Jump to content

DerekF

942 views

I got out Monday for a first flight for my digital flight control system.  Overall it was a big success!  The one thing I cut corners on to get out there was fully waterproofing the servo.  I felt that the likelihood of a turtle capsize was low (my last one was months ago).  Of course, what did I do after 90 minutes out there?  Turtled the boat and killed the servo--HAHA!  But still a great day with lots of learning and successes:  

1) Being able to "arm" the system at the press of a button was a major convenience.  When the system is "not armed" it is as if the wand is all the way up and in non-foiling mode.  In the armed state, the boat will try to fly at the desired altitude set point.  Sailing off the dock and around the marina where you really don't want to foil is super easy.  No more swimming out to the spirit to adjust ride height!  Furthermore, adjusting altitude and other parameters was easy with the key fob switch.  The LCD could have been easier to read, but it worked.  

2) The electronics enclosure really is waterproof!  After a tough turtle recovery, the electronics survived DRY after 3-4 minutes submerged in about 12 inches of water!

3) The servo is NOT as waterproof.  After the same submersion the servo continued to work for another 5-10 minutes before water ingress fried the circuit board in the servo.  Thankfully these are $40 parts and available with 2-day shipping.  There are lots of tutorials on how to waterproof servos.  I plan on doing so prior to my next flight test.

4) Control loops need tuning.  Things worked out on the water but the control loops felt like they were always behind where they should have been.  I can see it in my data collected and it can be seen in the videos (below).  After an hour of tuning with the wireless key fob, I was starting to get close to the performance I wanted.  Thinking more about the wand if it were a PID controller (Proportional, Integral, Differential), it will have a P = infinity and I = D = 0 (yes, I know I'm ignoring the mode where the wand is just fluttering on top of the water, but let's keep this simple folks).  That leads me to believe, I will need to really crank up my P constant (currently set at 9.0).  I think the I and D constants will be helpful for improving performance beyond the wand, but I'd like to duplicate what I have first.  

5) Epic data collection!  After 90 minutes of floating and foiling I have 5MB of CSV data on heel angle, pitch angle, altitude, smoothing params, PID params, acceleration in X, Y and Z axes, battery cell voltages, etc.  This data will help me tune control loops on shore.  My first guess at constants was made by watching our UFO videos frame-by-frame and estimating elevation and rise/sink rates.  My new data is at 20ms resolution and will give me a much better shot at getting things very close on shore before I head out next!

6) Battery life will NOT be an issue.  After 1.5 hours of foiling I had better than 85% of the battery left.  On prototype #2 I will definitely go with a smaller battery to cut costs and reduce size / weight).  Either way, I have hard numbers on cell voltages vs. time and will accurately be able to calculate how much battery capacity will give me how much time on the water.  

7) I need a hard-reset switch on the boat.  The ultrasonic altimeter I am using is a cheap one from a car bumper.  Occasionally it gets noisy and needs a reset.  Having a way to do a full power cycle on the water short of taking the lid off the enclosure would make resetting the altimeter easier.  In the long run, I will be looking for a higher reliability part for prototype 2.     

 

 

  • Like 1

2 Comments


Recommended Comments

After I made a post (2491) of the  UFO thread that included mention of my "small tri test platform", Derek posted

I'd love to see photos of the Tri you referenced back out on the water this summer!

Discussing a "digitally enhanced" version seems to fit here better than there

I am confident it would not be this summer for multiple reasons.  My current focus is to put in the time needed to get competent at flying my UFO.  Secondly, the tri will never sail again without lots of work.  And thirdly, I really think it would be better to give Derek some time to work out any bugs from his system before I jump in.  The fanciest digital control type device I have ever built is a simple PID temperature controller for my bullet casting pot. 

Now as to my previous "small tri test platform", I posted about it at the time over at https://www.boatdesign.net/threads/small-tri-test-platform.51551/ 

Some advantages were:

  • It was very light weight (I could physically pick up the entire boat - rig and all).  It was too bulky to carry, but I could lift it and spin it around if desired.

  • If needed, I could carry the disassembled boat through "people only" access points in half a dozen trips.  This allowed me to assemble everything down on a beach at locations never intended for boat launching.

  • It had 3 point kick up foils.  My sailing gave me more than a few chances to confirm that the kick up features worked well. 

  • In low/no wind I could make good headway with all three foils kicked up and using a paddle (the boat had very low water friction / wave resistance).  

  • When I wanted to take it easy or do something other than steer and trim, it was simple and effective to set the boat on a heading, cleat off the main sheet, sit on the tiller and just cruise along with both hands free.

  • Having either ama foil broach the surface merely resulted in foil ventilation with rapid loss of boat speed but never close to nose dive or loss of control. 

The shortcomings were many.  They included:

  • The rig was crude

  • The hull was not durable

  • It was "foil assist" only.  The foils gave great roll stability at speed, but that was all.

  • The front foils had no vertical surfaces and did not work well for making upwind headway at typical speeds.  For this, it did better with a lee board placed in service.

If I were to go for a "version 2.0" I probably would want a full scale effort.

  • I would probably cut the hull in half at the widest point.  Then I would split the front portion of main hull.  I would apply apply a thin layer of fiberglass to the inside surfaces of the hull to improve impact resistance.  I would add a section to increase the length from 11' to at least 13'.    

  • The original front foils would be retained but reworked to have some form of active ride height control for full foiling.  Pivoting the entire foil for AOA adjustment would probably be easier than using flaps.  If used, foil pivoting would be implemented such that there would be near zero "slop" and very low friction.  I think a two channel digital control system could make it work.  

  • I liked the function of my original planing amas, but they were just slapped together to see if the concept would work.  All new amas would be part of the plan.  

  • I would be tempted to adapt and use my UFO rig.  

  • The T foil rudder worked but needed minor improvements.  Better AOA adjustability and better bungee controls set up to keep it full down or full up as desired

 

Link to comment

The tri project sounds super cool.  Did you do the entire thing yourself out of fiberglass / carbon fiber?  I like the concept of kick up foils.  The beach landings on the UFO in high wind are always stressful.  On the flip side, I love that you can paddle the Tri if need be.  There are plenty of times, I am running out of breeze and a ways from home that make me nervous by myself on a big bay.  I can remember being in a dying breeze and having a mile to get home against the current.  I stared at my GPS all the way home telling me I was going 0.5 knots--I made it home but that was not fun.  

Were your goals simply to design your own boat or did you have dreams of starting a boat-building company?  Launch a class?  With my digital flight control system, I am really in it for fun.  If it turned into more than that, I'd be thrilled, but I'm keeping my expectations low.  I have started a few tech companies before and never gotten them all the way through to a big exit--and hardware tech companies are capital intensive and require manufacturing and distribution.  

If you ever decide to take it up again, let me know.  I'd love to consult on the electronics.  I am learning a ton from the DFCS project!

Link to comment
Guest
Add a comment...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...