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Topic: Small two axis servo? (Read 762 times) previous topic - next topic

sug15

I'm developing a small rocket with an inner diameter of about 1.3 inches. I will be using an Arduino to track and guide the rocket. To guide  the rocket, my plan is basically to use a gyroscope to sense when the rocket is not going straight up, and to rotate the rocket motor accordingly. For example, if the rocket starts to aim a little bit north, I pivot the motor inside the rocket south so that the rocket rotates back to going straight up.

How can I do this? So, what I essentially need is a controllable joystick that is fairly robust. I could use two servos, but is there anything better available? If you think I need to use two small servos, what servos would you recommend?

Thanks!

terryking228

Hi, have you googled/researched what other model rocket people are doing?

I think most of them that do flight control use small tabs on the aft fins, or small forward tabs with small servos. This gives guidance that also works after the boost phase.

Can you mount the engine so that it is gimbaled in a way that there is no force needed to tilt it??

With this size rocket, I assume it's solid propellant?

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

sug15


Hi, have you googled/researched what other model rocket people are doing?

I think most of them that do flight control use small tabs on the aft fins, or small forward tabs with small servos. This gives guidance that also works after the boost phase.

Yes, many model rockets that are close to this size do not have any form of control. The larger ones have the controllable fins, which is a possibility for me, but I would much prefer the tiltable motor because it allows me to keep the frame in one piece, is more efficient, and I think it will be less apt to break.


Can you mount the engine so that it is gimbaled in a way that there is no force needed to tilt it??

Yes, that's my plan.


With this size rocket, I assume it's solid propellant?

This is actually a monopropellant liquid rocket (it will be small :p), but with a fuel tank that is not rigidly attached. This should allow the motor to be tilted pretty easily.

terryking228

This is sounding pretty mechanically complex, compared to forward fins.. Where would you mount the servos? Forward or aft of the fuel tank? How would you link them to the engine?

What is the run time of the engine?  It'll be HOT back there.

What's the current possibilities for a Monopropellant motor? Ethylene Oxide?  I hope not NitroMethane.  (My high school got a visit from Guys In Suits after a newspaper article about my friend and I building a CH3NO2 based engine).
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

sug15

#4
May 30, 2012, 10:35 pm Last Edit: May 30, 2012, 10:40 pm by sug15 Reason: 1

This is sounding pretty mechanically complex, compared to forward fins.. Where would you mount the servos? Forward or aft of the fuel tank? How would you link them to the engine?

What is the run time of the engine?  It'll be HOT back there.

What's the current possibilities for a Monopropellant motor? Ethylene Oxide?  I hope not NitroMethane.  (My high school got a visit from Guys In Suits after a newspaper article about my friend and I building a CH3NO2 based engine).

The servos/engine directional control, arduino, and a fuel pump will be mounted between the engine and fuel tank. I should have a good amount of space to play with, so I'm almost positive I can avoid the heat.

The engine runs on hydrogen peroxide and I plan on using manganese dioxide as a catalyst. So, the engine won't be as hot as typical engines, because nothing is burning in this one. I'm not sure how long it will run for. However much fuel I can fit in, I suppose. I'll end up doing some calculations, and slowly run it while monitoring the temperature to be sure.

Ha, funny story about your engine. I'll be careful, this should be relatively safe.

So you don't think there is a controllable "joystick"/2 axis servo out there, do you? What about servos, are there any specific models you would recommend or should I just see what will fit best?

zoomkat

Have you actually purchased the hydrogen peroxide for your project? Your best bet for controlling the rocket is with a standard RC setup. Model rocket forums probably can provide you quick answers.
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

sug15


Have you actually purchased the hydrogen peroxide for your project? Your best bet for controlling the rocket is with a standard RC setup. Model rocket forums probably can provide you quick answers.

No, but I know where to buy it, and I know how to distill my own. Thanks, I will look into that setup and the rocketry forums.

Anyway, now I am considering building a different type of engine, but my same question remains.

zoomkat

Quote
To guide  the rocket, my plan is basically to use a gyroscope to sense when the rocket is not going straight up, and to rotate the rocket motor accordingly


I think a quadrotor forum may have info on gyroscope setups.
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

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