James Mcmahon

• PhD Computer Science, MS Mechanical Engineering
• Researcher at United States Naval Research Laboratory

This paper presents an efficient approach for planning collision-free and dynamically feasible trajectories that enable a mobile robot to carry out tasks specified as regular languages over workspace regions. A sampling-based tree search is conducted over the feasible motions and over an abstraction obtained by combining the automaton representing...

This paper studies the problem of autonomous data collection where an underwater vehicle is required to reach several target regions within a specified time limit. The proposed approach takes into account the vehicle dynamics, the timevarying ocean currents, and the obstacles in the region in order to effectively plan a collision-free and dynamical...

This paper seeks to enhance the autonomy of underwater vehicles. The proposed approach takes as input a mission specified via a regular language and automatically plans a collision-free, dynamically feasible, and low-cost trajectory which enables the vehicle to accomplish the mission. Regular languages provide a convenient mathematical model that f...

We consider the coordinated escort problem, where a decentralised team of supporting robots implicitly assist the mission of higher-value principal robots. The defining challenge is how to evaluate the effect of supporting robots' actions on the principal robots' mission. To capture this effect, we define two novel auxiliary reward functions for su...

We provide theoretical bounds on the worst case performance of the greedy algorithm in seeking to maximize a normalized, monotone, but not necessarily submodular objective function under a simple partition matroid constraint. We also provide worst case bounds on the performance of the greedy algorithm in the case that limited information is availab...

We present the results of experiments performed using a small autonomous underwater vehicle to determine the location of an isobath within a bounded area. The primary contribution of this work is to implement and integrate several recent developments real-time planning for environmental mapping, and to demonstrate their utility in a challenging pra...

We consider an application where an unmanned underwater vehicle (UUV) equipped with an acoustic sensor seeks to estimate the location of surface ships using relative angle measurements to the ships. The estimation problem is challenging due to ships occasionally appearing and disappearing from the sensor's field of view. On occasion, poor geometry...

In marine robotics, data-collection operations often require an autonomous underwater vehicle (AUV) to collaborate with an unmanned surface vehicle (USV). The mission for the AUV is to reach many goal locations, avoid obstacles and unsafe areas, and maintain communication with the USV. The goals, however, are not known a priori, but are dynamically...

In this paper we propose an algorithm to actively track multiple moving targets using a bearing-only sensor in the presence of merged measurements. Merged measurements arise from sensor resolution constraints and therefore targets that are close in relative bearing to the sensor get reported as a single group measurement. We employ a merged measure...

This paper studies the problem of data collection where an autonomous underwater vehicle (AUV) is required to inspect several goals while staying within the communication range of an unmanned surface vehicle (USV) moving along a predefined path. A reward is associated with each inspected goal, and, so the overall objective is to increase the sum of...

The Orbiting Dubins Traveling Salesman Problem (ODTSP) is to plan a minimum-time tour for a Dubins vehicle model to inspect a set of targets in the plane by orbiting each target along a circular arc. This problem arises in underwater minehunting, where targets are mine-like objects on the sea bottom that are inspected by a sonar-equipped underwater...

This article describes the development and testing of a passive sonar, multitarget tracker, and adaptive behavior that enable an autonomous underwater vehicle (AUV) to detect and actively track nearby surface vessels. A planar hull-mounted hydrophone array, originally designed for active sonar, is repurposed for passive sonar use and provides acous...

We present an anytime Monte Carlo tree search (MCTS) algorithm to generate real-time, near-optimal search paths in large subsea environments. The MCTS planner continuously builds a tree of the search space until either the allowed time per move is reached or the budget constraint for the search mission is met. In order to improve the performance of...

In this paper, we describe an unmanned underwater vehicle (UUV) behavior designed to track nearby vessels using bearing-only measurements obtained from a rigidly mounted planar hydrophone array—one that was originally designed for active sonar use but is repurposed for passive sonar use. Upon detecting a target, a maneuver is executed to resolve th...

We address the challenge of computing search paths in real-time for subsea applications where the goal is to locate an unknown number of targets on the seafloor. Our approach maximizes a formal definition of search effectiveness given finite search effort. We account for false positive measurements and variation in the performance of the search sen...

Motivated by the predictions of a theoretical model developed to describe the acoustic flow force exerted on closely spaced nano-fibers in a viscous medium, we have demonstrated a novel concept for a particle velocity-based directional acoustic sensor. The central element of the concept exploits the acoustically induced normal displacement of a fin...

Mine Countermeasures (MCM) present a challenging motion-planning problem when taking into account ocean currents, complex bathymetry, and vehicle dynamics. In an effort to improve autonomous underwater vehicle (AUV) motion planning for MCM, this work presents a Physical Traveling Salesmen Problem (PTSP) approach as a way to quickly and robustly gen...

This paper presents an efficient approach for planning collision-free, dynamically-feasible, and low-cost motion trajectories that satisfy task specifications given as formulas in a temporal logic, namely Syntactically Co-Safe Linear Temporal Logic (LTL). The planner is geared toward high-dimensional mobile robots with nonlinear dynamics operating...

This paper seeks to enhance the mission and motion-planning capabilities of autonomous underwater vehicles (AUVs) operating in constrained environments in the littoral zone. The proposed approach automatically plans low-cost, collision-free, and dynamically-feasible motions that enable an AUV to carry out missions expressed as formulas in temporal...