SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jan 17, 2015, 08:41 AM
Registered User
Joined Sep 2014
23 Posts
Discussion
Quadcopter take off problem

Hello to the forum,

I recently build a quadcopter from scratch, my setup is based on x-580 frame and i also added :

* NTM 28-30s 800kv motors
* Afro esc 30A
* 10x45 props
* 3000 mah 35c 3s lipo

I am controlling the quad with a PS2 controller through X-bee modules sending ASCI characters and depending the button i press i can change the desired angles on the Quad. I am also using two arduino, one on the PS2 controller and one on the Quad. The code is made from scratch too using arduino IDE. I made 4 PIDs (one for every sensor -> acc, gyr, magn, alt). I found the desirable values of PIDs when i tied up the Quad on a rope and the Quad seems stable for ROLL and PITCH.

My problems with end up with are:

* My Quad weights 1.3 Kg, i calibrated the ESC (1000 - 2000 us) and the Quad starts to take off at 1650 us, is that normal? Isn't the value a little big to take off?

* My second and most serious problem is that when i am trying to take off the Quad flips. I first realized that i was implementing the PID while the Quad was still at ground (the ground is not always lined up) and the I term was increasing adding the previous errors, so when i was trying to take off it was too late, the error value was already big enough and the Quadcotper was fliping on one side . To fix that i am activating the PID control only above 1650us that i know that the Quad starting to take off but i still have the same results. Also when i am steering the Quadcotper to angle ex. 40 deg and i suddenly change that to 0 deg the Quad goes for example to 10 deg and slowly to Zero because the I term of the PID still has some errors in it from the previous sums (How can i deal with it?) i found a technique called "integral windup" that I term i deactivated while turning the Quad and activated only when it enter the steady state error field.

My props are installed correct, my battery is fully charged the sensors are heading in the correct direction.

Sorry for my long post, any help would be appreciated ...
mo328i is offline Find More Posts by mo328i
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 17, 2015, 09:10 AM
Team WarpSquad
United States, PA, Doylestown
Joined Jan 2014
4,149 Posts
First, with 800kv motors you probable need a higher cell count, higher Voltage. Use Ecalc to get an idea of the Voltage and Thrust required.

2- Flipping over is typically from any of the basic errors. motor and prop directions. sensor orientation, etc.

3- Very, very few of us write our own code. We use MultiWii or other code so wouldn't be able to debug what might be wrong in the code. I suggest you go and download the MultiWii open source code to study.

4- did you calibrate the Accelerometer and Gryo?
waltr is online now Find More Posts by waltr
Reply With Quote
Old Jan 17, 2015, 10:46 AM
Registered User
Joined Sep 2014
23 Posts
Quote:
Originally Posted by waltr View Post
First, with 800kv motors you probable need a higher cell count, higher Voltage. Use Ecalc to get an idea of the Voltage and Thrust required.

2- Flipping over is typically from any of the basic errors. motor and prop directions. sensor orientation, etc.

3- Very, very few of us write our own code. We use MultiWii or other code so wouldn't be able to debug what might be wrong in the code. I suggest you go and download the MultiWii open source code to study.

4- did you calibrate the Accelerometer and Gryo?
Ok about the battery, maybe higher voltage will help.

Motor and prop directions are correct i double - checked it.
I have calibrated Accelerometer and Gyro, so when the quad is straight these values are [0,0] (deg)...
mo328i is offline Find More Posts by mo328i
Reply With Quote
Old Jan 19, 2015, 06:21 PM
Registered User
United States, WA, Vancouver
Joined Jun 2013
497 Posts
PID tuning is an art, not a science. If you are rolling your own flight controller software, you are better hacker than 99.99% of the people on this board. I am a software dev with imbedded experience, and there's no way I could tackle a project like this on my own.

Go get MultiWii. All the hard, boring and error-prone stuff has been worked out for you already. Don't re-invent the wheel. It's 100% open source so you can modify til your heart's content.
SirRexAlot is offline Find More Posts by SirRexAlot
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Quadcopter flips after take off mc30900 Multirotor Talk 1 Dec 14, 2014 02:47 PM
Discussion Quadcopter Not Taking Off adambowker98 Scratchbuilt Multirotors 4 Oct 28, 2014 09:59 PM
Discussion Walkera x350 pro take off and landing problems Jrmoltz Multirotor Talk 0 Oct 26, 2014 08:06 PM
Help! Quadcopter Spins on take off allrounder Multirotor Talk 2 Oct 16, 2014 12:38 AM
Discussion quadcopter take off question? epicholymonk Scratchbuilt Multirotors 5 Sep 23, 2014 03:29 PM