D. P. Horner

AUV Control and Communication using Underwater Acoustic Networks

Underwater acoustic networks can be quite effective to establish communication links between autonomous underwater vehicles (AUVs) and other vehicles or control units, enabling complex vehicle applications and control scenarios. A communications and control framework to support the use of underwater acoustic networks and sample application scenarios are described for single and multi-AUV operation.

AUV experiments in obstacle avoidance

Reactive obstacle avoidance (OA) is an important step in attaining greater autonomy in autonomous underwater vehicles (AUV). For AUVs that conduct underwater surveys, avoidance of uncharted obstacles can improve vehicle survivability. This paper discusses initial experiments at the Center for AUV Research in obstacle detection and avoidance using the Naval Postgraduate School ARIES AUV with the Blueview Blazed Array forward looking sonar. It includes a discussion on evaluating OA optimality, autopilot control design and sonar image processing. It concludes with a description of successful results from a recent demonstration

Use of artificial potential fields for UAV guidance and optimization of WLAN communications

Wireless local area networks (WLAN) are quickly becoming an important part of regional military operations. The use of standardized Internet protocols enables a wide variety of vehicles, sensors and personnel to interoperate more effectively. For autonomous underwater vehicles (AUV), they permit a potentially great improvement to distribute outputs from data intensive sensors like sonar and video to observers. For a fleet of AUVs tasked with area underwater search and survey, WLANs can facilitate situational awareness, re-tasking and expedience.

Control-Oriented Planar Motion Modeling of Unmanned Surface Vehicles

This paper describes a comparison of experimentally identified dynamic models for the planar motion of an unmanned surface vehicle (USV). The objective is to determine a model which is rich enough to enable effective motion planning and control, simple enough to allow straight forward parameter identification, and general enough to describe a variety of hullforms and actuator configurations. Starting from a three degree-of-freedom nonlinear model obtained from physical principles, we consider four simplified variants: (1) a linear model obtained by linearizing about straight, constant-speed motion, (2) a first order steering model (for turn rate) coupled with a first order speed model, (3) a second order steering model (for turn rate and sideslip angle), coupled with a first order speed model, and (4) a nonlinear model for low speed operation. The paper provides analysis of system identification data collected from field trials of three USV platforms in Summer 2010. The platforms represent three distinct control system implementations: a servo-actuated outboard engine, a servo-actuated jet-drive thruster, and differential thrusters.

Collaborative Unmanned Systems for Maritime and Port Security Operations

Abstract : This paper deals with some recent work ongoing at NPS, which attempts to show the utility of networked distributed vehicles for Maritime Interdiction, Riverine Operations, and related missions. We believe that these systems will be essential for dealing with the challenges in confronting these important National future needs.

AUV rendezvous trajectories generation for underwater recovery

For many years, autonomous underwater vehicles (AUVs) have been developed and employed for a myriad of tasks. Their ability to accurately collect and monitor oceanic conditions makes them a valuable asset for a variety of naval missions. Deploying and recovering AUVs, however, is currently largely limited to surface vessels or swimmers. The purpose of this paper is to demonstrate that by using a mathematical technique called a direct method of calculus of variations, it is possible for an AUV to autonomously compute and execute a trajectory that will allow for recovery by a submerged mobile recovery system (another AUV, submarine, etc.). The algorithm ensures that a smooth trajectory is produced that, while not traditionally optimal, is realistic and still close to the optimal solution. Also, using this technique allows the trajectory to be computed very rapidly allowing it to be recomputed every couple of seconds to accommodate sudden changes, possible adjustments and different disturbances, and therefore to be used in the real life.

Recent Developments for an Obstacle Avoidance System for a Small AUV

Abstract Improvements in high resolution small forward looking sonar (FLS) and computer processing have made it possible to develop an obstacle avoidance system (OAS) for small diameter Autonomous Underwater Vehicles (AUV). An AUV with such a system can maneuver around unanticipated obstacles that may be proud of the ocean floor. This ability can prevent serious damage to the vehicle or the environment. This paper discusses developments in control and computer vision techniques of an OAS designed to vertically avoid obstacles found on the ocean floor. Results are presented from recent in-water testing.

Wireless Communication Networks between Distributed Autonomous Systems Using Self-Tuning Extremum Control

This paper represents an effective optimization approach for building high bandwidth wireless communication networks between distributed autonomous systems using unmanned aerial vehicles as airborne relay nodes. A self-tuning extremum control technique is developed to find an optimal location of the aerial vehicles to provide maximum communication throughputs. The idea behind the self-tuning control is to use an on-line gradient estimator to identify the derivative of a cost function and to use this as an input to a gradient-based hill-climbing algorithm. The on-line estimation of the gradient of a performance function is achieved by utilizing a perturbation-based peek-seeking approach which provides a quantitative gradient value of the cost function in a numerical way. Flight experiments are conducted to evaluate the performance of the proposed airborne wireless sensor networking control algorithm.

Moving horizon estimation for undersea docking

The paper presents a new methodology for position estimation for terminal control of an AUV to an undersea docking station. It is designed to handle the sparse, noisy and intermittent measurements that can be common with Ultra Short Baseline (USBL) systems. The smoothing filter works over a fixed horizon of observations and is a modified approach to a Moving Horizon Estimation filter. The difference is in the optimization step. It utilizes a combination of piecewise polynomials known as episplines that are constrained by the vehicle dynamics and USBL observations to estimate the trajectory and output a predictive position estimate. This approach is compared with more common, non-linear, optimal filtering approaches to show the benefits under various simulated conditions. Filter performance is presented using in-sea docking station runs collected in Monterey Bay, CA.

Undersea acoustic communication maps for collaborative navigation

Communications play a key role in collaborative navigation algorithms. A better understanding of the ability to send and receive messages permits greater navigational flexibility and system robustness. This paper focuses on the building of an underwater acoustic communications map for collaborative navigation. The emphasis is in two areas - a local and global communications map. The local communications is defined with respect to a single destination reference point. Using a sample set of a priori signal to noise ratio acoustic modem data, Kriging techniques are used to create mean and variance map estimates. The global communications map is a compendium of local maps and is defined within a bounded survey space. Bayesian Inferencing is used for building the global map. It is based on REML parameter estimation of an anisotropic covariance function. The paper analyzes acoustic communication signal to noise datasets recently collected in Monterey Harbor, Monterey, CA and is used to demonstrate the above-described techniques.