Autonomous underwater vehicles in a hazardous non-deterministic environment

This research investigated the cooperation of multi underwater robots to perform a task. This combined engineering design, electronics and consensus control to create systems capable of achieving the task. Challenges such as underwater radio communications were researched and a simulation framework was created and tested on virtual and real systems.

Distributed protocol for communications among underwater vehicles

Underwater surveying by swarms of autonomous underwater vehicles presents problems in communication among the robots. These problems involve the bandwidth, power consumption, timing, processing power, and other issues. This paper presents a novel approach to communicate and coordinate effectively among underwater vehicles to accomplish this task successfully. The proposed approach solves issues by reducing the number of hops to conserve power, while reducing computation time and bandwidth, effectively utilizing resources to reduce the load on each node. Finally, the simulation results are presented, in order to prove that the proposed approach improves efficiency and effectiveness in communicating among underwater vehicles.

Design and analysis of hull configurations for a low-cost, autonomous underwater robot as an enabling technology for system of system applications

The objective of this research is to model and analyze candidate hull configurations for a low-cost, modular, autonomous underwater robot. As the computational power and speed of microprocessors continue to progress, we are seeing a growth in the research, development, and the utilization of underwater robots. The number of applications is broadening in the R&D and science communities, especially in the area of multiple, collaborative robots. These underwater collaborative robots represent an instantiation of a System of Systems (SoS). While each new researcher explores a unique application, control method, etc. a new underwater robot vehicle is designed, developed, and deployed. This sometimes leads to one-off designs that are costly. One limit to the wide-scale utilization of underwater robotics is the cost of development. Another limit is the ability to modify the configuration for new applications and evolving requirements. Consequently, we are exploring autonomous underwater vehicle (AUV) hull designs towards the goal of modularity, vehicle dexterity, and minimizing the cost. In our analysis, we have employed 3D solid modeling tools and finite element methods. In this paper we present our initial results and discuss ongoing work.

Communications for underwater robotics research platforms

This paper presents a distributed protocol for communication among autonomous underwater vehicles. It is a complementary approach for coordination between the autonomous underwater vehicles. This paper mainly describes different methods for underwater communication. One of the methods is brute force approach in which messages are broadcasted to all the communication nodes, which in turn will broadcast the acknowledgement. Issues relating to this brute force approach are time delay, number of hops, power consumption, message collision and other practical issues. These issues are discussed and solved by proposing a new method to improve efficiency of this proposed approach and its effectiveness in communication among autonomous underwater vehicles.

Adaptive robust control of 6-DOF autonomous aerial vehicles

The thesis focused on development of an auto-pilot system for UAV’s and small fixed wing aircraft for use in hazardous flight conditions, such as severe weather. This led to development of a mathematical algorithm that unbinds the flight systems from coupling effects which can adaptively changed to the environment.

Predictive motion planning for AUVs subject to strong time-varying currents and forecasting uncertainties

This paper presents a novel path planning method for minimizing the energy consumption of an autonomous underwater vehicle subjected to time varying ocean disturbances and forecast model uncertainty. The algorithm determines 4-Dimensional path candidates using Nonlinear Robust Model Predictive Control (NRMPC) and solutions optimised using A∗-like algorithms. Vehicle performance limits are incorporated into the algorithm with disturbances represented as spatial and temporally varying ocean currents with a bounded uncertainty in their predictions. The proposed algorithm is demonstrated through simulations using a 4-Dimensional, spatially distributed time-series predictive ocean current model. Results show the combined NRMPC and A∗ approach is capable of generating energy-efficient paths which are resistant to both dynamic disturbances and ocean model uncertainty.

Design of a low cost underwater robotic research platform

To perform under water robotic research requires specialized equipment. A few pieces of electronics atop a set of wheels is not going to cut it. An underwater research platform must be waterproof, reliable, robust, recoverable and easy to maintain. It must also be able to move in 3 dimensions. Finally it must be able to navigate and avoid obstacles. To purchase such a platform can be very expensive. However, for shallow water, a suitable platform can be built from mostly off the shelf items at little cost. This paper describes the design of one such underwater robot including various sensors and communications systems that allow for swarm robotics.

Simulation of underwater robots using MS Robot Studio©

One stage in designing the control for underwater robot swarms is to confirm the control algorithms via simulation. To perform the simulation Microsoftpsilas Robotic Studiocopy was chosen. The problem with this simulator and others like it is that it is set up for land-based robots only. This paper explores one possible way to get around this limitation. This solution cannot only work for underwater vehicles but aerial vehicles as well.

Consensus control for a system of underwater swarm robots

The control of a swarm of underwater robots requires both a control algorithm and a communication system. Unfortunately, underwater communications is difficult at the best of times and so large time delays and minimal information is a concern. The control system must be able to handle a large number of robots without a master control, i.e., a decentralized control approach. This paper describes Consensus control as a way to decentralize. Consensus control allows each robot to know the final goal and then to decide, based on the position of the other robots, its best move to help achieve the goal.

Design of a prototype underwater research platform for swarm robotics

To perform under water robotic research requires specialized equipment. A few pieces of electronics atop a set of wheels are not going to cut it. An underwater research platform must be waterproof, reliable, robust, recoverable and easy to maintain. It must also be able to move in 3 dimensions. Also it must be able to navigate and avoid obstacles. Further if this platform is to be part of a swarm of like platforms then it must be cost effective and relatively small. To purchase such a platform can be very expensive. However, for shallow water, a suitable platform can be built from mostly off the shelf items at little cost. This article describes the design of one such underwater robot including various sensors and communications systems that allow for swarm robotics. Whilst the robotic platform performs well, to explore what many of them would do, that is more than are available, simulation is required. This article continues to study how best to simulate these robots for a swarm, or system of systems, approach.

Underwater swarm robotics consensus control

The control of a swarm of underwater robots requires more than just a control algorithm, it requires a communications system. Underwater communications is difficult at the best of times and so large time delays and minimal information is a concern. The control system must be able to work on minimal and out of date information. The control system must also be able to control a large number of robots without a master control, a decentralized control approach. This paper describes one such control method.

Adaptive fuzzy multi-surface sliding control of multiple-input and multiple-output autonomous flight systems

In this study, we proposed an adaptive fuzzy multi-surface sliding control (AFMSSC) for trajectory tracking of 6 degrees of freedom inertia coupled aerial vehicles with multiple inputs and multiple outputs (MIMO). It is shown that an adaptive fuzzy logic-based function approximator can be used to estimate the system uncertainties and an iterative multi-surface sliding control design can be carried out to control flight. Using AFMSSC on MIMO autonomous flight systems creates confluent control that can account for both matched and mismatched uncertainties, system disturbances and excitation in internal dynamics. It is proved that the AFMSSC system guarantees asymptotic output tracking and ultimate uniform boundedness of the tracking error. Simulation results are presented to validate the analysis.

Applications and prototype for systems of systems swarm robotics

In order to develop a robotic system of systems the robotic platforms must be designed and built. For this to happen, the type of application involved should be clear. Swarm robots need to be self contained and powered. They must also be self governing. Here the authors examine various applications and a prototype robot that may be useful in these scenarios.

Design of an angular radial robotic stingray

The propeller is the primary propulsion method for underwater vehicles. It is relatively simple to implement and generally uses rotational motion from the drive through to the propeller. However, it is difficult to seal a high speed propeller shaft from water ingress. As an alternative we can look at nature's own underwater inhabitants and study their locomotive methods.

Outcropping reef ledges drive patterns of epibenthic assemblage diversity on cross-shelf habitats

Seafloor habitats on continental shelf margins are increasingly being the subject of worldwide conservation efforts to protect them from human activities due to their biological and economic value. Quantitative data on the epibenthic taxa which contributes to the biodiversity value of these continental shelf margins is vital for the effectiveness of these efforts, especially at the spatial resolution required to effectively manage theseecosystems. We quantified the diversity of morphotype classes on an outcropping reef system characteristic of the continental shelf margin in the Flinders Commonwealth Marine Reserve, southeastern Australia. The system is uniquely characterized by long linear outcropping ledge features in sedimentary bedrock that differ markedly from the surrounding low-profile, sand-inundated reefs. We characterize a reef system harboring rich morphotype classes, with a total of 55 morphotype classes identified from the still images captured by an autonomous underwater vehicle. The morphotype class Cnidaria/Bryzoa/Hydroid matrix dominated the assemblages recorded. Both a and b diversitydeclined sharply with distance from nearest outcropping reef ledge feature. Patterns of the morphotype classes were characterized by (1) morphotype turnover at scales of 5 to 10s m from nearest outcropping reef ledge feature, (2) 30 % of morphotype classes were recordedonly once (i.e. singletons), and (3) generally low levels of abundance (proportion cover) of the component morphotype class. This suggests that the assemblages in this region contain a considerable number of locally rare morphotype classes. This study highlights the particular importance of outcropping reef ledge features in this region, as they provide a refuge against sediment scouring and inundation common on the low profile reef that characterizes this region. As outcropping reef features, they represent a small fraction of overall reef habitat yet contain much of the epibenthic faunal diversity. This study has relevance to conservation planning for continental shelf habitats, as protecting a single, or few, areas of reef is unlikely to accurately represent the geomorphic diversity of cross-shelf habitats and the morphotype diversity that is associated with these features. Equally, whendesigning monitoring programs these spatially-discrete, but biologically rich outcropping reef ledge features should be considered as distinct components in stratified sampling designs.