[LMS303LDHC][Wind sensor] Tilt compensation

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michwii
 
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[LMS303LDHC][Wind sensor] Tilt compensation

Post by michwii »

Hi everybody,

I'm having some troubles with my wind sensor =S

My wind sensor may move into space on all the axis (but most of all on the z axis).

I would like to have a tilt compensation on my wind sensor using my LMS303LDHC. Is anyone has already implemented this solution ?
I already checked on the internet and the only tilt compensation that has been already implemented is the tilt compensation on a compass.

http://cache.freescale.com/files/sensor ... AN4248.pdf

If you want to use the algorithm above you need to provide 3 axis values.
The compass has already 3 axis values, although my wind sensor has only one value so their algorithm cannot be transposed.


Could you please help me.
Thank in you in advance for the time you'll may give to me.

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Franklin97355
 
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Re: [LMS303LDHC][Wind sensor] Tilt compensation

Post by Franklin97355 »

If your wind sensor is mechanical there is no way to compensate due to the nature of the sensor. The best you could do is mount the sensor in a gimbal mount to keep it level.

michwii
 
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Re: [LMS303LDHC][Wind sensor] Tilt compensation

Post by michwii »

Hummmmm,

Yes my sensor is mecanical and I forgot to specify that is not a speed wind sensor but a wind direction sensor.

Because my direction wind sensor will be put in a boat they will be some movements that I would like to compensate.
Put the sensor in a gimbal mount to keep it level could be a solution but it means that I have to built it by my own and I'm not sure that I have enought skilled to do it :(

Here is another product (which is electronical) but really expensive (I cannot afford it) that compensate the movement of the sea : http://www.lcjcapteurs.com/product/cv7- ... r/?lang=en

In the description (pdf) it is written : "Stability of sensibility
to light winds - Small wind drag - Efficient with heel angle up to 30°"

Do you think this sensor include a gyroscope ?

Thank you for your answers =D

Kind regards

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wdickenson
 
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Re: [LMS303LDHC][Wind sensor] Tilt compensation

Post by wdickenson »

I once had a similar design for a table that would adust to the sailboats tip. I used a ball from a trailer hitch, a wood socket and two servos, mounted on each side with a long arm. The table was only 24 inches. But I read the tilt switch and compensated via servo.

Not sure it's worth it though. You are looking for apparent wind direction ( and likely speed) and I suspect that the mechanism would be too complex to be worth it. But you can get small ball-links from your local RC store or online. Couple the sensor to the servo and you should be good.

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wdickenson
 
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Re: [LMS303LDHC][Wind sensor] Tilt compensation

Post by wdickenson »

So I did some checking on my own sailboat and I think you may be putting more into this than it deserves. I rigged up a tilt compensated plate and then stuck it on my mast. I had about 30degrees of play and a duplicate (uncompensated) one on my mast. I apologize if I over explain, you probably know all this anyway.

Windspeed was relatively unaffected as you would expect. Yes, there was a minor degradation but it was in the .1-.2 knot range. Heeled at 15 degrees had nothing appreciable over a 10 minute run when compared to my other gauge. Could be more gauge variation than real difference. That would require a ton of additional data.

Direction was a mess after 20 degrees uncompensated for a short time. Beam and broad reaches were the only time I could do it largely because the direction was "up" but ..... as soon as I had significant headway, the apparent wind took over and I was once again getting good readings (as the boat was now moving "into" the wind). So it was only an issue when I came about, not cruising. So when the wind is perpendicular to the sailboat, the gauge was dicey at a dead calm and almost a dead stop. Any speed seemed to correct that.

This morning I put a crude spring pendulum on the platform and only compensated for roll (pitch in my sailboat is too fast and too small). Same results. Any kind of speed got me back to "normal". So not that you asked but the conditions that could cause a problem are only transitory (change in direction, Waves, etc)

However, I wonder if you could put 4 flex sensors on a "whip" and measure the resistance to compute direction and speed all at once. Now this I have not tried this but you might be able to orient them to the boat, read the analog voltage and then assemble a table to correlate to speed and direction. Just a thought.

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