SparkFun Forums

[thirdmate]

hello. i am working merchant cargo ship and i want build a internet satellite tracker system.
in voyage, gps send istant lat/long data and compute internet satellite elevation and azimuth later gyro imu fix this data. finally this data go to servo motors and focus to satellite all time.

here is lat long and satellite elevation and azimuth finder.
http://finder.tooway-instal.com/fixe/pages/index.html
here is gyro imu.
https://www.sparkfun.com/datasheets/Sen ... DOF-v2.pdf


i wish explain myself well.
how can i make this program? any advice? which is recommended. arduino or rasperry pi?
best regards

[stevech]

Independent of ship's systems?

Most ships have an AIS system aboard. Some send GPS location via Intelsat to terrestrial networks.

https://www.marinetraffic.com/en/

In many countries' territorial waters, AIS is mandated by law.

Service from Intelsat is rater expensive.

[Mee_n_Mac]

See this thread;
https://forum.sparkfun.com/viewtopic.php?f=42&t=37509

You don't need the IMU, you do need to know your location and heading. Tilt compensation for ship's roll might be nice-to-have but on a cargo ship, perhaps unneeded.

How do you intend to get location and heading ?

[thirdmate]

i find solutions.

i want to explain myself.

first i need compass and gyro imu and i need gps. i need to know geographic coordinates for calculating satellite azimuth and elevation.

ship is moving and meeting rough seas. i want to build motorized gyro and using Kalman calculate system.

and soon.
gyro imu: for motorized gyro for antenna(i need stabilize place for antenna at rough seas)
gps: for calculating lat/longd
arduino uno: calculating elevation and azimuth.(like sun tracker. only different my object is internet satellite.
arduino uno: controlling gyro 2 servos using gyro imu and making stabilize place for antenna. and arduino must be control other 2 servos for moving antenna up and down(azimuth) and right and left(elevation)

i wish to explain myself.

by the way, i build the system in my head. now i will do and i write here again. but also i need recommend/help all time. i hope to explain myself.


best regards yo.

[Mee_n_Mac]

by the way, i build the system in my head.

Out of my head and into JPEG. I'm not sure you need an IMU, perhaps a pair of gyros if your ship rolls more than 1/2 an antenna beamwidth. I put a PC in because it's where you showed the satellite information resided. You also need to solve the problem that hobby servos don't rotate a full 360 deg.
(click on to open)

SatAntennaPointingBD.jpg

[thirdmate]

Hurray! you ar good man yo. thanks for attention and jpeg. yea we meet sometimes rough seas.example roll. if ship meet rough sea rolling 2 second or 3 second 20 degress starboards side and later 20 or 15 degrees port side. and my system must work all type wheather. and i need stabilized place for satellite antenna. therefore i need these: gyro for using kalman filtering for stabilized place.
here the video
https://www.youtube.com/watch?v=T0SFAdPUUYs

later this stage i need 2 servos more for antenna azimuth and elevation control.

this antenna tracker without gyro and gyro controlled servos. its contains 360 degrees turning servos.

http://api.ning.com/files/swLlbX5ug5ZF6 ... ?width=750

later this stage i need calculate KA-SAT satellite position.

here satellite elevation and azimuth finder page

http://finder.tooway-instal.com/fixe/pages/index.html

this page need latitude and longitude information and calculate antenna azimuth and elevaion.

my lat long information send by gps to arduino and arduino with this script calculate elevation and azimuth values forward to servo antenna motors(360 degrees)

and gyro imu send information(xyz axis) to arduino and kalman filtering script calculate and send values to gyro stabilizing motors.

in the end this system all time tracking satellite even ship meet hardcore seas.

is good that.? did you see any problem please reply again. this project is very important for me. and i need good servos.

i must ask this question. my gyro stabilizer motor how much weight can carry. because i must use 120 cm parabolic antenna(aluminium) and LNB, BUC, Feedhorn vs satellite equipment. and gyro motors must be carry these parts weight.

and as you know i use 4 servos. arduino using 7 volt and i need little bit more powered servos. example 12volt.

is it problem for my arduino? i want to powering servos externally. i think its possible.

thanks so much again for your helps.

best regards.

[Mee_n_Mac]

i must ask this question. my gyro stabilizer motor how much weight can carry. because i must use 120 cm parabolic antenna(aluminium) and LNB, BUC, Feedhorn vs satellite equipment. and gyro motors must be carry these parts weight.

You are correct to worry about the weight. But even more important are the balance and moment of inertia(s). I don't know what's available in a hobby servo that would suit your need. You'll have to come up with a ballpark figure for the moment of inertia for each axis to know. You also need a good mechanical design or resonances in your platform (and base) may make your control loop unstable. How well do you know control theory ?

and as you know i use 4 servos.

Why 4 ? You only need 2. And why complicate things with Kalman filteringing ? It's not needed either. All you're trying to do is stabilize a platform in 2 axes. To keep it pointing at the sat within +/-2.5 deg (the beamwidth of your 120 cm antenna @ 30 GHz). Roll (of the antenna) doesn't matter as the RF is circularly polarized.

arduino using 7 volt and i need little bit more powered servos. example 12volt.
is it problem for my arduino? i want to powering servos externally. i think its possible.

You will need external power for your servos. The Arduino will only calculate and output the control signals.

Now for some more questions;
- Where are you getting the position and heading data ? From an additional GPS and compass or from the ship's systems somehow ?
- You posted a picture of a 2 servo platform with antenna, etc. Is this yours or something different ? It's not well balanced.
- I will guess that you might end up making your own servo; buying separately the motor, controller and encoder. Would you be capable of that ?
- I assume you know the regions that KA-SAT covers. Does your ship run in the littorals of those regions ?

[thirdmate]

hello again. sorry for delay but i am going to voyage..

1- if i use hi power servo(not too much ofc), servos can carry antenna system and i found pololu site and i find 360 degrees servos.

2-i think 4 servos more critical lock to satellite. cuz big system and expensive systems have gyro stabilizer.

and your questions

1- i get to data this gps. not ships gps. but if i want i can get the data from gps system. because in past i take data from ship gps.
2- picture is not me. i found in internet. googled. antenna tracking.
3- in past i study computer programming school. but i left school 1 year later and i go maritime school. so i am not so irrelevant to programming. i trust myself hehe. and i like too much internet. in internet everything is can be found. internet connect us and our knowledge. and my childhood friend is computer engineer. he help me sometimes.
4-yeah my ship is working gibraltar to suez and blacksea region.
5- our ship is going now ukraine to italy. i can bought arduino in italy. i can found easly.
6- in voyage i work this project(buying seperatly parts) at odd moments.

i hope i built this system.

best regards

[Mee_n_Mac]

1- if i use hi power servo(not too much ofc), servos can carry antenna system and i found pololu site and i find 360 degrees servos.

If I were doing this I would probably make my own azimuth "servo", really just a gear motor driving a bearing ring (or maybe a motor with a pulley using a belt) with a position encoder on the rotating ring (aka the azimuth platform). I would do this because the vertical mast and Az bearing must carry the entire weight of the rest of the system and do so even in a big storm w/o breaking (let alone still keep tracking). I'm not sure what servo's you can buy that would have the needed bearing strength. Have you looked at the systems Servo City sells ? Some of those are pretty strong. It needs to rotate the entire 360 degrees, ideally more (I can explain). This servo needs to be aligned with the ship, perhaps so that an Az servo command of 0 deg makes the antenna point dead ahead relative to the ship's bow.

On top of that rotating ring (the Az platform) you would put the elevation servo and platform. This servo only needs a range of perhaps 100 degrees (my GUESS). Balancing the weight of the antenna, LNA, BUC and other stuff about the servo's axis of rotation is important, otherwise the El servo will always be "on", fighting gravity to point the antenna. The strength (torque) and speed of the motor needed depends (as does the Az servo motor) on the moment of inertia of the antenna, LNA, BUC and other stuff and how fast the antenna must move to stabilize the antenna despite the ship moving beneath it. I suspect that the ship rolls faster than it pitches or yaws and so the El servo must be able to move the antenna, LNA, BUC and other stuff perhaps 1.5x as fast as the fastest roll rate. And it must accelerate (go from 0 deg/sec to maximum deg/sec) faster than the ship does. The acceleration the servo can provide is determined by the motor's torque and the moment of inertia.

Now if this is all sounding more complicated than you care to know ... then perhaps this project isn't for you. OTOH if you want to learn about servo systems and space stabilization, this is a jumping-into-the-deep-end way of doing that.

So before buying servos and platforms, you should weight the components you have and calculate the elevation and azimuth moments of inertia. Just having a good idea, say +/- 10% of the true values, is probably good enough.

http://www.servocity.com/

2-i think 4 servos more critical lock to satellite. cuz big system and expensive systems have gyro stabilizer.

You are building a gyro stabilizer. I still don't understand why you think 4 servos are needed ... or wanted. You might use 2 motors, in parallel, to drive either the El or Az platform, but there should still be only 1 position indication for each axis ... so that 2 motors and 1 position indicator gives you a single (strong) "servo". If you try to use 2 separate servos to move a platform (let's say the elevation platform holding the antenna, LNA, BUC and other stuff) the servos will not agree with each other's position and end up "fighting" each other.

[Mee_n_Mac]

1- i get to data this gps. not ships gps. but if i want i can get the data from gps system. because in past i take data from ship gps.

So can you get GPS info from this ship ? If true then that eliminates one thing you have to buy and have to mount outside someplace and run an antenna cable to. Plus I suspect the ship' GPS is better than than one you could buy. You have to decide what is easier for you to do.

How about a compass ? A GPS will give you ship's heading when underway. Heading is not EXACTLY what you want but may be close enough to work. But GPS doesn't work when not moving. When not moving you need a compass to get the ship's bearing to magnetic North (again not EXACTLY what you want but it can be turned into what you want). I assume you want this to work when not underway. Getting an electronic compass to work on a metal ship is very hard to do. If you can get the ship's compass info, I recommend that you do so.

3- in past i study computer programming school. but i left school 1 year later and i go maritime school. so i am not so irrelevant to programming. i trust myself hehe. and i like too much internet. in internet everything is can be found. internet connect us and our knowledge. and my childhood friend is computer engineer. he help me sometimes.

OK, it would be better if you friend was a control systems engineer but you have what you have. You may wish to read just a little about control loops and feedback (in your native language) so what I say makes some sense to you.

FWIW a "servo" is one example of a position control loop. The controller (perhaps an Arduino) sends a position command to the servo in the form of a pulse, the width of that pulse tells the servo what position to go to. The servo is actually a gear motor driving an output shaft which is also connected to a potentiometer. The potentiometer tells the servo electronics where (what position) the shaft is at. The electronics in the "servo" compare the command to the position and tells the motor to turn on, how fast and in what direction. The motor runs in the proper direction until the measured position (via the potentiometer) equals the commanded position (or close enough). That's a position control loop, all contained in a box you call a "servo".