Christopher Kitts

Cluster Space Specification and Control of Mobile Multirobot Systems

The cluster space state representation of mobile multirobot systems is introduced as a means of enabling enhanced control of mobile multirobot systems. A conceptual framework is proposed for the selection of appropriate cluster space state variables for an n-robot system, the development of formal kinematics that associate the cluster space state variables with robot-specific variables, and the implementation of a cluster space control system architecture. The cluster space approach is then demonstrated for examples of two- and three-robot clusters consisting of differential drive robots operating in a plane. In these examples, we demonstrate cluster space variable selection, review the critical kinematic relationships, and present experimental results that demonstrate the ability of the systems to meet control specifications while allowing a single operator to easily specify and supervise the motion of the clusters.

Entrapment/escorting and patrolling missions in multi-robot cluster space control

The tasks of entrapping/escorting and patrolling around an autonomous target are presented making use of the multi-robot cluster space control approach. The cluster space control technique promotes simplified specification and monitoring of the motion of mobile multi-robot systems of limited size. Previous work has established the conceptual foundation of this approach and has experimentally verified and validated its use for 2-robot, 3-robot and 4-robot systems, with varying implementations ranging from automated trajectory control to human-in-the-loop piloting. In this publication, we show that the problem of entrapping/escorting/patrolling is trivial to define and manage from a cluster space perspective. Using a 3-robot experimental testbed, results are shown for the given tasks. We also revise the definition of the cluster space framework for a three-robot formation and incorporate a robot-level obstacle avoidance functionality.

The O/OREOS Mission: First Science Data from the Space Environment Survivability of Living Organisms (SESLO) Payload

We report the first telemetered spaceflight science results from the orbiting Space Environment Survivability of Living Organisms (SESLO) experiment, executed by one of the two 10 cm cube-format payloads aboard the 5.5 kg Organism/Organic Exposure to Orbital Stresses (O/OREOS) free-flying nanosatellite. The O/OREOS spacecraft was launched successfully to a 72° inclination, 650 km Earth orbit on 19 November 2010. This satellite provides access to the radiation environment of space in relatively weak regions of Earths protective magnetosphere as it passes close to the north and south magnetic poles; the total dose rate is about 15 times that in the orbit of the International Space Station. The SESLO experiment measures the long-term survival, germination, and growth responses, including metabolic activity, of Bacillus subtilis spores exposed to the microgravity, ionizing radiation, and heavy-ion bombardment of its high-inclination orbit. Six microwells containing wild-type (168) and six more containing radiation-sensitive mutant (WN1087) strains of dried B. subtilis spores were rehydrated with nutrient medium after 14 days in space to allow the spores to germinate and grow. Similarly, the same distribution of organisms in a different set of microwells was rehydrated with nutrient medium after 97 days in space. The nutrient medium included the redox dye Alamar blue, which changes color in response to cellular metabolic activity. Three-color transmitted intensity measurements of all microwells were telemetered to Earth within days of each of the 48 h growth experiments. We report here on the evaluation and interpretation of these spaceflight data in comparison to delayed-synchronous laboratory ground control experiments.

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.

Obstacle Avoidance Policies for Cluster Space Control of Nonholonomic Multirobot Systems

The cluster space control technique promotes simplified specification and monitoring of the motion of mobile multirobot systems of limited size. In this publication, we summarize the definition of the cluster space framework and introduce a multirobot cluster space controller specific for unicycle-like nonholonomic mobile robots. The controller produces cluster commands that translate into valid robot-level motions. We then study the closed-loop system stability in the Lyapunov sense. Two different obstacle avoidance algorithms are proposed and the stability of the resulting systems is also addressed. Experimental tests with a three-robot system and simulation results with a ten-robot system verify the functionality of the proposed approaches.

Cluster space specification and control of a 3-robot mobile system

The cluster space control technique promotes simplified specification and monitoring of the motion of mobile multi-robot systems of limited size. Previous work has established the conceptual foundation of this approach and has experimentally verified and validated its use for two diverse 2- robot systems and with varying implementations ranging from automated trajectory control to human-in-the-loop piloting. In this paper, we present the cluster space control of a 3-robot system. In doing so, we develop the fundamental kinematic relationships, illustrate the closed-loop control framework, describe the simulation and hardware testbed environments used for verification, and present initial experimental results of the successfully implemented 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.

Self-Positioning Smart Buoys, The "Un-Buoy" Solution: Logistic Considerations using Autonomous Surface Craft Technology and Improved Communications Infrastructure

Moored buoys have long served national interests, but incur high development, construction, installation, and maintenance costs. Buoys which drift off-location can pose hazards to mariners, and in coastal waters may cause environmental damage. Moreover, retrieval, repair and replacement of drifting buoys may be delayed when data would be most useful. Such gaps in coastal buoy data can pose a threat to national security by reducing maritime domain awareness. The concept of self-positioning buoys has been advanced to reduce installation cost by eliminating mooring hardware. We here describe technology for operation of reduced cost self-positioning buoys which can be used in coastal or oceanic waters. The ASC SCOUT model is based on a self-propelled, GPS-positioned, autonomous surface craft that can be pre-programmed, autonomous, or directed in real time. Each vessel can communicate wirelessly with deployment vessels and other similar buoys directly or via satellite. Engineering options for short or longer term power requirements are considered, in addition to future options for improved energy delivery systems. Methods of reducing buoy drift and position-maintaining energy requirements for self-locating buoys are also discussed, based on the potential of incorporating traditional maritime solutions to these problems. We here include discussion of the advanced Delay Tolerant Networking (DTN) communications draft protocol which offers improved wireless communication capabilities underwater, to adjacent vessels, and to satellites. DTN is particularly adapted for noisy or loss-prone environments, thus it improves reliability. In addition to existing buoy communication via commercial satellites, a growing network of small satellites known as PICOSATs can be readily adapted to provide low-cost communications nodes for buoys. Coordination with planned vessel Automated Identification Systems (AIS) and International Maritime Organization standards for buoy and vessel notification systems are reviewed and the legal framework for deployment of autonomous surface vessels is considered

A behavioral control approach to formation-keeping through an obstacle field

This work addresses the problem of guiding a number of ground vehicles from some initial location to a specified destination, while avoiding obstacles in an unmapped field and maintaining formation relative to each other. Potential applications for recently developed ground formation are described in this paper, illustrating the need for autonomy in such formation systems. The behavior-base technique has been implemented to reach this autonomy in differential drive kinematics systems. The basic behaviors: move-to-goal, avoid-obstacle, maintain-relative-distance, maintain-relative-angle, and stop have been assigned to the independent systems to form a guidance algorithm. Validation of this guidance algorithm is carried out through simulations via Matlab/Simulink.

Surf, turf, and above the Earth [robotics education]

The Santa Clara University School of Engineering conducts a low-cost, aggressive, integrative educational program focused on developing intelligent robotic systems. The centerpiece of this program is a set of yearly undergraduate design projects in which teams of senior students completely design, fabricate, test, operate, and manage high quality robotic systems. These systems include spacecraft, underwater vehicles, terrestrial rovers, airships, telescopes, and industrial robots.