Project - Roboard for a QuadCopter

[Sketch]

Hi,

Im using a Roboard to be the onboard computer for a quad rotor helicopter.

This is sort of an ambitious project for my friends and I. I am running Ubuntu 9.04 on the roboard

As of now i have it setup to read my keyboard input and send continuous PWM signals to a brushless speed controller ( using rcservo library, anyone have experience with the pwm library? ), and read an IMU on the rs232.

eventually it will also have a sonar sensor for altitude sensing and a laser range finder for mapping and obstacle avoidance. As well as wireless communication with a "mother ship"

I am a complete Noob when it comes to this, when i started this 3 months ago i didn't even know what Linux was.. ive been googling and hitting the forums furiously to get where i am now and would very much appreciate any guidance with this project.

So i was wondering has anyone used the roboard for controlling brushless motors, or is trying to do anything similar to this with the roboard.

[limor]

Hi Sketch

we don't see many flying robots around here probably due to the great challenges and millisecond closed loop control reactions needed to ensure the expensive flyer doesn't disintegrate. walking robots seems hard enough..
so your project is of much interest.
Have you managed to figure out how to use the pwm output to control the brushless motors?

[snest]

Hey Sketch,
I am attempting the same thing. Keep us posted on how your progress is going, perhaps we can serve to help each other out.

Good Luck!

[Flid]

PWM signals to a brushless speed controller is not enough fast you must use I2C bus to control your brushless motors

Look for MikroKopter with google

If you speak French you can go on my website www.mk-fr.info

[matt.stevenson]

For a good quadcopter, how fast do the motors need to respond? I'm sending PWM commands for all servos wirelessly using Java every 50 msec.

I'm sure that could be much faster for a quadcopter that doesn't need to receive commands over wifi.

Would 10-20msec be fast enough, or is the problem something else entirely?

[SK]

One of the most successful Quadrotor designs by AscTec (http://www.asctec.de/) uses a 1kHz loop for attitude control (see also http://www.societyofrobots.com/robotthe ... _1_Khz.pdf).
These quadrotors are among the most stable I've seen and are used by a number of research institutions and companies.

[matt.stevenson]

Does anyone know if there is a max speed on the PWM channels, is there any inherent limitation to keep them from reaching these speeds?

[roboard]

Does anyone know if there is a max speed on the PWM channels, is there any inherent limitation to keep them from reaching these speeds?

The resolution of RoBoard's PWM is 20ns and the maximum PWM pulse output frequency can > 3MHz.

[matt.stevenson]

That's very good to hear.
I think I know what my next project will be.

Forget quadcopter, icosikaiteracopter here we come!

Maybe I'll just use 20 motors because icosacopter is so much easier to pronounce.

[Sketch]

wow thanks for the reply, i sort of got disheartened by the complexity of the project, but now im trying again with another approach to it,

use an Arduino based Quadcopter base and have the roboard sitting on it and piloting it, so basically replace the R/C transmitter with a roboad. this way i can have the laser range-finder and a AHRS system on the roboad doing some mapping and video streaming to another computer mothership, sounds like a good plan?

out curiosity, what kind of OS is everyone using, ubuntu? xlinux, im trying to get xlinux because i read that its a real time system which is probably a better option?

[matt.stevenson]

Well I've been happy using Debian. When I tried Ubuntu, the set up and a lot of other things were much easier, but it ate up almost all of the ram.

[snest]

I've gotten Slitaz to work on the Roboard 110. It took awhile to set up initially, but now that I know what to do I am able to set up an installation of Slitaz quite quickly; all of the modifications can be completed in minutes.

[SK]

use an Arduino based Quadcopter base and have the roboard sitting on it and piloting it, so basically replace the R/C transmitter with a roboad. this way i can have the laser range-finder and a AHRS system on the roboad doing some mapping and video streaming to another computer mothership, sounds like a good plan?

Sounds like a very interesting plan, but please be aware that
-getting a working IMU and stabilization for a quadrotor system
-getting a LRF onto a quadrotor and doing something useful with it
-doing coordinated distributed video processing
are each ambitious goals on their own, the closest to what you're describing is probably what these guys did (indoors, which is of course harder than outdoors with GPS):
http://groups.csail.mit.edu/rrg/videos.html

out curiosity, what kind of OS is everyone using, ubuntu? xlinux, im trying to get xlinux because i read that its a real time system which is probably a better option?

Well that largely depends on what you want to do. As long as you have a microcontroller doing the low level, hard-realtime control tasks you probably could get away with only using a soft-realtime system for the Roboard.

[Sketch]

Hi guys,

So Ive started the Quadcopter build, Im following the arducopter build which is pretty easy to follow and setup. Ill come back and post when that is done.

Yes the tasks individually are difficult, specially for someone who is not a programming adept. But I want to keep going...

here is my plan,

Phase 1: get a manually flown quad to fly,

Phase 2: get a 3d Slam algorithm going with the LRF and IMU** (of course this is going to be tough)

Phase 3: Make it autonomous.

Anyone know if The Roboard can supply enough power to a LRF which requres 500ma current.. I read somewhere that it Roboard only provides 400 ma... any solutions to this?

[roboard]

Anyone know if The Roboard can supply enough power to a LRF which requres 500ma current.. I read somewhere that it Roboard only provides 400 ma... any solutions to this?

Hi,

the RoBoard's USB & 5V pin output allow > 1000mA current. So powering LRF with 500mA should be ok.