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OpenTransat

Building an Autonomous Sailboat That Pursues to Cross the Atlantic Ocean

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The goal is to build a fully autonomous sailboat that will cross the Atlantic Ocean while following strict rules of the Microtransat Challenge – a transatlantic race for autonomous boats. According to the rules, the maximum length of the boat is limited to 2.4 metres and the target point across the ocean must be reached within 25 km radius. It's quite a challenge, isn't it?

Our first transatlantic attempt commenced on September 12, 2016. The boat was launched from Newfoundland and was expected to reach its final destination in Ireland.

The boat went through a series of troubles and automatic recoveries, so it was really exciting to watch the progress.

The name OpenTransat suggests that all the details including the code, schematics and actual build process will be revealed. Going open-source will definitely speed up the development of autonomous sailboats and help others build upon a proven concept. We are just at the beginning of a long, thrilling journey!

Track the Boat

There are three trackers which are located on the boat. One Iridium tracker (RockBlock module) which is represented by the green color, and two Globalstar trackers (SPOT Trace) which are identified by the red and yellow colors.

On the tracking map, you can also read comments with explanations and assumptions, outlining what could possibly create challenges. Is the boat mechanically damaged by a wild storm? Was it hit by a floating object? Hopefully, we will find the definite answers after the boat recovery and a thorough examination.

Track the boat here:

http://www.opentransat.com

Launched from Newfoundland

The boat was shipped to Newfoundland in several packages and launched from a fishing boat about 5.5 km (3.4 miles) from the harbour. The route from Newfoundland to Ireland has been chosen as the shortest path across the Atlantic, and it's also in the direction of prevailing winds.

How It Works

The main framework is built from aluminum profiles on top of a surfboard, so the boat will never sink. The boat is balanced by a heavy keel that would flip the boat back over in case it flips. This concept has been chosen for its fast assembly and also because of the ability to make easy modifications. It's more like a proof of concept, with the purpose to test different hardware modules and navigation software before proceeding to a more streamlined design.

The sail is designed to resist high ocean winds. It is made from ripstop nylon that is reinforced by nylon webbing and thick carbon fiber tubes.

The electronics is securely sealed in a Pelican case and two polycarbonate cases. The Pelican case contains four LiFePo4 batteries, solar charge controller and an Arduino-based controller for navigation.

Satellite Communication

The Iridium satellite module, as well as GPS, is in a separate polycarbonate case for better signal reception. Another polycarbonate case contains a SPOT tracker and a GPS logger too.

You can find more about hacking SPOT Trace in the project log.

Rudder

The video below demonstrates the rudder being turned by a servo when the compass is off-course.

The servo alone is said to be IP67 waterproof, but what if the boat encounters 5-meter waves? A few layers of latex gloves filled with a silicone grease were added for extra protection.

Camera

A Git2 action camera is recording a 15-second video every 30 minutes. The camera has been hacked to be powered by the primary battery source and controlled by Arduino.

The video is stored on a 128 GB SD card, and it can be accessed only when the boat is recovered because it is unrealistic to transmit any part of the video over a satellite network. Sending a single high-resolution image would cost hundreds of dollars, not to mention that the speed is significantly lower than dial-up.

What's next?

What comes after failure, is another trial. A new boat built from super-strong materials with radically improved hardware and software will be definitely more capable to cross the ocean. Stay tuned for the next transatlantic attempt in 2017!

  • Boat Controller

    Andy Osusky06/07/2017 at 13:37 0 comments

    The new boat controller consists of two PCBs – the Navigator mounted on top of the Expansion Board.

    The Navigator will be responsible for the most important tasks like navigation, collision avoidance and sending messages. The Expansion Board that will provide additional functions more specific to the boat. This modular design allows to make quick modifications on the Expansion Board while keeping the more complex Navigation Board unchanged.


    Here are all features of the boat controller:

    • The microcontroller is Atmega2560 running at 16 MHz. It has been chosen because it's widely used in development boards like Arduino Mega and there's a vast amount of available libraries for various sensors.
    • It can be programmed over Wifi. This will make life easier as there is no need to open the hatch and connect the cable for programming. The boat can be tested in the ocean while staying connected to a laptop located on the shore or motorboat. With a long range Wifi antenna, the program can be uploaded even hundreds of meters over the air.
    • Tilt compensated compass. There will be also an auxiliary compass that will be mounted far enough from magnetic noise.
    • Accelerometer & gyro. The motion sensor will give us a better idea about what the boat is actually doing, especially during storms and high winds. It will report pitch & roll, average wave height, etc.
    • Battery power sensor.
    • 2 MB flash memory for data logging.
    • Experimental 256 KB FRAM memory which is faster than flash.
    • Temperature, pressure and humidity sensor. It may discover potential problems inside the waterproof housing such as leaking, overheating or need for pressure compensation.
    • Watchdog timer based on a low-power microcontroller that monitors the “heartbeat” of the main CPU. If the Navigator doesn't respond for a minute or it reports any kind of failure, the watchdog will cut power for a few seconds. This is how we usually fix problems. :)
    • A couple of MOSFET switches to turn on particular hardware only when needed: Linux computer with a camera, satellite modem, AIS receiver (for collision avoidance), RC receiver and water pumps. Wondering what the water pumps are for? They will pump water out of the boat if flood sensors detect big trouble...

    Power Sensor

    There will be one additional board that will measure voltage and current of each solar panel separately. It will be interesting to see which panel is shaded by the sail at any particular time.

    Complete hardware scheme:

    The source is published on GitHub:

    http://github.com/opentransat

  • New Design

    Andy Osusky11/22/2016 at 10:05 0 comments

    Below is the design of the new autonomous boat that will attempt to cross the Atlantic. It will be built from carbon fiber, fiberglass and Kevlar. The total length will be 2.2 metres (7.2 feet). The long and narrow hull is optimized for speed. Instead of a typical sail, there is a rigid wingsail as seen on modern yachts.

    First, I am going to build a miniaturized version to test the hardware and software. I will keep you updated on the progress!

  • Additional Trackers and Hacking SPOT Trace

    Andy Osusky11/03/2016 at 10:01 0 comments

    As explained in the project details, there are three trackers on the boat. The RockBlock module which is connected to the Arduino-based controller is transmitting interesting data via the Iridium Short Burst Data service; such as the GPS position, the battery voltage, power consumption, temperature, wind speed, etc.

    In case the main hardware fails, there is another tracker called SPOT Trace that is transmitting only the current position via the Globalstar satellite network. It has an independent power source made of four NiMH AA batteries being recharged by two 6V / 50mA solar panels.

    Because SPOT Trace may permanently turn off in case it loses power (for example, when the batteries completely discharge or when the connection breaks for a moment in rough ocean conditions), a timer 555 periodically sends short pulses to the SPOT Trace switch.

    You need pretty good soldering skills to connect the wires to the switch. All soldered connections that may break off were potted with epoxy. Another great hack was to solder wires for an external battery source for two reasons – a larger battery capacity would provide enough power during a series of rainy days. Secondly, I wouldn't trust the micro USB connection.

    For testing purposes, a vibration motor from a mobile phone was glued to the vibration sensor to ensure that SPOT Trace continuously reports position, even when it is not moving. It is not necessary for the ocean as the ocean waves are continuous and never stop. :)

    The day before launch, I added a third tracker which is another SPOT Trace. However, it's powered only by non-rechargeable batteries. Based on the tracker power consumption when reporting position every hour, eight D cell alkaline batteries should last about two years.

  • Navigation Software from Scratch

    Andy Osusky10/31/2016 at 12:45 0 comments

    Existing open-source solutions for drones were not suitable for this project. Below are the most important points where the boat differs from typical applications:

    1) Tilt-Compensated Compass

    A small boat is constantly bouncing up and down while riding high waves. Therefore a tilt-compensated compass LSM303D was used to find the correct heading. The compass combines a 3-axis accelerometer and 3-axis magnetometer.

    2) Spherical Coordinates

    If you fly a drone, you probably don't send it over vast distances across an entire continent. Some flight controllers do calculations by using the Pythagoras theorem, which is valid only on a flat surface. For a greater precision, we need to count in the Earth curvature which is significant for the path across the Atlantic.

    3) More Sophisticated Error Correction

    If you try to drive a small powerboat in wild ocean conditions, you will find out quite quickly that it's not as easy as driving a car. As the boat is often turned by the waves from side to side, it has to take action by adjusting the rudder, but not too often as the servo would quickly wear out. The servo has to be operational for months! A PID controller has to be implemented to keep the boat in one direction while being friendly to the servo at the same time.

    4) Magnetic Declination

    Magnetic declination, i.e. the angle between magnetic north and true north, can make a difference by as much as 20 degrees. While it is not absolutely critical for a successful mission, it's worth implementing the World Magnetic Model into the navigation software to measure the heading more precisely. The actual model is a very complex formula with plenty of experimental constants that can change over time. So, I calculated the values of declination on a sphere mesh and stored them in the Arduino flash memory.

  • Electronics and Sensors

    Andy Osusky10/28/2016 at 10:03 0 comments

    The main electronic components are contained in a Pelican iM2100 case. They are fully protected by steel boxes in order to resist heavy impacts which can be caused by the ocean waves and delivery guys.

    I have read too many horror stories about a leaking Pelican case, so to be extra sure this wouldn't cause me the same problems as others have encountered, I sealed it with silicone prior to the real mission.

    The main components are:

    • Four 3.2V 36Ah LiFePo4 cells that are being charged by a 100W solar panel. There is also a balance charging PCB connected to the batteries.
    • A solar charge controller for charging the batteries. It also protects the batteries from being overcharged or over-discharged.
    • A navigation controller made from common hardware: Arduino Mega where the navigation program is loaded. A temperature and humidity sensor, a voltage/current sensor, FRAM memory for data logging, and a watchdog timer (we'll talk about it soon!)

    Data Logging

    Firstly, the board was designed to record data on a uSD card. However, it has two drawbacks that can be avoided by using a FRAM memory instead:

    1. SD consumes more power than FRAM.
    2. If a file gets corrupted, the current SD library holds the program for a few seconds every time it tries to write to the card. File corruption can accidentally happen during low voltage periods or unexpected shutdown during writing. It's not likely, but the risk is not acceptable.

    The final decision was adding a FRAM memory chip. The read/write operations are much easier to handle.

    Hardware Watchdog Timer

    How do you fix a Wi-Fi router or a phone so that it works 99% of the time?

    You simply turn it off, and back on. Aside from a typical watchdog timer, the hardware watchdog timer resets the boat every 8 hours. It also listens to the main CPU “heartbeat”, and it resets the boat if the program is not working correctly. Or, if the CPU is idle for 3 minutes. Resetting the boat means that every single component, including the GPS and compass, is being disconnected from the power source for 5 seconds. Arduino Micro is overkill for this purpose. However, it has been chosen as a quick and easy solution. In the next design, I will use an MSP430 or a similar ultra-low-power microcontroller.

    As well as sensors being useful for navigation, there are also additional sensors for measuring environmental data:

    • Humidity inside the waterproof housing. Even if a small drop of water gets inside the waterproof housing, the humidity will sharply increase.
    • The temperature inside the waterproof housing. The batteries, solar charge controller, voltage regulators and the CPU generate heat. So, we need to be careful when the electronics are sealed in a plastic case. Experience has confirmed that overheating is not an issue in the cold waters of the Atlantic Ocean. Even if the case has no heat sink, the inside temperature is only about 4-7 °C (40-45 °F) greater than the outside temperature.
    • Water temperature and air temperature. In case the boat flips over, the air temperature and water temperature will replace each other. If someone pulls the boat out of the water, the water temperature sensor will measure the air temperature. If the boat hits a big iceberg, the water temperature will reach a value close to 0 °C (32 °F).

    Having all of these fancy sensors on board is not only more fun, but the sensors also tell us a lot of useful information about the boat condition.

    The RockBlock and GPS modules are in a separate polycarbonate case for a better signal reception. The compass is also located far enough from the solar panel and anything ferromagnetic.

  • Boat Transportation and Launch

    Andy Osusky10/27/2016 at 09:16 0 comments

    One of the challenges was the logistics of transporting the boat to Newfoundland and launching it far enough from a rocky shore. With this in mind, it has been designed to be easily disassembled and packed into several small packages. The packages were shipped using different courier services to optimize the cost. The boat was assembled in a rented storage space and moved to the harbour in a van.

    To get help with the launch, I was talking to random people along the harbour in a small fishing village. It didn't take long until I found a family house with helpful fishermen who had an awesome boat!

    During a perfect weather window, we threw the boat overboard about 5.5 km (3.4 miles) from the harbour, leaving it at the mercy of the harsh Atlantic Ocean.

View all 6 project logs

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