Electrical Team Progress Update – May 2014

by Ellinor Crux, Electrical Team Lead

For the UBC Sailbot’s transatlantic vessel to be successful in crossing the Atlantic Ocean, an electrical system is needed to bridge the gap of the software systems discussed in previous posts to the new boat hull. Over the past 8 months, the electrical team has been researching and testing electrical components that will potentially be used on the final transatlantic boat. Through this blog post, each component will be explored in detail.

Sensors

The sensors are the figurative eyes and ears for the boat. They will provide all the information the boat will need to navigate safely to it’s destination. Below are some of the sensors we have been working with.

Wind Sensor

The basics of sailing require that you know which way the wind is heading! The wind sensor measures the speed and direction of the wind. This allows the boat to determine the best way to align it’s sails to travel in a desired direction. The wind sensor we will be using is a model CV7 from LCJ Capteurs. This wind sensor is ultrasonic, meaning it measures the velocity of the wind by sensing the speed of ultrasonic sound waves it emits as they travel between transducers. The ultrasonic operation eliminates the need for moving parts, which enhances reliability of the sensor in marine environments over the traditional cup-and-vane wind sensors.

GPS

Knowing where you are is crucial if you want to know where to go. The GPS module will provide location data for the boat, allowing us to track its movements, and estimate its speed and trajectory.The GPS module and antenna we are using are the Flexpak-G2 Novatel OEMStar GPS. We would like to thank Novatel for donating the GPS module and antenna.

Compass and Accelerometer

The compass and accelerometer allow the boat to determine its heading and orientation in space.The accelerometer also can sense the movement up and down waves, which will be important as a safety check, should the boat suddenly accelerate due to a storm or a large wave.

Communication

Satellite

Once we let the boat go, it would be reassuring if we know where it went! That’s where the communications systems come in. The satellite will report the boat’s location and supply the boat with weather data. The weather data will be used as part of the boat’s path-finding algorithm. The location of the boat has to be reported every day, but we want to keep an eye on the fruit of our labours, so we’ll make sure it calls home more often. We are using a Rockblock satellite modem from “Rock Seven”. Currently, we are working on completing a software library for use with the modem.

We would like to thank Rock Seven for supplying us with credits for use on their satellite service.

Automatic Identification System (AIS)

Our boat is not going to be alone out there. We have to make sure it doesn’t run into any other boats! The Automatic Identification System is a module which allows vessel to vessel communication of heading, location, and planned route. This functionality is important for our boat in navigating around other vessels. We are also exploring ways of detecting vessels or obstacles without AIS technology onboard.

Power

The journey across the Atlantic ocean wouldn’t be possible if the electronics stopped running. Being on the water for at least 2 weeks is bound to use up a lot of power! The main task of the Power Systems subteam is to design the voltage supply and its charging circuit in order to power the electrical components on the boat.

Batteries

The batteries will consist of 4 sets 3 battery cells at 3.7 volts, giving us a supply voltage 11.1 V. A DC/DC converter will be used to step down the higher supply voltage to one which can be used by the digital components. The DC/DC converter we will be using is a Texas Instruments 6A 12V SWIFT DC/DC.

Solar Panels

Sooner or later, the batteries will run out of power. We have decided to harness solar energy due the robustness and reliability of the currently available technology. We have decided to use Solbian brand flexible solar panels of the SP series. Not only are Solbian panels manufactured for marine applications, their light and flexible nature give us options for mounting. Currently we are trying to determine the exact size and location of the solar panels so that we can move on to ordering them. Any input from people experienced with the use of solar panels in marine environments would be welcome!

Motors

The motors are the muscles of the boat. There are two motors on the vessel, one servo motor to control the rudder; and a winch to control the sail.

Servo Motor

The rudder motor is a Torxis i00600 servo motor. This motor was chosen for its high torque output which will be necessary to hold the boat on course as winds pick up and the sea gets rough. The motor was also chosen for its compatibility with the power systems design and three position feedback. The three position feedback feature polls the motor constantly checks it position against the last logged position command, adjusting it accordingly if it has been forcibly moved.

Sail Winch

For the sail winch motor we are currently discussing with our industry mentor and the manufacturer over the final designs. Fabrication on our custom winch motor will begin soon.

Redundancy

We can never be sure everything will go exactly as planned; that’s why we have fail-safes! The current design of the electrical system has several redundancies and fail-safes.The overall design can be viewed in the diagram below. Notice that most components are duplicated and segregated into separate boxes. The segregation of components minimizes collateral damage should there be a leak or damage to the vessel which causes some of the electrical systems to fail.

Sailbot layout

Click on image to see full resolution version.

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