Instructables

Is there a better way than gyros and compass?

Hi All,

First of all I'll describe the project I'm working on Then I'll Highlight my probelm

1) Description:
    - Now There's a boat travelling on a river. There's a satellite Receiver on the boat so passengers can watch T.V. While Travelling.
The river is not straight and there're situations where the boat needs to turn 180 degrees. What I was trying to do is to have a gyro or compass beside the Satellite Receiver and detect when the satellite is not pointing to the right direction (due to the boat going on cureves & turning 180 degrees) and undo that rotations so I can keep the Satellite receiver pointing to the right direction ('cause if not so then they'll lose signal and No T.V any more :()

2) The Probelm:
   - I tried to use Gyro ArduImu V3 but the readings aren't helping much .. some times it's wrong and the yaw drifts a lot :(
   - I tried to use compass but it's not tilt compensated .. meaning that if the compass is n't on horizontal position it'll get different readings! and when they pass below some high Power Electrical lines the compass Gets crazy :(

I hope you got the description & the probelm. Is there anyway else to do it? Or if there's any recommendations I'll be grateful :)

Thanks in advance anyways 

kind Regards
---
Ahmed

It seems like something like this must already exist, and also be sold, somewhere, so why not ask Google(r) if it exists, if I can guess the words others are using to describe it.  I tried:
http://www.google.com/search?hl=en&q=moving+boat+mount+satellite+dish+alignment 

and in the text of this page
http://satellitedish.com/cata0054.htm
I found this quote,

 "[T]here are basically 3 different types of portable satellite systems.

    #1 Work it when you stop. (Parked / Docked manually locate the signal.)
    #2 Stop and Push a Button. (Auto Aiming, Self Aligning at the bush of a button once parked / docked.)
    #3 Fully Automatic and auto tracking Underway or Driving. (No buttons to push. Never not working - fully automatic / full In-Motion.)"


What you want is number 3, right?  The boat is constantly in motion, and you want the dish to continuously align itself.    Some of the dishes sold on that page looked like they might be what you want, although you'll be able to discern that better than me, since you know which satellite and which band you need your dish to receive. 

By the way, it may be the case that buying one of these (type 3) will be much, much more expensive than the stationary kind, so that you may still be wondering about the underlying method, how it works, and is it possible for you to make your own.

Regarding method, I am pretty sure the alignment method that will work best is what Steve was describing, a servo loop,
http://en.wikipedia.org/wiki/Control_system
that watches satellite signal strength and feeds back on that to align keep the dish aligned. 

Although there may also be some direction sensing hardware too (like gyro or compass), because when the signal dips, I think it would help to  kind of have a good guess at what direction, to move the dish, is needed to correct the dip.  It seems like otherwise the controller would do a lot of "hunting", you know, temporarily pointing the dish in the wrong direction just to feel out the signal strength. 


tdk4 (author)  Jack A Lopez1 year ago
Thanks for the Effort ^_^

I tried to google it but I didn't know what to search for :D

but yeah number 3 is what I want and it's really expensive as u said ^_^ So We tried to make our own .. well it won't be high quality product, and the high quality one are overqualified for our purpose!

Yes I guess I'll consider that option beside the GPS one. & I may combine them both. As the GPS support here in Egypt isn't strong enough to rely on it :D

Thanks all for the efforts :D You're Awesome :D
iceng1 year ago
GPS knows which way you are facing ( ie the boat is pointing )
including a compass.

Averaging ( 30 boxcar readings ) puts you  within two feet
last time I heard.

We go on Rally  ADventures where the GPS is preloaded to direct our
car on every turn of a mountain dirt road system.
The instrument can tell you if you are two feet off a predetermined travel line.

A

tdk4 (author)  iceng1 year ago
I'm really feeling so silly that I don't understand your suggestions so far =/ But I'm googling :D

Thanks for the suggestion though ^_^
tdk4 (author)  tdk41 year ago
Doesn't the GPS give u ur current position? how will you know your current heading? or you do that programatically?
Is there any link or instructable I can start from?

Thanks again
iceng tdk41 year ago
Holding my GPS,  I take two steps in a direction and the screen
shows my direction by simply comparing where I am now to
where I was a moment ago ! !

This technique of direction also gives distance traveled
and if you have distance traveled even Up or Skiing down hill
all you need is time and it can give you velocity !

Our mountain game was to set our GPS to record maximum velocity
and then jump over a snow cornice to see who of us could go
the fastest. 
Interesting those who got the most air lost ( were slower ) then we
who kept our ski edges to the hill on the way down !

There are electronics places that sell GPS to computer receivers
that you can use as an antenna pointer or buzz drone to deliver a
toy plane with a message to someones office fourth rt window on
the 23d floor :-)

A
GPS.jpg
I have one of those as well.

Don't forget the spare battery though!
Especially on 48hr treks and we had two additional more evolved units.

With additional batteries of course :-)
frollard iceng1 year ago
GPS can only tell heading if you're moving. Might be okay if you're a slow moving boat with little jitter error on the gps.

GPS+3d magnetometer+ 3d gyro can be used to great success to cancel the yaw jitter - important to take the 3d into account
iceng frollard1 year ago
We are heavy into geocaching here in NV, CA and OR.
And GPS gives accurate high speed car info anytime we have
four or more satellites on line even where there is no cell coverage.
 
I agree you can expect great success with a GPS+3d magnetometer+ 3d gyro !

But the OP may not need 1/2 degree resolution for his antenna pointer
I would by inclined to use an XY or XYZ  signal strength servo and lone GPS
as my first attempt.

And what kind of people get on an excursion river boat and then watch TV ?

A
tdk4 (author)  iceng1 year ago
http://www.alarabynews.com/wp-content/uploads/2012/10/%D8%B1%D8%AD%D9%84%D8%A91.jpg

That kind of boats :D

Thanks A lot Guyz ^_^
iceng tdk41 year ago
ok I get it :-)

They have kids and you can't see much at night.

Is that a real paddle wheel ?

You might be better tracking the signal strength and keeping that maximum. Are you controlling the dish in azimuth and altitude, or just azimuth ?
tdk4 (author)  steveastrouk1 year ago
Well I didnt know I can do that in the first place :D
but If I can track the signal strength .. and the signal gets weak .. How will I be able to get it stronger? on which basis I will move the Dish?

I'll start googling how can I track the signal strength though .. :D

Thanks for the quick reply ^_^
Put a servo loop around the signal strength, and base the tracking function on a maximum power point tracking method.
tdk4 (author)  steveastrouk1 year ago
Ok I'll investigate your suggestion and reply when I reach a dead end ..
your suggestion is completely new to me so if you can suggest a place where I can start from in my search?

Thanks again
tdk4 (author)  tdk41 year ago
How Can I measure the strength of the signal? Is there a device or sensor. googling isn't heping much when searching for something I don't know =/

Thanks again.
"Satellite signal strength meter" - also some receivers can be asked what signal they are receiving, over a serial port.

Steve
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