telemetry, (4) a new AUV design capable of hovering and of efficiently transporting dynamic payloads.<p>We present the design, fabrication and evaluation of a hardware platform to validate our approach. Our platform includes: (1) a wireless underwater sensor network composed of (2) an underwater vehicle capable of autonomous navigation, data muling, docking and efficient transport of dynamic payloads and (3) AquaLight an underwater variable-spectrum Xenon strobe which enables underwater color accurate photography. We use this platform to implement and experimentally evaluate our algorithms and protocols.

@phdthesis{vasilescu09,
  author = {Iuliu Vasilescu},
  title = {Using Light Underwater: Devices, Algorithms and Systems for Maritime Persistent Surveillance},
  school = {MIT},
  year = {2009},
  url = {http://iuliu.com/pub/iuliu-vasilescu-phd-eecs-2009.pdf}
}

We have developed an underwater robot that can pick up and place objects during an autonomous underwater mission. This robot will have changing weight and dynamics during a mission. We have developed an efficient method for buoyancy control to achieve adaptation to weight changes without the need to increasing the work of the robot’s thruster system. In this paper we describe the mechanism used for buoyancy and balance control. We also describe the adaptive control algorithms and data from physical experiments.

@inproceedings{iuliu-iser08,
  author = {Carrick Detweiler and Stefan Sosnowski and Iuliu Vasilescu and Daniela Rus},
  title = {Saving Energy with Buoyancy and Balance Control for Underwater Robots with Dynamic Payloads},
  booktitle = {Proc. of the 11th International Symposium on Experimental Robotics (ISER)},
  year = {2008},
  url = {http://iuliu.com/pub/ISER08%20Buoyancy.pdf}
}

We describe the design, implementation and programming of a set of robots that, starting from an amorphous arrangement, can be assembled into arbitrary shapes and then commanded to self-disassemble in an organized manner to obtain a goal shape. We present custom hardware, distributed algorithms and experimental results from hundreds of trails which show the system successfully forming complex 3D shapes. Each of the 28 modules in the system is implemented as a 1.8-inch autonomous cube-shaped robot able to connect to and communicate with its immediate neighbors. Embedded microprocessors control each module's magnetic connection mechanisms and infrared communication interfaces. When assembled into a structure, the modules form a system that can be virtually sculpted using a computer interface and a distributed process. The group of modules collectively decides which elements are a part of the final shape and which are not using algorithms that minimize information transmission and storage. Finally, the modules not in the structure disengage their magnetic couplings and fall away under the influence of an external force: in this case, gravity.

@article{iuliu-ijrr08,
  author = {Gilpin, Kyle and Kotay, Keith and Rus, Daniela and Vasilescu, Iuliu},
  title = {Miche: Modular Shape Formation by Self-Disassembly},
  journal = {The International Journal of Robotics Research},
  publisher = {Sage Publications, Inc.},
  year = {2008},
  volume = {27},
  number = {3-4},
  pages = {345--372},
  url = {http://iuliu.com/pub/IJRR08%20Miche%20self%20dissasembly.pdf},
  doi = {http://dx.doi.org/10.1177/0278364907085557}
}

A distributed model structure for representing groups of coupled dynamic agents is proposed, and the least-squares method is used for fitting model parameters based on measured position data. The difference equation model embodies a minimalist approach, incorporating only factors essential to the movement and interaction of physical bodies. The model combines effects from an agent’s inertia, interactions between agents, and interactions between each agent and its environment. Global positioning system tracking data were collected in field experiments from a group of 3 cows and a group of 10 cows over the course of several days using custom-designed, head-mounted sensor boxes. These data are used with the least-squares method to fit the model to the cow groups. The modeling technique is shown to capture overall characteristics of the group as well as attributes of individual group members. Applications to livestock management are described, and the potential for surveillance, prediction, and control of various kinds of groups of dynamic agents are suggested.

@article{iuliu-jfr08,
  author = {Mac Schwager and Carrick Detweiler and Iuliu Vasilescu and Dean M. Anderson and Daniela Rus},
  title = {Data-Driven Identification of Group Dynamics for Motion Prediction and Control},
  journal = {Journal of Field Robotics},
  year = {2008},
  volume = {25},
  number = {6-7},
  pages = {305-324},
  url = {http://iuliu.com/pub/JFR08%20Data%20Driven%20Identification%20of%20Group%20Dynamics.pdf}
}

This paper describes a novel experiment in which two very different methods of underwater robot localization are compared. The first method is based on a geometric approach in which a mobile node moves within a field of static nodes, and all nodes are capable of estimating the range to their neighbours acoustically. The second method uses visual odometry, from stereo cameras, by integrating scaled optical flow. The fundamental algorithmic principles of each localization technique is described. We also present experimental results comparing acoustic localization with GPS for surface operation, and a comparison of acoustic and visual methods for underwater operation.

@inproceedings{iuliu-icra07,
  author = {Corke, Peter and Detweiler, Carrick and Dunbabin, Mathew and Hamilton, Michael and Rus, Daniela and Vasilescu, Iuliu},
  title = {Experiments with Underwater Robot Localization and Tracking},
  booktitle = {Proc. of IEEE International Conference on Robotics and Automation (ICRA)},
  year = {2007},
  pages = {4556-4561},
  url = {http://iuliu.com/pub/ICRA07%20Experiments%20with%20Underwater%20Robot%20Localization%20and%20Tracking.pdf},
  doi = {http://dx.doi.org/10.1109/ROBOT.2007.364181}
}

This paper describes an underwater sensor network with dual communication and support for sensing and mobility. The nodes in the system are connected acoustically for broadcast communication using an acoustic modem we developed. The nodes are connected optically for higher speed point to point data transfers using an optical modem we developed. We describe the hardware details of the underwater sensor node and the communication and networking protocols. Finally, we present and discuss the results from experiments with this system.

@inproceedings{iuliu-oceans07,
  author = {Detweiller, Carrick and Vasilescu, Iuliu and Rus, Daniela},
  title = {An Underwater Sensor Network with Dual Communications, Sensing, and Mobility},
  booktitle = {OCEANS Europe},
  year = {2007},
  pages = {1-6},
  url = {http://iuliu.com/pub/OCEANS07%20UWSN%20with%20dual%20communications,%20sensing%20and%20mobility.pdf},
  doi = {http://dx.doi.org/10.1109/OCEANSE.2007.4302445}
}

This paper describes an underwater sensor network with dual communication and support for sensing and mobility.<br>The nodes in the system are connected acoustically for broadcast communication using an acoustic modem we developed. For higher point to point communication speed the nodes are networked optically using custom built optical modems. We describe the hardware details of the underwater sensor node and the communication and networking protocols. Finally, we present and discuss the results from experiments with this system.

@inproceedings{iuliu-wuwnet07,
  author = {Iuliu Vasilescu and Carrick Detweiler and Daniela Rus},
  title = {AquaNodes: An Underwater Sensor Network},
  booktitle = {WuWNet},
  year = {2007},
  url = {http://iuliu.com/pub/WUWNETS07%20Aquanodes.PDF}
}

We present algorithms, systems, and experimental results for underwater data muling. In data muling a mobile agent interacts with static agents to upload, download, or transport data to a different physical location. We consider a system comprising an Autonomous Underwater Vehicle (AUV) and many static Underwater Sensor Nodes (USN) networked together optically and acoustically. The AUV can locate the static nodes using vision and hover above the static nodes for data upload. We describe the hardware and software architecture of this underwater system, as well as experimental data.

@inproceedings{iuliu-icra06,
  author = { Dunbabin, Mathew and Corke, Peter and Vasilescu, Iuliu and Rus, Daniela},
  title = {Data muling over underwater wireless sensor networks using an autonomous underwater vehicle},
  booktitle = {Proc. of IEEE International Conference on Robotics and Automation (ICRA)},
  year = {2006},
  pages = { 2091-2098},
  url = {http://iuliu.com/pub/ICRA06%20Data%20Muling%20over%20UWSN%20using%20an%20Autonomous%20Underwater%20Vehicle.pdf}
}

We present details and results obtained with an underwater system comprising two different autonomous underwater robots (AUV) and ten static underwater nodes (USN) networked together optically and acoustically. The AUVs can locate and hover above the static nodes for data upload, and they can perform network maintenance functions such as deployment, relocation, and recovery. The AUVs can also locate each other, dock, and move using coordinated control that takes advantage of each AUV’s strength.

@inproceedings{iuliu-iser06,
  author = {Matthew Dunbabin and Iuliu Vasilescu and Peter I. Corke and Daniela Rus},
  title = {Experiments with Cooperative Networked Control of Underwater Robots},
  booktitle = {Proc. of The 10th International Symposium on Experimental Robotics (ISER)},
  year = {2006},
  pages = {463-470},
  url = {http://iuliu.com/pub/ISER06%20Cooperative.pdf}
}

We present the design, analysis and construction of a biologicallyinspired tactile sensor. The sensor can measure normal and lateralforces, conform to the surfaces with which it comes in contact andincrease the friction of the surface for a good grasp.The sensor is built using a simple process and the applied forcesare read using standard electronics. These features make thesensors ideal for mass production.We are motivated to build tactile sensors that are useful forrobotic manipulation given that the current ones do not have thefeatures that we consider necessary. The sensors presented in thispaper have been designed to deal with these issues. They have beendesigned and implemented in the fingers of the humanoid robot Obrero.

@techreport{iuliu-csail06,
  author = {Torres-Jara, Eduardo and Vasilescu, Iuliu and Coral, Raul},
  title = {A soft touch: Compliant Tactile Sensors for Sensitive Manipulation},
  year = {2006},
  url = {http://iuliu.com/pub/TR06%20soft%20touch.pdf}
}

We consider the optimization problem of safety stock placement in a supply chain, as formulated in [1]. We prove that this problem is NP-Hard for supply chains modeled as general acyclic networks. Thus, we do not expect to find a polynomial-time algorithm for safety stock placement for a general-network supply chain.

@inproceedings{iuliu-imst05,
  author = {Ekaterina Lesnaia and Iuliu Vasilescu and Stephen C. Graves},
  title = {The Complexity of Safety Stock Placement in General-Network Supply Chains},
  booktitle = {Innovation in Manufacturing Systems and Technology},
  year = {2005},
  url = {http://iuliu.com/pub/IMST05%20Complexity%20of%20Safety%20Stocks.pdf}
}

In this paper we present a novel platform for underwater sensor networks to be used for long-term monitoring of coral reefs and fisheries. The sensor network consists of static and mobile underwater sensor nodes. The nodes communicate point-to-point using a novel high-speed optical communication system integrated into the TinyOS stack, and they broadcast using an acoustic protocol integrated in the TinyOS stack. The nodes have a variety of sensing capabilities, including cameras, water temperature, and pressure. The mobile nodes can locate and hover above the static nodes for data muling, and they can perform network maintenance functions such as deployment, relocation, and recovery. In this paper we describe the hardware and software architecture of this underwater sensor network. We then describe the optical and acoustic networking protocols and present experimental networking and data collected in a pool, in rivers, and in the ocean. Finally, we describe our experiments with mobility for data muling in this network.

@inproceedings{iuliu-sensys05,
  author = {Vasilescu, Iuliu and Kotay, Kotay and Rus, Daniela and Dunbabin, Mathew and Corke, Peter},
  title = {Data collection, storage, and retrieval with an underwater sensor network},
  booktitle = {Proceedings of the 3rd international conference on Embedded networked sensor systems (SenSys)},
  publisher = {ACM},
  year = {2005},
  pages = {154--165},
  url = {http://iuliu.com/pub/SENSYS06%20Data%20Collection%20Storage%20and%20Retrieval%20with%20UWSN.PDF},
  doi = {http://doi.acm.org/10.1145/1098918.1098936}
}

While sensor networks have now become very popular on land, the underwater environment still poses some difficult problems. Communication is one of the difficult challenges underwater. There are two options: optical and acoustic. We have designed an optical communication board that allows the Fleck’s to communicate optically. We have tested the resulting underwater sensor nodes in two different applications.

@inproceedings{iuliu-emnets05,
  author = {Vasilescu, Iuliu and Kotay, Keith and Rus, Daniela and Overs, Leslie and Sikka, Pavan and Dunbabin, Mathew and Chen, P and Corke, Peter},
  title = {Krill: An Exploration in Underwater Sensor Networks},
  booktitle = {Proc. of The Second IEEE Workshop Embedded Networked Sensors. (EmNetS-II)},
  year = {2005},
  pages = {151-152},
  url = {http://iuliu.com/pub/EMNETS05%20KRILL,%20An%20Exploration%20in%20USN.pdf}
}

We propose a novel modular underwater robot which can self-reconfigure by stacking and unstacking its component modules. Applications for this robot include underwater monitoring, exploration, and surveillance. Our current prototype is a single module which contains several subsystems that later will be segregated into different modules. This robot functions as a testbed for the subsystems which are needed in the modular implementation. We describe the module design and discuss the propulsion, docking, and optical ranging subsystems in detail. Experimental results demonstrate depth control, linear motion, target module detection, and docking capabilities.

@inproceedings{iuliu-icra05,
  author = {Vasilescu, Iuliu and Varshavskaya, Paulina and Kotay, Keith and Rus, Daniela},
  title = {Autonomous Modular Optical Underwater Robot (AMOUR) Design, Prototype and Feasibility Study},
  booktitle = {Proc. of IEEE International Conference on Robotics and Automation (ICRA)},
  year = {2005},
  pages = { 1603-1609},
  url = {http://iuliu.com/pub/ICRA05%20Autonomous%20Optical%20Modular%20Underwater%20Robot%20(AMOUR).pdf}
}