Paul Mahacek

Dynamic Guarding of Marine Assets Through Cluster Control of Automated Surface Vessel Fleets

There is often a need to mark or patrol marine areas in order to prevent boat traffic from approaching critical regions, such as the location of a high-value vessel, a dive site, or a fragile marine ecosystem. In this paper, we describe the use of a fleet of robotic kayaks that provides such a function: the fleet circum- navigates the critical area until a threatening boat approaches, at which point the fleet establishes a barrier between the ship and the protected area. Coordinated formation control of the fleet is implemented through the use of the cluster-space control architecture, which is a full-order controller that treats the fleet as a virtual, articulating, kinematic mechanism. An application-specific layer interacts with the cluster-space controller in order for an operator to directly specify and monitor guarding-related parameters, such as the spacing between boats. This system has been experimentally verified in the field with a fleet of robotic kayaks. In this paper, we describe the control architecture used to establish the guarding behavior, review the design of the robotic kayaks, and present experimental data regarding the functionality and performance of the system.

Field operation of a robotic small waterplane area twin hull boat for shallow-water bathymetric characterization

An innovative robotic boat has been developed for performing bathymetric mapping of very shallow coastal, estuarine, and inland waters. The boat uses a small waterplane area twin hull design to provide natural platform stability for a multibeam sonar payload, and a navigation system automatically guides the boat in a “lawn-mowing” pattern to map a region of interest. Developed in stages over five years as part of a low-cost student design program, the boat is now operational and is being used to generate science-quality maps for scientific and civil use; it is also being used as a testbed for evaluating the platform for other types of scientific missions and for demonstrating advanced control techniques. This paper reviews the student-based development process, describes the design of the boat, presents results from field operations, and reviews plans for future extensions to the system.

Cluster Space Control of Autonomous Surface Vessels

Flexibility, coverage, and redundancy are only three of the many advantages that multi-robot systems offer over single-robot systems. Individual unit coordination is a key technical consideration in fielding real-world application multi-robot systems. Simplified mobile multi-robot system motion specification and monitoring are promoted through the cluster space control technique. This approach has been established and experimentally verified in previous work for use with varying implementations ranging from human-in-the-loop piloting to automated trajectory control and for land-based systems consisting of 2-4 robots. A new low-cost autonomous surface vessels (ASVs) design and fabrication is described by the authors in this paper. A multi-boat system that uses the cluster space control technique to make it capable of autonomous navigation is included in the technical system. A centralized controller is also included that uses a shore-based computer to relay drive commands and receive ASV data in its implementation. A pilot may specify that a third boat maintain formation with two ASVs or may remotely drive a two-ASV cluster by using these drive commands when using the cluster space control approach. Depending on the needs of a specific application, there can be arbitrary translation, rotation, and resizing of the resulting multi-ASV clusters. There is discussion of plans for future works and provision of experimental results demonstrating these capabilities.

SeaWASP: A Small Waterplane Area Twin Hull Autonomous Platform for Shallow Water Mapping

Students with Santa Clara University (SCU) and the Monterey Bay Aquarium Research Institute (MBARI) are developing an innovative platform for shallow water bathymetry. Bathymetry data is used to analyze the geography, ecosystem, and health of marine habitats. However, current methods for shallow water measurements typically involve large, manned vessels. These vessels may pose a danger to themselves and the environment in shallow, semi-navigable waters. Small vessels, however, are prone to disturbance by the waves, tides, and currents of shallow water. The SCU / MBARI autonomous surface vessel (ASV) is designed to operate safely, stably in waters > 1 m and without significant manned support. Final deployment will be at NOAAs Kasitsna Bay Laboratory in Alaska. The ASV utilizes several key design components to provide stability, shallow draft, and long-duration unmanned operations. Bathymetry is measured with a multibeam sonar in concert with DVL and GPS sensors. Pitch, roll, and heave are minimized by a Small Waterplane Area Twin Hull (SWATH) design. The SWATH has a submerged hull, small water-plane area, and high mass to damping ratio, making it less prone to disturbance and ideal for accurate data collection. Precision sensing and actuation is controlled by onboard autonomous algorithms. Autonomous navigation increases the quality of the data collection and reduces the necessity for continuous manning. The vessel has been operated successfully in several open water test environments, including Elkhorn Slough, CA, Stevens Creek, CA, and Lake Tahoe, NV. It is currently is in the final stages of integration and test for its first major science mission at Orcas Island, San Juan Islands, WA, in August, 2008. The Orcas Island deployment will feature design upgrades implemented in Summer, 2008, including additional batteries for all-day power (minimum eight hours), active ballast, real-time data monitoring, updated autonomous control electronics and software, and data editing using in-house bathymetry mapping software, MB-System. This paper will present the results of the Orcas Island mission and evaluate possible design changes for Alaska. Also, we will include a discussion of our shallow water bathymetry design considerations and a technical overview of the subsystems and previous test results. The ASV has been developed in partnership with Santa Clara University, the Monterey Bay Aquarium Research Institute, the University of Alaska Fairbanks, and NOAAs West Coat and Polar Regions Undersea Research Center.

Development and initial testing of a SWATH boat for shallow-water bathymetry

Students at Santa Clara University have developed a SWATH boat prototype capable of shallow water operation and configured for creating bathymetric maps through the use of a multi-beam sonar. The sonar works in concert with DVL and precision GPS sensors in order to log data that can be used to generate bathymetric maps through the use of the MB System software suite. The boats physical structure includes pontoons, vertical supports, and a platform housing the vessels power, sensor, control, and communication systems. Additional systems include a camera and video transmission system for remotely piloted operation, a suite of sensors and controllers for autonomous navigation, and equipment for ballasting the pontoons. An off-board control station aids in navigation computations, provides the pilot/supervisor interface, and links the system to the internet for real-time internet-based piloting and/or monitoring of the mission. An additional winch system has been developed for future operations involving the deployment of a sensor package to various depths. A number of successful test deployments have been completed to date, and operations during the summer of 2008 will include mapping of the Elkhorn Slough, portions of the southern end of San Francisco Bay, portions of Lake Tahoe, and shallow water coastal waters in the San Juan Islands. Ultimately, a more robust model of the boat is planned for deployment at NOAAs Kasitsna Bay Laboratory in Alaska. The system has been developed in partnership with the Monterey Bay Aquarium Research Institute, the University of Alaska Fairbanks, and NOAAs West Coast and Polar Regions Undersea Research Center. This paper will review the technical design of the system and will present the functional performance achieved to date.

Cluster space control of a 2-robot system as applied to Autonomous Surface Vessels

Multi-robot systems offer many advantages over a single robot system including redundancy, coverage and flexibility. One of the key technical considerations in fielding multi-robot systems for real-world applications is the coordination of the individual units. The cluster space control technique promotes simplified specification and monitoring of the motion of mobile multi-robot systems. Previous work has established this approach and has experimentally verified its use for land based systems consisting of 2-4 robots and with varying implementations ranging from automated trajectory control to human-in-the-loop piloting. In this paper, we describe a multi-boat system capable of autonomous navigation using the cluster space control technique. The technical system includes the design and fabrication of a new low cost autonomous surface vessel (ASV). It also includes a centralized controller, currently implemented via a shore-based computer, that wireless receives ASV data and relays drive commands. Using the cluster space control approach, these drive commands allow a pilot to remotely drive a 2-boat cluster or two boats to automatically maintain formation with a third boat. The resulting multi-ASV clusters can be arbitrarily translated, rotated, and resized depending upon the needs of a specific application. Experimental results demonstrating these capabilities will be provided, and plans for future work will be discussed.

Cluster space control of autonomous surface vessels utilizing obstacle avoidance and shielding techniques

Multi-robot systems offer many advantages over a single robot system including redundancy, coverage and flexibility. One of the key technical challenges in fielding multi-robot systems for real-world applications is the coordination and relative motion control of the individual units. The cluster space control technique addresses the motion control challenge by providing formation control and promoting the simplified specification and monitoring of the motion of mobile multi-robot systems. Previous work has established this approach and has experimentally verified its use for dynamic marine surface vessels consisting of 2 or 3 robots and with varying implementations ranging from automated cluster trajectory control to human-in-the-loop piloting. In this research program, we apply the cluster space control technique to a larger group of marine vessels and include both obstacle avoidance and threat detection with shielding formations. The resulting system is capable of autonomous navigation utilizing a centralized controller, currently implemented via a shore-based computer, that wirelessly receives ASV data and relays control commands. Using the cluster space control approach, these control commands allow a cluster supervisor to oversee a flexible and mobile perimeter formed by the ASV cluster or to detect a threat and establish a shield between the operation and the threat. Theoretical formulation and simulation results demonstrating these capabilities are provided, and plans for future work are discussed.

Responsive Small Satellite Mission Operations Using An Enterprise-Class Internet-Based Command and Control Network

Rapid integration of spacecraft into low-cost mission control systems is an essential element of enabling cost-effective, responsive space missions. This paper describes a distributed satellite ground segment and control network that is developed and operated by students at Santa Clara University in order to support a wide variety of NASA and university-class small spacecraft. In addition to reviewing the technical design of the system and summarizing the missions being supported, the paper outlines several strategies for implementing a low-cost system that supports rapid integration of new spacecraft.

The WASP: an atonomous surface vessel for the University of Alaska

The vision of the autonomous surface vessel program is to develop an instrumented boat capable of robust, automatic sampling of oceanographic data at specific locations and depths in estuary and coastal waters. The objective of the WASP project was to develop an initial prototype of such a system including software, physical hardware and electronic components. The physical structure includes pontoons, vertical supports, and a platform housing the vessels power source, onboard electronics and payload. The onboard electronics control the movement and functionality of the vessel and the payload of scientific instruments are attached to a winch for taking readings at depth. Also, the user interface developed for the wireless communication and control of the vessel is Internet based allowing the user to control the vessel anywhere in the world. This prototype will be integrated and tested in Elkhorn Slough during the summer of 2005 as part of an SCU-MBARI project. The work performed to date has been critical in the development of the ASV concept which is expected to lead to an operational system deployed in the Kasitsna Bay Laboratory in Alaska and other national estuaries.

Experiments in the control and application of Automated Surface Vessel fleets

Over the past two decades, the use of Automated Surface Vessels (ASVs) has evolved from serving as military drones to performing a rich set of applications ranging from exploration to minesweeping to supporting the operation of underwater assets. The benefits of these systems motivate the question of how fleets of such ASVs could synergistically work together to perform more sophisticated and challenging tasks. In this paper, we describe our recent work in exploring the use of multi-ASV systems that sail in controlled formations in order to perform specific niche applications. We first describe our cluster space control technique, a formation control approach that promotes simple specification and monitoring of multi-robot systems. We then describe the design of our simple robotic kayaks which serve as our testbed for multi-ASV applications. Next, we show how we have applied the cluster space control to the multi-kayak fleet in order to test application concepts such as escorting/patrolling and gradient-based adaptive environmental sampling. Finally, we briefly describe some of our ongoing extensions to this work.