A lot of people have contacted me for more pics, so I thought I would throw up some more. I will give some minimal content with them. If you have any questions, fire away and I will answer in the comments.

The first iteration of controller and Pixhawk. At the time I thought The Pi would be too big and draw too much power. Power was ok, but definitely too big.

When I got the hull from Radtek, I originally planned to use three 50 watt solar panels since I could not find a 150 watt panel that was narrow enough to fit on top. The width of the hull is 21". The length is 92"

I also planned to use the push pull system for the rudder. I quickly found out that even a heavy duty servo could not tolerate a week pushing water back and forth in my torture test bucket.

This caused me to rethink and redesign the rudder system. I eventually went with a thru-hull rudder system. This is a typical powerboat brass rudder port mounted on top of a 1/4" carbon fiber plate. On the bottom of the hull is a 1/4" ABS plastic plate. With weight ever increasing, I went with a kayak rudder and an 1" diameter aluminum rudder shaft.

After weeks breadboarding everything and testing, the final control system looked something like this. As you can see from the picture I moved from the servo rudder control to a linear servo. This one has 135 lbs of thrust and handled the bucket challenge with no problems.


The servo installed in the hull. I was very fortunate that the servo lined up almost perfectly with the rudder aperture. This is the only pic I could find of the servo so the candy obscures part of it.

Once all the systems were figured out, the challenge became how to fit them into a small enough water tight container. This caused a lot of grief.  This is a first attempt.

Finally I found the perfect waterproof container for the electronics

At the back are the waterproof ports for most of the electronics. The exposed sma connector attaches to the Satellite antenna. In all I drilled about 15 holes in the case for cabling.


Expecting that the ocean will batter the crap out of this, I mounted a carbon fiber plate to the the hull and bolted the electronics to the hull via vibration mounts. These mounts will keep the electronics about an inch off the hull. Hopefully the vibration will be significantly reduced.

Juggling family and a full time job meant that everything was done from 8pm till the wee hours of the morning, hence this taking a year (and counting). Soldering success at 3am. I had blown through 4 boards before this one by letting the solder touch and failing to clear it properly before plugging the controller board into a power source. 

I went with a 100AH battery after figuring in the power requirements. Just running the electronics 24/7 added up quickly not to mention powering the motor and the rudder. Since this platform is designed to drift with the current and monitor the ocean/air once it reaches a certain point, there will not be a constant high load demand on the battery. Getting to its destination is another power story entirely. lol...

I wanted to be able to stay on-station for many days even in the event of a lack of sunshine. A 100ah LIFePO4 battery weighs about 26lbs. You can see the battery installed in the hull in my previous post.

Once the battery was in, I then had to wire up to the charge controller and also wire up a secondary chrage port so the battery could stay charged while inside. At one point I had wires coming out of all parts of the boat. The usb ports for talking to the pixhawk and other devices are in the shot as well

That's all for now. If you have any questions, let me know.

I should have some more photos up at 

http://twitter.com/pacificbots

Views: 2024


Moderator
Comment by Gary Mortimer on January 5, 2015 at 12:58pm

Total admiration, love it!

Comment by David Boulanger on January 5, 2015 at 1:18pm

Great job but I think your hull is too narrow.  Just my opinion.

Regards

David R. Boulanger

Comment by PacificBots on January 5, 2015 at 1:20pm

In the top pic i described the autopilot as a pixhawk, when it is an apm 2.6.


Admin
Comment by Thomas J Coyle III on January 5, 2015 at 1:25pm

@PB,

Why an aluminum rudder shaft? It will quickly start to corrode in salt water.

Maybe brass or stainless steel?

Regards,

TCIII AVD

Comment by PacificBots on January 5, 2015 at 1:31pm

@TCIII

I originally was going to go with either a stainless steel or brass shaft. But since the shaft needed to be solid, the weight was too much. 

Comment by David Boulanger on January 5, 2015 at 2:02pm

Pacificbots,

You may want to consider a hollow brass shaft with a carbon fiber insert. Super strong and corrosion resistant. 

Regards,

David R. Boulanger

Comment by Petrus Botha on January 6, 2015 at 12:13am

I had pretty much the same idea to launch a vessel to travel from Cape Town to travel to the Prince Edward Islands (Marion Island) and back but dropped the idea due to cost and knowing how treacherous the Southern Ocean can be

I admire your ambition and wish you the best of luck

Comment by Rustom Jehangir on January 6, 2015 at 9:35am

@PacificBots

This looks great! I have a couple questions.

Have you done the "bucket torture test" with your trolling motor? If so, how'd it go?

How do you plan to manage power? Will you run the motor at night or drift?

What happens if it flips over? I'd be particularly concerned about this because the hull is pretty narrow.

We've been on and off for a long time on our SolarSurfer, which is very similar in size, solar power, and goal. We've done a few tests in the ocean and run into a few issues that you might want to consider. We did not have enough power to run at night and our progress was basically erased each day by the drift at night. We added a lot more battery power and solar power but haven't had a chance to test again, plus the days are very short right now.

Our last test was supposed to run for a few weeks but was cut short by seaweed snagged in on of the thrusters. Do you have any plans to mitigate seaweed entanglement?

I wish you the best and will be following the project!

Best,

Rusty

bluerobotics.com

Comment by PacificBots on January 6, 2015 at 11:19am

@Rusty

I actually am looking at your thrusters for another project I have. Congrats on a successful Kickstarter Campaign!

Now that rover does skid steer, I can think about dropping the rudder on the next build!

Capsizing:

Edgar (this craft needs a name, so I am naming it after my father who served aboard an aircraft carrier)  has a trolling motor that hangs down about 36" from the bottom of the boat. I estimate the weight (right now) at about 100lbs, I am working on getting some of the "fat" out, if possible. The motor at the end of the shaft weighs 16lbs. The hull is 21" wide and has a convex deck. The section that supports the weather station and nav light is filled with aeromarine floation foam. The Hull as well is completely filled with flotation foam that will be poured around components.

Seaweed:

One of the benefits of getting a trolling motor is that the propellers are "designed" to cut through the seaweed and muck from close to shore fishing. I did some empirical tests with my intex mariner 4 and was amazed how it chopped through the crud. 

Power:

One of the reasons I went for a jumbo and prohibitively expensive 100ah LIFePO4 battery. The plan is to have the engine and rudder silent during the day as the solar panel will charge the battery. At night the motor and rudder will activate via web commands. Right now I am figuring on three to four hours under power. All electrical systems (except ruder and engine) will remain on 24x7. I managed to get the amp draw down to around .5 Amps during the day and .75 Amps at night. The Nav light is LED and comes on automagically all dusk. Amazingly it only consumes about .25 Amps has 360 degree coverage and has two mile visibility. LOVE LEDs.

In the event that the battery goes below 10.25 Volts the system is designed to shutdown. Once the battery is at 13 volts the system will reboot and continue. 

Staying on course:

Since the motors/rudder will only be assisting in propulsion and steering, I have charted a course along the current. I did a couple of simulations where i tried to make a straight line for Hawaii and it never worked. Once I plotted a course to follow the currents about 50 miles out from the California coast and then a right turn near the tip of baja it appeared I got more a less a free ride across the pacific and approached Hawaii from the south. Once I got close to Hawaii I would deorbit out of the current.

Comment by Rustom Jehangir on January 6, 2015 at 11:34am

@PB

Thanks for all the answers! You've clearly put in a lot of thought and done a good job.

I'm surprised that you are only planning to be under power for 4 hours a day. What continuous power draw do you expect while running? What speed? Since drag through the water is proportional to the velocity squared, I think it is generally better to travel slow and steady versus short bursts of higher speeds.

During our first two tests we used a power management scheme that would basically keep the battery topped off and use all available solar power. The speed of the motors followed a sine curve based on the sun's position during the day. We only needed a small battery since it was only there to power the electronics at night and act as a buffer for the solar power. I imagine that you could eliminate your "prohibitively expensive" battery if you traveled during the day instead of night.

All of the power management was done via PID controller that constantly adjusted power to maximize power output. That also allowed it to work really well on both sunny and cloudy days without our help.

Also, what satellite radio are you using? Have you built the web interface for control yet?

Regards,

Rusty

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