Jacksonheaw
Posts: 4
Joined: Fri Jul 19, 2019 9:20 am

Autonomous Boat

Fri Jul 19, 2019 9:30 am

I'm currently working on this autonomous boat project using Raspberry Pi 3B+. The idea is to use the GPS and compass to implement the autonomous system. However, I am not sure which components (GPS & Compass) to use in the project.
Are there any recommendations on the GPS and Compass that are suitable for water-based autonomous system (for Raspberry Pi 3B+)? :)

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karrika
Posts: 1063
Joined: Mon Oct 19, 2015 6:21 am
Location: Finland

Re: Autonomous Boat

Fri Jul 19, 2019 7:19 pm

Jacksonheaw wrote:
Fri Jul 19, 2019 9:30 am
I'm currently working on this autonomous boat project using Raspberry Pi 3B+. The idea is to use the GPS and compass to implement the autonomous system. However, I am not sure which components (GPS & Compass) to use in the project.
Are there any recommendations on the GPS and Compass that are suitable for water-based autonomous system (for Raspberry Pi 3B+)? :)
The big picture of autonomous boats consists of two things:

1) Resilient PNT (Position Navigation Time)
You should not rely on a single source for the position of the boat, the direction and speed of the boat, the time.

2) Situations awareness
Is there something going on that you should take care of for safe sailing of the boat. This could be radars, cameras etc.

So one good idea would be to use some unit that use GPS, GLONASS and other GPS systems at the same time for a plausible position.

Jacksonheaw
Posts: 4
Joined: Fri Jul 19, 2019 9:20 am

Re: Autonomous Boat

Sun Jul 21, 2019 7:10 am

The big picture of autonomous boats consists of two things:

1) Resilient PNT (Position Navigation Time)
You should not rely on a single source for the position of the boat, the direction and speed of the boat, the time.

2) Situations awareness
Is there something going on that you should take care of for safe sailing of the boat. This could be radars, cameras etc.

So one good idea would be to use some unit that use GPS, GLONASS and other GPS systems at the same time for a plausible position.
My apologies. I forgot to mention that it is only a model boat, and obstacle detection and avoidance features might not be included here.
As for the tracking, are there any units that offer both GPS and GLONASS? Would it be sufficient for the autonomous guidance system? Meaning that compass can be excluded.

pfletch101
Posts: 503
Joined: Sat Feb 24, 2018 4:09 am
Location: Illinois, USA

Re: Autonomous Boat

Mon Jul 22, 2019 1:09 am

Jacksonheaw wrote:
Sun Jul 21, 2019 7:10 am
The big picture of autonomous boats consists of two things:

1) Resilient PNT (Position Navigation Time)
You should not rely on a single source for the position of the boat, the direction and speed of the boat, the time.

2) Situations awareness
Is there something going on that you should take care of for safe sailing of the boat. This could be radars, cameras etc.

So one good idea would be to use some unit that use GPS, GLONASS and other GPS systems at the same time for a plausible position.
My apologies. I forgot to mention that it is only a model boat, and obstacle detection and avoidance features might not be included here.
As for the tracking, are there any units that offer both GPS and GLONASS? Would it be sufficient for the autonomous guidance system? Meaning that compass can be excluded.
The problem with GPS/GLONASS for a model boat is that it is not very precise. A 3-4 meter potential error is unlikely to matter much for a full size boat on the ocean (unless you are docking, when someone will hopefully be looking at the dock!), but it will make life difficult for an autonomous model boat in more confined waters. You probably need to implement some inertial guidance system or set up your own beacons to allow better precision.

Jacksonheaw
Posts: 4
Joined: Fri Jul 19, 2019 9:20 am

Re: Autonomous Boat

Sun Jul 28, 2019 1:03 pm

The problem with GPS/GLONASS for a model boat is that it is not very precise. A 3-4 meter potential error is unlikely to matter much for a full size boat on the ocean (unless you are docking, when someone will hopefully be looking at the dock!), but it will make life difficult for an autonomous model boat in more confined waters. You probably need to implement some inertial guidance system or set up your own beacons to allow better precision.
So I happened to bump into this thing called Inertial Measurement Unit (IMU). Would it be helpful in this case for the model boat?
Is it true that the precision is in terms or cm? If that's the case it should probably work.

blimpyway
Posts: 151
Joined: Mon Mar 19, 2018 1:18 pm

Re: Autonomous Boat

Tue Jul 30, 2019 4:20 pm

No, affordable IMU modules will have too much drift to be any better than GPS.

Look into rtklib - it is an open source library which can be compiled in Pi/linux/windows

Here-s a explanation on how RTK works https://www.vboxautomotive.co.uk/index. ... t-work-rtk

Better google yourself for rtk and rtklib

blimpyway
Posts: 151
Joined: Mon Mar 19, 2018 1:18 pm

Re: Autonomous Boat

Wed Jul 31, 2019 9:00 pm

But I would also think if simple GPS is that bad. Most lakes or rivers I know worth having fun with a robot boat are big enough to keep the boat off shore with a 5-10m position precision.

Andyroo
Posts: 4231
Joined: Sat Jun 16, 2018 12:49 am
Location: Lincs U.K.

Re: Autonomous Boat

Wed Jul 31, 2019 10:00 pm

blimpyway wrote:
Wed Jul 31, 2019 9:00 pm
But I would also think if simple GPS is that bad. Most lakes or rivers I know worth having fun with a robot boat are big enough to keep the boat off shore with a 5-10m position precision.
Sandbanks?
Need Pi spray - these things are breeding in my house...

HoggsUK
Posts: 5
Joined: Thu Aug 08, 2019 12:16 pm

Re: Autonomous Boat

Thu Aug 08, 2019 12:23 pm

Jacksonheaw wrote:
Fri Jul 19, 2019 9:30 am
I'm currently working on this autonomous boat project using Raspberry Pi 3B+. The idea is to use the GPS and compass to implement the autonomous system. However, I am not sure which components (GPS & Compass) to use in the project.
Are there any recommendations on the GPS and Compass that are suitable for water-based autonomous system (for Raspberry Pi 3B+)? :)
I'm just starting out with the same project. I have a pi, and that's it hahahaha. I'd love to do the https://www.microtransat.org challenge but if I could get a boat to go round a lake, I'd take that!

Jacksonheaw
Posts: 4
Joined: Fri Jul 19, 2019 9:20 am

Re: Autonomous Boat

Thu Aug 08, 2019 5:20 pm

HoggsUK wrote:
Thu Aug 08, 2019 12:23 pm

I'm just starting out with the same project. I have a pi, and that's it hahahaha. I'd love to do the https://www.microtransat.org challenge but if I could get a boat to go round a lake, I'd take that!
Glad to hear that! :lol:
Hope to hear more from you, especially with any problems encountered just in case we have the same problem :?
Currently I'm still deciding which components to use, particularly this SIM7600E-H 4G HAT.
It can be used for cellular connection and location detection, but I'm wondering if it can detect the heading as well? Would be perfect if that's the case.

HoggsUK
Posts: 5
Joined: Thu Aug 08, 2019 12:16 pm

Re: Autonomous Boat

Thu Aug 08, 2019 9:40 pm

You're already way ahead of me! I've only just completed a magic mirror to get the basics of understanding how it works.

Over the summer I'm going to be looking the auto-boat. Definitely happy to keep in the loop & will be posting on here.

In theory, I want to set way points and I want the boat to head to these markers. However, I'd like it to assess as it goes and if it's heading of course, I want it to take action...whether by rudder or prop thrust etc.

HoggsUK
Posts: 5
Joined: Thu Aug 08, 2019 12:16 pm

Re: Autonomous Boat

Fri Aug 09, 2019 12:15 pm

Jacksonheaw wrote:
Thu Aug 08, 2019 5:20 pm

Glad to hear that! :lol:
Hope to hear more from you, especially with any problems encountered just in case we have the same problem :?
Currently I'm still deciding which components to use, particularly this SIM7600E-H 4G HAT.
It can be used for cellular connection and location detection, but I'm wondering if it can detect the heading as well? Would be perfect if that's the case.
It looks a neat piece of affordable kit.

I've been looking at these ones for inspiration. This guy used a separate system
https://www.instructables.com/id/Making ... rry-Pi-a-/

https://blog.sotonsailrobot.org/

I am wanting to use GSM as I would be sticking to lakes or near coastal shores as the signal will reach. I'm trying to stick to a small budget rather than sat phones and data plan start to rack up £'s.

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karrika
Posts: 1063
Joined: Mon Oct 19, 2015 6:21 am
Location: Finland

Re: Autonomous Boat

Fri Aug 09, 2019 5:00 pm

Hi guys,

If you cannot afford expensive gyros then there is one very nice way of combining the sensors found on a mobile phone or some HAT board.

See the clip at http://x-io.co.uk/open-source-imu-and-ahrs-algorithms/ and the initial paper published by Madgwick. At the end of the paper there is a very small C-code program that implements a MARG (Magnetic Angular Rate and Gravitational sensor) Fusion Filter. Luckily the modern chips found on a HAT will provide all the required sensor values for MARG.

There is also some scientific papers with simple source codes in C of how to make a reliable position and direction out of the sensors.

The problematic part in a gyro is the drift. When you accelerate or turn you may actually get the direction to drift. Once the vessel is steady you can check the magnetic direction. If it is consistent with the gyro calculation you are happy. Otherwise you may adjust it.

Acceleration has a little similar dilemma. Once you are turning and changing speed you really don't know your exact orientation. But once you run steady then the earths gravity pulls you down.

These automatic adjustments are part of the Fusion Filter algorithm presented here.

So by taking many sensors like magnetic north and earth gravity in the algorithm you can create a cheap, accurate system that is better than the sensors alone.

At the same time you have a wonderful chance to get introduced to quaternion math that is used all over the place from computer games to drones today.

The math and the code is not so cryptic. By reading through the research papers you get a very nice understanding of components required by resilient PNT navigation for autonomous vessels. (Both real ones and small model boats.)

Perhaps you could even expand the fusion filter by finding out what the time is and where the sun is. Or some image recognition algorithms that could see if the lighthouses are where they are supposed to be? Then the algorithm would also care for terrestrial navigation and not just use satellites.

HoggsUK
Posts: 5
Joined: Thu Aug 08, 2019 12:16 pm

Re: Autonomous Boat

Fri Aug 09, 2019 5:55 pm

HI @karrika,
I've also been looking at this component https://www.rooco.eu/products/moitessie ... -receiver/ and wonder if this would be the golden ticket?
  • High-sensitivity (better than -112 dBm) dual channel AIS receiver with SMA antenna connector.
    High-performance GNSS receiver with integrated patch antenna and external antenna support via BNC connector.
    Compass, heel and trim from gyroscope, accelerometer and magnetometer sensors (IMU).
    Barometric pressure.
    Standalone usage or in combination with Raspberry Pi (). Sensors are directly accessible via Raspberry Pi. Standalone usage requires 3.3V power supply and sensors are controlled by the HAT’s microcontroller.
    Fully compatible with Raspberry Pi models supporting 40-pin IO header.
    Data communication via SPI (AIS, GNSS and meta data) and via I2C (sensor data).Data accessible via device driver and device file.
    Supports ID EEPROM and automatic device tree loading.
    3 status LEDs (AIS status, GNSS status, error).
    Full OpenPlotter compatible. Plug and play.

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karrika
Posts: 1063
Joined: Mon Oct 19, 2015 6:21 am
Location: Finland

Re: Autonomous Boat

Tue Aug 13, 2019 1:24 am

Sounds like a perfect find. You have all the sensors required for sailing. It does provide the raw sensors. Perhaps the navigation software could offer some Fusion Filter module to make the reliability good enough for real sailing. As this has GNSS you can get pretty accurate feedback to your compass calculation over time. The navigation software is also open source so it would be a good idea to create some fusion filter or kalman filter for increased reliability in case it does not yet have it.

HoggsUK
Posts: 5
Joined: Thu Aug 08, 2019 12:16 pm

Re: Autonomous Boat

Mon Aug 19, 2019 7:43 pm

karrika wrote:
Tue Aug 13, 2019 1:24 am
Sounds like a perfect find. You have all the sensors required for sailing. It does provide the raw sensors. Perhaps the navigation software could offer some Fusion Filter module to make the reliability good enough for real sailing. As this has GNSS you can get pretty accurate feedback to your compass calculation over time. The navigation software is also open source so it would be a good idea to create some fusion filter or kalman filter for increased reliability in case it does not yet have it.
Superb. I was away on hols so apologies on delayed reply.

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