1,327 research outputs found
Model Checking for Decision Making System of Long Endurance Unmanned Surface Vehicle
This work aims to develop a model checking method to verify the decision
making system of Unmanned Surface Vehicle (USV) in a long range surveillance
mission. The scenario in this work was captured from a long endurance USV
surveillance mission using C-Enduro, an USV manufactured by ASV Ltd. The
C-Enduro USV may encounter multiple non-deterministic and concurrent problems
including lost communication signals, collision risk and malfunction. The
vehicle is designed to utilise multiple energy sources from solar panel, wind
turbine and diesel generator. The energy state can be affected by the solar
irradiance condition, wind condition, states of the diesel generator, sea
current condition and states of the USV. In this research, the states and the
interactive relations between environmental uncertainties, sensors, USV energy
system, USV and Ground Control Station (GCS) decision making systems are
abstracted and modelled successfully using Kripke models. The desirable
properties to be verified are expressed using temporal logic statement and
finally the safety properties and the long endurance properties are verified
using the model checker MCMAS, a model checker for multi-agent systems. The
verification results are analyzed and show the feasibility of applying model
checking method to retrospect the desirable property of the USV decision making
system. This method could assist researcher to identify potential design error
of decision making system in advance
Software Considerations for Subscale Flight Testing of Experimental Control Laws
The NASA AirSTAR system has been designed to address the challenges associated with safe and efficient subscale flight testing of research control laws in adverse flight conditions. In this paper, software elements of this system are described, with an emphasis on components which allow for rapid prototyping and deployment of aircraft control laws. Through model-based design and automatic coding a common code-base is used for desktop analysis, piloted simulation and real-time flight control. The flight control system provides the ability to rapidly integrate and test multiple research control laws and to emulate component or sensor failures. Integrated integrity monitoring systems provide aircraft structural load protection, isolate the system from control algorithm failures, and monitor the health of telemetry streams. Finally, issues associated with software configuration management and code modularity are briefly discussed
An Appearance-Based Tracking Algorithm for Aerial Search and Rescue Purposes
The automation of the Wilderness Search and Rescue (WiSAR) task aims for high levels of understanding of various scenery. In addition, working in unfriendly and complex environments may cause a time delay in the operation and consequently put human lives at stake. In order to
address this problem, Unmanned Aerial Vehicles (UAVs), which provide potential support to the
conventional methods, are used. These vehicles are provided with reliable human detection and
tracking algorithms; in order to be able to find and track the bodies of the victims in complex
environments, and a robust control system to maintain safe distances from the detected bodies.
In this paper, a human detection based on the color and depth data captured from onboard sensors
is proposed. Moreover, the proposal of computing data association from the skeleton pose and a
visual appearance measurement allows the tracking of multiple people with invariance to the scale,
translation and rotation of the point of view with respect to the target objects. The system has been
validated with real and simulation experiments, and the obtained results show the ability to track
multiple individuals even after long-term disappearances. Furthermore, the simulations present the
robustness of the implemented reactive control system as a promising tool for assisting the pilot to
perform approaching maneuvers in a safe and smooth manner.This research is supported by Madrid Community project SEGVAUTO 4.0 P2018/EMT-4362)
and by the Spanish Government CICYT projects (TRA2015-63708-R and TRA2016-78886-C3-1-R), and Ministerio
de Educación, Cultura y Deporte para la Formación de Profesorado Universitario (FPU14/02143). Also,
we gratefully acknowledge the support of the NVIDIA Corporation with the donation of the GPUs used for
this research
A COLLISION AVOIDANCE SYSTEM FOR AUTONOMOUS UNDERWATER VEHICLES
The work in this thesis is concerned with the development of a novel and practical collision
avoidance system for autonomous underwater vehicles (AUVs). Synergistically,
advanced stochastic motion planning methods, dynamics quantisation approaches,
multivariable tracking controller designs, sonar data processing and workspace representation,
are combined to enhance significantly the survivability of modern AUVs.
The recent proliferation of autonomous AUV deployments for various missions such
as seafloor surveying, scientific data gathering and mine hunting has demanded a substantial
increase in vehicle autonomy. One matching requirement of such missions is
to allow all the AUV to navigate safely in a dynamic and unstructured environment.
Therefore, it is vital that a robust and effective collision avoidance system should be
forthcoming in order to preserve the structural integrity of the vehicle whilst simultaneously
increasing its autonomy.
This thesis not only provides a holistic framework but also an arsenal of computational
techniques in the design of a collision avoidance system for AUVs. The
design of an obstacle avoidance system is first addressed. The core paradigm is the
application of the Rapidly-exploring Random Tree (RRT) algorithm and the newly
developed version for use as a motion planning tool. Later, this technique is merged
with the Manoeuvre Automaton (MA) representation to address the inherent disadvantages
of the RRT. A novel multi-node version which can also address time varying
final state is suggested. Clearly, the reference trajectory generated by the aforementioned
embedded planner must be tracked. Hence, the feasibility of employing the
linear quadratic regulator (LQG) and the nonlinear kinematic based state-dependent
Ricatti equation (SDRE) controller as trajectory trackers are explored.
The obstacle detection module, which comprises of sonar processing and workspace
representation submodules, is developed and tested on actual sonar data acquired
in a sea-trial via a prototype forward looking sonar (AT500). The sonar processing
techniques applied are fundamentally derived from the image processing perspective.
Likewise, a novel occupancy grid using nonlinear function is proposed for the
workspace representation of the AUV. Results are presented that demonstrate the
ability of an AUV to navigate a complex environment.
To the author's knowledge, it is the first time the above newly developed methodologies
have been applied to an A UV collision avoidance system, and, therefore, it is
considered that the work constitutes a contribution of knowledge in this area of work.J&S MARINE LT
Distributed Control Architecture
This document describes the development and testing of a novel Distributed Control Architecture (DCA). The DCA developed during the study is an attempt to turn the components used to construct unmanned vehicles into a network of intelligent devices, connected using standard networking protocols. The architecture exists at both a hardware and software level and provides a communication channel between control modules, actuators and sensors.
A single unified mechanism for connecting sensors and actuators to the control software will reduce the technical knowledge required by platform integrators and allow control systems to be rapidly constructed in a Plug and Play manner. DCA uses standard networking hardware to connect components, removing the need for custom communication channels between individual sensors and actuators.
The use of a common architecture for the communication between components should make it easier for software to dynamically determine the vehicle s current capabilities and increase the range of processing platforms that can be utilised. Implementations of the architecture currently exist for Microsoft Windows, Windows Mobile 5, Linux and Microchip dsPIC30 microcontrollers.
Conceptually, DCA exposes the functionality of each networked device as objects with interfaces and associated methods. Allowing each object to expose multiple interfaces allows for future upgrades without breaking existing code. In addition, the use of common interfaces should help facilitate component reuse, unit testing and make it easier to write generic reusable software
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