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[on:]

I'm planning a new project. I'm planning to make a 4 motor, 2 axis copter(like the silverlit x-ufo).
I've ordered in one motor, esc and connectors, just to see if i can get enough throttle.
Theoratically, I should get a total of 14 kg throttle(3.3kgx4motors). I've come up with a couple of problems of which I have to solve. Havent got any parts yet.
Using a gyro with a numeric integrator i would, i think, get a drift, because the sample-period would be to long. but I don't know for sure.
It will be a fairly large program, so I guess the sample time would be even greater than e forsee.

Most of the problems are already solved, but the tilt-measuring is still a problem.

Anyone have a suggestion of what to do ?
If there is a different hardware for tilt measurement, I am all ears.
If not, how do i get a gyro to measure the correct angle over a longer periode of time. with no drift.
numeric integrator:
angle = angle + W*sampletime; //W = angle-velocity.
values in the integrator will be scaled, so that 0 degrees = 0, and a positive angle gives positive W, and negative angles give a negative W. so that 0 degrees ---> angle = 0.

Thanks for all help. Daniel.

[Reply #1 on:]

Theoratically, I should get a total of 14 kg throttle(3.3kgx4motors). I've come up with a couple of problems of which I have to solve. Havent got any parts yet.

Holy Cow - 14 KILOS?  How big is this puppy going to be?

Using a gyro with a numeric integrator i would, i think, get a drift, because the sample-period would be to long. but I don't know for sure.
It will be a fairly large program, so I guess the sample time would be even greater than e forsee.

Most of the problems are already solved, but the tilt-measuring is still a problem.

Anyone have a suggestion of what to do ?
If there is a different hardware for tilt measurement, I am all ears.

for measuring tilt an accelerometer would be my choice.

[Reply #2 on:]

thaks for answering.

14 kg is like an assumtion of what the actual throttle is going to be. 3.3*4 is actually 13.2kg. that is with an ideal propellar and ideal powersupply(LiPo batteries).
I guess the frame size will be 75-100 cm across. i guess probably something like 75cm*75cm.


I was playing with the thought of using accelerometers, but since this is a dynamic object, which has an dynamic acceleration in addition to the "acceleration" the tilt wil give out, i would rather just use something to measure just the angles. an accelerometer will probably be used to measure the initial angles of the copter, because the intergrated gyro will have a logical 0 angle at the initial state of the copter. so if the copter is not totally horizontal both axes, it wont know what is horizontal.

I really suck at explaining so sorry if it makes no sense.

[Reply #3 on:]

I was playing with the thought of using accelerometers, but since this is a dynamic object, which has an dynamic acceleration in addition to the "acceleration" the tilt wil give out, i would rather just use something to measure just the angles. an accelerometer will probably be used to measure the initial angles of the copter, because the intergrated gyro will have a logical 0 angle at the initial state of the copter. so if the copter is not totally horizontal both axes, it wont know what is horizontal.

Ah, good point.

simple question now: I have a small electric helicopter that heeps iself pretty level with no help from me.  Just balanced and it hangs from the rotors I guess.  Is there anything in that?

This post might get more responses in a hardware area by the way - not sure how you'd get it moved though.

[Reply #4 on:]

I can not believe the stuff you can buy these days!  You probably know you can buy two axis gyros from sparkfun but i would never have dreamed it.  In their writeup it ref's RC helicopters so it must be a well-known application.  Maybe you could fire a question to their customer support or see if they have a forum you could post in.

http://www.sparkfun.com/commerce/product_info.php?products_id=700

[Reply #5 on:]

simple question now: I have a small electric helicopter that heeps iself pretty level with no help from me.  Just balanced and it hangs from the rotors I guess.  Is there anything in that?

I think you are right. it also have the tail rotor to keep it from spinning the opposite way of the rotor. that same rotor can turn the copter around its own axis(which goes through the center of the lift rotor).

This post might get more responses in a hardware area by the way - not sure how you'd get it moved though.

I think i've found a way, so I don't really need help no more. I think.
Can just leave the post open, just in case anyone have something.
Thanks for your help.

I can not believe the stuff you can buy these days!  You probably know you can buy two axis gyros from sparkfun but i would never have dreamed it.  In their writeup it ref's RC helicopters so it must be a well-known application.  Maybe you could fire a question to their customer support or see if they have a forum you could post in.

That is one cheap gyro. but looks like it does'nt got any electronics on it. then its worth paying a couple of dollars extra to get it all on one board. But thanks. It would have been great to use with the project:D

[Reply #6 on:]

Sorry for necroposting, but this is something that has been on my mind for years. 2 years ago I actually took a broken Silverlit X-ufo and put a Attiny2313 in it and read my usual radio transmitter from it and converting it to the quadcopter matrix of control of the 4 crappy DC-motors on it. It flew... but straight to the ground because it had no sensors at all   The control matrix was good though.

However, I've been checking in to the Mikrokopter project (https://www.mikrocontroller.com/index.php?main_page=index&cPath=69&language=en and http://www.mikrokopter.de/ucwiki/en/MikroKopter/ ) for a long time. It uses 3x ADXRS610 (rate gyros) in X, Y and Z and also 1x 3 axis accelerometer in conjunction with those.

What I want to know is if anyone else has some experience with these sensors (gyros/accelerometers) and the quad-copter/rotor as a base, and the Arduino platform? I'm probably gonna try the first movement sensor I get my hands on on my Silverlit base, then go over to brushless, and maybe add Sharps' IR distance sensors to make it uncrashable (or as good as) for indoor flying.

[Reply #7 on:]

You might find useful stuff over at DIYdrones, and the home of Arduipilot, an Arduino-based model aircraft (or model craft) autopilot:
http://diydrones.com/profiles/blogs/ardupilot-main-page

I know a couple of years ago, they were experimenting with helicopters.

HTH

[Reply #8 on:]

I am interested in Arduino autopilot, but it and a plane is a bit too much money for me right now

I saw a new one at Sparkfun
http://www.sparkfun.com/commerce/news.php?id=354

It has got an ATmega1280  ;D
Glerk!