RoboBoat: Development of an autonomous boat Anthony Redamonti ‘15 Nathan Corwin ‘15 Pratistha Shakya ‘15

Faculty Advisor: Professor John Mertens

This project endeavors to design and build an autonomous robot capable of competing in the Association for Unmanned Vehicle Systems International (AUVSI) foundation’s annual international 2015 RoboBoat competition. A team of Trinity class of 2014 engineering students started the RoboBoat project to build a boat following the guidelines for AUVSI foundation’s annual international RoboBoat competition. The robot was designed to accomplish tasks such as obstacle avoidance, speed testing and autonomous travel. However, by the end of the year, many of the team’s promised goals were unmet. This project endeavors to continue the previous work of students from the class of 2014 while also presenting new design challenges. New mechanical designs were implemented to increase the maneuverability of the boat, and highly intricate programming skills were necessary to develop the software architecture necessary for the boat to complete its tasks. Our primary objective is to make a robot capable of competing in the 2015 RoboBoat competition with additional objectives of redesigning and enhancing existing designs and adding the capability of completing bonus challenges in the competition.

Abstract

Problem Statement The goal of the RoboBoat project is to build a robotic boat capable of autonomous navigation that would be able to complete the obstacle avoidance challenge from the 2015 RoboBoat Competition. The boat should be able to navigate around obstacles towards a given destination.

2015 AUVSI RoboBoat Competition The Association for Unmanned Vehicle Systems International (AUVSI) Foundation hosts an annual competition in Virginia Beach, Virginia in conjunction with the Office of Naval Research (ONR) for autonomous watercrafts. The competition has different challenges including Automated Docking, Underwater Pinger Locating, UAV Interoperability, Navigation, and Obstacle Avoidance. The competition is designed to get college students interested in robotics and tackling the challenges of an aquatic environment.

Electrical Design

Obstacle Avoidance

Obstacle Avoidance Challenge

The Obstacle Avoidance challenge presents an obstacle field that the boat must navigate. As seen in in the diagram below, there are three entrances and exits to the obstacle field. The boat will be told beforehand which entrance and exit to use, and must navigate between these given gates hitting as few obstacles as possible. This challenge would require the boat to be able to identify and circumnavigate obstacles in its path while still maintaining a given course heading.

Rudder Placement and Design

Electronic Housing Box

Motor Controller The RioRand Dual Motor Controller was selected to control the amount of voltage supplied to both thrusters as it was the cheaper and more effective alternative to the Polulu Motor Controller. It is a more effective selection as only one controller is needed to control both thrusters, while two Polulu Motor Controllers would be needed to perform the same task.

Maximum turning force from a rudder is achieved when the majority of the surface area of each rudder is positioned directly behind each thruster. They were designed to be mounted to the back of the hull and hang below the mount in order to have most of their surface area directly behind the thrusters. The rudders were designed in SolidWorks and then 3D printed in ABS plastic. In order to test the rudders, the boat was timed turning 90° for a range of rudder angles measured from the neutral position. The results are graphed below. The dip in the graph indicates the angle for which the rudder provides the maximum turning torque.

Rudders mounted on boat

The electrical design features one 12V battery connected to a motor controller which powers the thrusters. The amount of voltage supplied to the thrusters depends on the pulse width modulation (PWM) signal output from an Arduino Uno to the motor controller. The motor controller also controls the direction of each thruster through the DIR pin set by the Arduino Uno. Both the motor controller and servos are powered by an external 6V battery supply, while the Arduino Uno and thrusters are powered by the 12V battery.

The electrical housing box contains all electrical components of the boat locked within a waterproof, clear acrylic case. On the top of the case cover are two electrical switches for the integrated 12V and 6 V power supplies.

Arduino Uno

RioRand Motor Controller

Sensors Two PING Ultrasonic Distance Sensors are placed on the front of the boat to detect obstacles in its path. PING Sensors are better than Sharp Infrared Sensors due to the fact that they have better range, a wider field of vision, and provide more consistent readings.

Illustration of PING sensor field of view

Compass and Navigation In order to navigate, the boat uses a magnetic compass to determine its current heading. The destination heading is determined by the given destination gate. The control system finds the difference between the given and current heading, and then uses this result to determine the appropriate angle for which to turn the rudders. The greater the difference between target and current heading, the more the rudders turn. The diagram for this proportional control system is displayed below. Additionally, obstacle avoidance is achieved by using the distance reading from the PING sensors to further adjust the rudder angle. The closer the obstacle, the more the boat turns to avoid it.

Navigation Control System Diagram

SolidWorks Model

PING Sensor

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ANGLE FROM NEUTRAL (DEGREE)

Max effective angle

Acknowledgements Professor Mertens, Professor Ahlgren, thank you for all of your help

and support. Thank you also to the 2014 Roboboat Team and the Ferris Athletic Center for the use of their equipment and facilities.

Rudders diagram neutral and turned

Waterproof Housing

HMC5883L Compass

Boat Design The boat features a Multi-Hull Design for stability in adverse conditions with two Seabotix BTD-150 thrusters positioned behind each pontoon for optimal thrust. Behind each thruster is a hanging semi-balanced rudder attached to a Traxxas 2056 high torque waterproof servo to achieve maximum turning force.

Complete Boat