• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

*HELP* My first H-quad with Multiwii Pro

#1
Hello everybody!

I am trying to figure out what is wrong with my quadcopter. I've made the body by myself by some aluminum and plastic, and it is very solid. I am using TURNIGY Plush 25amp Speed Controllers, Turnigy D2836/9 950KV Brushless Outrunner Motors, a normal Turnigy 2200mAh battery and the red MultiWii Pro. Everything from HobbyKing. The problem is that it is like "dangling" left and right all the time, like it is overcompensating, but only with the "roll"-axle. If I take it up high and then letting it fall, it becomes stable, but when I increase the throttle again, it starts dangling again.


I am using the MegaPirate software for the MultiWii Pro, mainly because I can't get the original software to work. The problem I have with the original MultiWii software, both 2.1 and 2.2, is that I can't find any place to calibrate the endpoints of the sticks on my transmitter (I'm using the incredibly cheap "Hobby King 2.4Ghz 6Ch Tx & Rx V2 (Mode 2)" radio). So when I arm the quad, the motors starts spinning directly, so fast that it almost lifts from the ground. I don't have that problem with the MegaPirate software, because it is possible to calibrate the endpoints on the radio in Mission Planner. So if you know how to do this with the original software, I would be amazingly glad if you could tell me! :)


I use the code that Jared showed in this video:

I will give you some pictures of my quad:

IMG_9180.JPG

IMG_9190.JPG

IMG_9192.JPG

IMG_9194.JPG

IMG_9198.JPG

IMG_9200.JPG

IMG_9182.JPG

IMG_9184.JPG

IMG_9188.JPG


I hope that someone have any idea what could be wrong. Probably there is something with the software which I need to change, because it simply seems to be overcompensating. I can go out and fly it and film from the ground if you guys want to.

Patrik
 

aiidanwings

Senior Member
#2
I can't say about yours, but my wife's current quad is using a Dynamic 4channel transmitter and the trim wanders quite a bit during flight. The same quad with the FlySky stays trimmed.
 

IBeHoey

The Warranty Voider
#3
Hey TheSwedishLoller, could you post the PID values you were using in the video? From the looks of it, it seems like you have either the P value, or D value set too high which is causing the quad to oscillate.

As for setting up the endpoints, have you downloaded the T6config program used to configure the Hobby King 2.4Ghz 6Ch Tx? Here's a RCGroup thread I found of someone trying to do the same thing as yourself, set up the endpoints of their HK TX to use with Multiwii.

Basically, all you need to do is load up the T6config software, connect it to your Tx, load up the Multiwii config, and then tweak the end point settings of each channel until you get a range of 1000-2000 with 1500 being centered. Once you have that done, you can then proceed with tweaking your PID settings. :D


BTW, I dig your aluminum frame, it looks really cool. What's the AUW?
 
#4
Hi! :D
I'm glad you like my quad. It's not the prettiest, but it's durable and has lot of space! I'm not exactly sure what you mean with AUW? (Sorry, I'm a noob :p) If it is something with the dimensions and weight, I can give you them tomorrow, because it's in the middle of the night here in Sweden right now :)

The PID values I used are shown in the picture below. I think they seem pretty high, compared to the text which shows what P value it should be depending on motor size, but I have 0.1800 just because it was like the "stock setting" and I didn't want to change things if I didn't really know what it was. Do you think that I should change the P, I and D, or only one of them, or maybe two of them? And how much? What I've read on other sites I should be very slow when changing those values.

Untitled.jpg

Another question:
The transmitter I use (Hobby King 2.4Ghz 6Ch Tx & Rx V2) has 6 channels. But what I've seen, the two "extra channels" are the things you can like turn, and not the switches. The switches are only used for throttle-cut and things like that, but is it still possible for me to change the different Flight Modes on the MultiWii, even if I don't have a switch for that? Here is a picture showing what I mean. If you have watched the ArduPilot Mega 2.5 episode by FliteTest you will know what it is, if you haven't used MissionPlanner.

Untitled2.jpg

Maybe it's possible to mix a little bit in my transmitter to make one of the switches a channel instead of only the two "wheel-things". If you want to see another video I uploaded a time ago, here it is:


It's with my old motors and old ESC's, but it is the same problem as now. After I changed to the Turnigy Plush ESC's and those 950Kv Turnigy-motors, it is not as much "over-compensation" as before, for some reason, but it is still a lot.

Thank you very much for answering!
 

IBeHoey

The Warranty Voider
#5
You seem to have a good grasp on things, not sure I'd consider you a noob :D but, yes, AUW stands for All Up Weight. I've played around with the Megapirates firmware and Mission Planner a few times (I have a Crius AIOP board) but not long enough to fully understand the tuning aspect of it. Normally when you tweak the PID values, you're going to adjust them one at a time and in very small increments. Looking at your screen shot, I can tell that you have your P value set really high and I'm willing to bet that's your problem. If I were you, I'd start in the middle (set your P value to .110) and leave everything else the same. Go see how it flies, if it's still oscillating (shaking side to side) lower the value in .002 or .004 increments until the oscillating goes away. If it becomes hard to control, or keep level, raise the P value (using the same increments) until it starts to oscillate again, then back off a bit.

If you're new to multirotors, the Megapirates firmware is probably not the best to learn on, especially when it comes to tuning. If you can, you should give Multiwii another go. It's kind of stinks not being able to assign any of the switches to actual channels on your Tx but you could use the knobs to change between different flight modes in Multiwii. Using the T6config software, just assign a mix to one of the knobs and in Multiwii assign one mode to "Low" on AUX 1, and another to "high" on AUX 1. Turning the knob all the way CCW would be low, and all the way CW would be high. It's not as convenient as a switch but it'll work. I did come across an interesting mod for your Tx that involves swapping out one of the knobs for a switch and a couple 5k resistors. If your interested I'll find the link for you.
 
#6
The frame weights about 900g, and with all electronics, battery and my camera (the weight when I fly it basically) is about 1,5kg. That may seem pretty much, but I want a very solid build which wont broke in case of a basic crash :)

I'm now going to change the P value to .110 and go out and fly it. I will take a camera with me so you can see how it flies. But I wonder why it is only overcompensating in one direction? If the P-value is that high set, shouldn't it be overcompensating in all directions, and not only the roll-axle?

Anyhow, I will try to mix a little bit in the DigitalRadio-software (like T6config but with A LOT better GUI), when I've got it compensating right.

I don't really want to open my radio and mix around with it, not yet at least :D

Thank you again for your help, it means a lot to me :)
 
#7
Hi TheSwedishLoller...
The first thing you should do if you use Megapirate is to calibrate your radio in mission planner. (make sure everything on your radio is set "0" before you do that) just follow the instructions from mission planner.

Then calibrate your esc:s

20130523_205605.jpg

Next thing is to set your flight modes. Set the first 3 to Arco and the other 3 on Althold or Loiter, (you properly have a switch that only allow you to have 2 settings if you have a 6ch radio) Stabilize mode can create a strange behavior on the card if you don't set it up properly so its better starting with acro.

After you set the flight modes you have to calibrate your accelerometer so it knows when its level (you click on "terminal" and write "setup" and enter, then write "level" and enter again. The ACC starts calibrate) When thats done you click on "Flight data" and reconnect your card.

Set the "Arducopter PID:s" as you show on your picture and go to "Arducopter Config"

I Have marked the P and I you need to change, Begin with the stabilize roll and pitch on 3,5 and the I-value on 0, Then set Rate roll and pitch to 0,15 and I-value on 0. (The bigger motors you have, the lower "Rate roll and pitch P-values" you get)

Now test it out.

If it have a heavy oscillation lower the P-value on stabilize roll and pitch to 3,2 and so on until it stops, when the oscillation stops increase the I-value until it starts to oscillate again. (much more softer then the P-values hard oscillation) Try some ware between 0.0030 to 0.0150 on your quad, its really hard to say exactly you have to test it. When it starts to oscillate decrease the value until it stops.

Then do the same on "Rate roll and pitch" I-value.

You should now have a functioning quad, now its just the fine-tuning left to do.

I hope it helped.

//Sirtoby

Ps. if you are swedish you can sen me a message and i explain it in swedish instead.
 

Soundkick

Junior Member
#8
Hello TheSwedishLoller, The esc update speed under tab "Advanced Params" is 490 at default..
The Plush esc's can only go up to 435 so you must set it to 400..
 

xuzme720

Dedicated foam bender
Mentor
#9
From the video it looks like the P is too high on the roll axis, so it might be best to start with just the roll until you get it tweaked, then start fine tuning the pitch axis. I find if I change too many things at once, it can be hard to figure out what's working or not...