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Initial Thoughts, Philosophy, and Block Diagram

Ok team, here goes my first blog post.  My goal here is to build a Digital Flight Control System (DFCS) for my UFO using a sonar range sensor as opposed to the wand.  The design needs to completely mimic the performance of the wand system currently in the boat.  The system needs to be fully removable to allow for One Design Racing if desired.  

A few design guidelines...

Improvements to current control system:

1) Sensing wave terrain out ahead of the boat

2) Not engaging the mainfoil flap until the boatspeed hits 7 knots to reduce drag while floating

3) Toggle settings for upwind vs. downwind (maybe a button press?)

4) Data acquisition

5) Auto rear foil rake adjustment (this is a maybe feature, this would be lots of extra hardware for limited improvement)

 

Questions to answer:  

1) Do I need a GPS to get good boat speed or is the accel, gyro, magnetometer IMS good enough? 

2) How and where will I couple the servo to the flap control push rod

3) How big a challenge will marinization be?  Is enough to buy waterproof parts and a waterproof box?

4) Is it useful to have more than two sonar sensors to create an accurate map of oncoming wave motion?  Does wave motion traveling orthogonal to the direction of the boat matter?  Or are waves going so slow compared to the speed of the boat that it doesn't matter?

 

Design Philosophy:

I will endeavour to use parts that have excellent tutorials available online.  

I will be concerned about the cost of my time even when it costs a bit more money to buy parts that are easier to integrate.

 

Basic Block Diagram Below:

https://drive.google.com/open?id=1fPYXJLlrcZufAwTNtmjy9HG_BbAYtpas

 

 

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I have been thinking about this for a while as well. One of the areas where I have evolved a bit is that I worry about a servo and batteries powerful enough to drive the flap mechanism.

Because of that, in my mind practical uses of #1 should be later in the roadmap. It makes sense to start with small simple servo mechanisms that that engage/disengage the wand (your #2) and can control foil rake. A simple mechanism to control wand length (manually or electronically) can also be a winner with modest effort and complexity. 

I would set all these things up, and provide simple manual control -- as SuperFoiler had, buttons on the tiller extension. There is significant work in making these mechanisms work: reliability, failsafe, etc. This stage of work has, in itself, great value and can stand alone.

All the sensor driven work -- GPS, gyro, water distance -- and computer algorithms should be -- IMHO -- second phase.

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Just so I follow your thinking on the wand, are you imagining a system that would raise and lower the wand electromechanically?  It would additionally adjust main foil rake?  Both of those sound like a lot of custom mechanical parts (probably my area of least experience). 

On the servo / actuation question, my first thought was to actuate the flap mechanism by using a piece of wand (1 foot length or so) and link the servo to this 'stub wand'.  Then actuate the main foil flap using the same mechanics already in the boat.  I think this would be simple and totally removable.  It could be made better by using a piezo to directly drive the pushrod that actually actuates the flap but that would require more work and locating the piezo in a different location than the sensors requiring a cable harness.  Perhaps even a hydraulic system could be done as well but again, lots of work and maintaining (bleeding) hydraulic lines is a real pain.  

As far as buttons and LED / display feedback go, I haven't thought that far ahead.  Buttons would need to be somewhere other than the end of the sprit so a cable harness or wireless connection would be required there.  I bought the Arduino Mega so I have lots of IO and processing horsepower for whatever good ideas crop up....

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Wand: a small wheel with grooves, embedded in the piece that holds the wand today. 2 grooves, one for a control line (rope) and the other groove for the wand itself. control line goes to aft end of sprit, can be controlled by hand, or through a servo.

On the servo/actuation front, it might be better to use electronics to "enhance" the existing mechanism, instead of trying to replace it. In other words - what if instead of replacing it, you had means to dampen or strengthen the relationship? This can be as simple as a servo controlling a screw mechanism (ie: a small low powered servo could shorten or lengthen the effective length of the rod that runs inside the crane). 

Buttons should somewhere handy. We can use BT - something like https://www.amazon.com/NIU-Smart-Button-Android-NodOn/dp/B01HOOE6SQ

 

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The first improvement I’d work on making after replicating the existing system (i.e. sonar sensor for current ride height and servo for actuation only) is improving the algorithm. Specifically, the gearing on the UFO is setup to handle waves as well as possible at a slight top speed cost, but with the electronic system it’s easy to automatically adjust gearing. What you want to try is taking lift off the flap faster when ride height gets too high, adding it back faster when boat gets near/in the water and keeping the flap close to neutral at a constant gearing at your desired ride height. someone has already set this up mechanically in a moth: https://avalonsails.com.au/blog/2018/3/14/latest-update-on-the-bugs-cam. The ride height adjusted gearing should make the boat easier to foil and less likely to ventilate. It can also improve top speed by reducing flap actuation and associated drag when you’re stably foiling at your desired ride height. 

My second thought is that boat speed sensors will be a pain, because gps will not give accurate boat speed if there’s significant current. That’s why I think you focus on what you can do to improve the system without boat speed as an input before you add the additional sensors. Paddle wheels are out for speed through the water, because they’re a pain and where do you put it. That leaves ultrasonic speed sensors, but they also need to be in the water, so where do you put it. Best place is probably the mainfoil. You’ll definitely need to find a sensor way smaller than what I’ve seen on keelboats and find a faired way of incorporating it. And You’ll need a second prototype mainfoil to incorporate the sensor and fairing, while still having a one-design UFO readily available. Anyway, my two cents is to get started under the assumption you won’t know boat speed and only incorporate boat speed later. improvements can be made without boat speed data for sure.

-Nick

 

 

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