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Old Oct 07, 2011, 11:44 PM
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Originally Posted by foam and tape View Post
...yaw is giving me problems. If I feed alot of yaw control in during flight it seems to hesitate, once I add more it starts to go out of control then looses control on all axis then it crashes...
If you grab the front of your airframe and the back of it and twist the nose to the right, are you able to make the front left motor go lower than the rear left motor? If you are able to twist your frame so that the front and back motors deviate from level by about an inch then differential motor tilt for yaw is the way to go.
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Old Oct 07, 2011, 11:48 PM
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yup, it all acts fine on the ground, in the air is a different story though. I'll screw around with it more tomorrow...
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Old Oct 07, 2011, 11:52 PM
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Oh, and the thing I want to attempt with the code first is to flip the mode spot on the RX and the Arduino to slowly shut off the gyro gains and hover controls to all 4 motors and letting them only respond to the throttle command, flipping the switch back on slowly brings them back to 100% gains and control. The rest of the stuff I'll let the Aurora 9 handle for now. I think its best to start off slow and just get it to "work" then tidy up the design later.
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Old Oct 07, 2011, 11:55 PM
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yup, it all acts fine on the ground, in the air is a different story though. I'll screw around with it more tomorrow...
Sounds good.

Regular quad yaw control might not work once you leave the ground since the motors will be powered up more giving them more leverage to twist the frame.

As a test you could also try putting in a couple X braces of foam into your frame to make it more resistant to twisting. Still might twist though even with bracing.
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Old Oct 08, 2011, 10:35 AM
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I've got a thought regarding yaw control - why not swap the CW and CCW propeller pairs and reverse the controls & gyro direction to compensate? That way, when you wish to yaw right for example, the rear right and front left motors speed up instead of the rear left and front right. Now any frame twist will actually work in the same direction as your desired rotation rather than fighting it.
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Old Oct 08, 2011, 11:47 AM
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Originally Posted by Rocketman1092 View Post
I've got a thought regarding yaw control - why not swap the CW and CCW propeller pairs and reverse the controls & gyro direction to compensate? That way, when you wish to yaw right for example, the rear right and front left motors speed up instead of the rear left and front right. Now any frame twist will actually work in the same direction as your desired rotation rather than fighting it.

THAT IS the most brilliant thing I've heard so far today! Before using the Ardruino board, I set up the KK board in favor of the torque/airframe twist without even realizing it, hence why yaw was actually viable. Now after setting it up I put the props on the opposite ends and the whole thing is basically working against each other in flight!!!!!

Thanks rocketman1092, I just spent all night in my head trying to diagnose why it flew like S#@!, I'll test it sometime today.
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Old Oct 08, 2011, 01:33 PM
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Great idea Rocketman1092.

If we still have weak yaw due to the large fuselage sides try tilting the front motors away from the back motors and vise versa a little.

Attached are some changes that will turn the gyros on or off as well as motor commands from the Aux1 channel. It's a hard switch until one of us comes up with a way to smooth out the transition. I'm literally soldering mine together now so I can't test anything yet. Yaw gyro correction has also been reversed.

Code:
#define YAW_DIRECTION -1



  #ifdef QUADX                                              
    if (rcData[AUX1]>1000 && rcData[AUX1]<1300)                                                                  //QTR- Hover Flight
     {	
      motor[0] = rcCommand[THROTTLE] - axisPID[ROLL] + axisPID[PITCH] - YAW_DIRECTION * axisPID[YAW]; //REAR_R
      motor[1] = rcCommand[THROTTLE] - axisPID[ROLL] - axisPID[PITCH] + YAW_DIRECTION * axisPID[YAW]; //FRONT_R
      motor[2] = rcCommand[THROTTLE] + axisPID[ROLL] + axisPID[PITCH] + YAW_DIRECTION * axisPID[YAW]; //REAR_L
      motor[3] = rcCommand[THROTTLE] + axisPID[ROLL] - axisPID[PITCH] - YAW_DIRECTION * axisPID[YAW]; //FRONT_L
     }
      if (rcData[AUX1]>1800 && rcData[AUX1]<2000)                                                                //QTR- Forward Flight                                                   
     {	 
      motor[0] = rcCommand[THROTTLE]; //REAR_R
      motor[1] = rcCommand[THROTTLE]; //FRONT_R
      motor[2] = rcCommand[THROTTLE]; //REAR_L
      motor[3] = rcCommand[THROTTLE]; //FRONT_L
     }
  #endif
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Old Oct 09, 2011, 12:40 AM
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very nice, rcvertt! does the file already have the code in the sketch?

today I got some really good flight performance in, its showing amazing stability even with the ridiculous amount of slop in the airframe.

Quad Tilt rotor: first hover testing (3 min 57 sec)
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Old Oct 09, 2011, 02:54 AM
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very nice, rcvertt! does the file already have the code in the sketch?
It's all in there. You can open it up in the Arduino IDE and go to the Edit->Find menu and search for the lines of code.

It compiles for me but I haven't tested it in the GUI or anything so let us know if it works. You probably won't notice the hard gyro and throttle control switch if your motor tilt slow enough.

You can test the code in the MultiWii GUI before you fly with it. Remove your props and after it's armed, move the pitch yaw and roll sticks to an extreme position and give some throttle. Then use your Aux switch and you should see the motor commands change accordingly in the GUI.

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Originally Posted by foam and tape View Post
today I got some really good flight performance in, its showing amazing stability even with the ridiculous amount of slop in the airframe.
Hate to say it but that looks awesome. Just a little wiggle there in the frame I see.

How much does it weigh? What are its dimensions and is it ok if I build one. That thing just looks too cool.
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Old Oct 09, 2011, 07:38 AM
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If you want to keep a good CG to evenly load all four rotors in flight and still have a stable plane in forward flight you should reduce the wing surface on the front wing and increase that on the rear wing. since the span is pretty much fixed this only leaves the wing chord to play with, though.
Looks really nice in the hover, btw. It's nice to see it doing the "harrier bow", even though it was not intentional.
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Old Oct 09, 2011, 11:22 AM
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It's all in there. You can open it up in the Arduino IDE and go to the Edit->Find menu and search for the lines of code.

It compiles for me but I haven't tested it in the GUI or anything so let us know if it works. You probably won't notice the hard gyro and throttle control switch if your motor tilt slow enough.

You can test the code in the MultiWii GUI before you fly with it. Remove your props and after it's armed, move the pitch yaw and roll sticks to an extreme position and give some throttle. Then use your Aux switch and you should see the motor commands change accordingly in the GUI.

Hate to say it but that looks awesome. Just a little wiggle there in the frame I see.

How much does it weigh? What are its dimensions and is it ok if I build one. That thing just looks too cool.
Thanks very much RCvertt I'll mess with the sketch sometime today.

the AUW is somewhere around 14-16 oz, i'll have to get the scale out later. You should have seen just how many crashes this frame has taken its hit the ground soo many times its litterally falling apart in flight! I'm just glad that the arduino does an amazing job of flying it. The finished prototype will have much more carbon in it and be made of depron and not assembled in an hour. and YES its ok to build one, this project is for everyone. I'll document and have a better write up on this project than my last VTOL if it performs well!
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Old Oct 09, 2011, 11:25 AM
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Originally Posted by Brandano View Post
If you want to keep a good CG to evenly load all four rotors in flight and still have a stable plane in forward flight you should reduce the wing surface on the front wing and increase that on the rear wing. since the span is pretty much fixed this only leaves the wing chord to play with, though.
Looks really nice in the hover, btw. It's nice to see it doing the "harrier bow", even though it was not intentional.
yup, I know I just haven't found out how much of the wing I want to remove yet. I may be testing some FF today in it so I hope to have the wing chords and lengths figured out for the final model.
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Old Oct 09, 2011, 03:10 PM
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How are you going to move your motors? Are you going to use an external servo slow device or do you want the Arduino to handle that for you.
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Old Oct 09, 2011, 03:35 PM
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to keep it simple for now i'm using a radio channel.
I uploaded the code and it works beautifully, once I flip the switch the motors are steady on perhaps the only thing that could make it better if it slowly lessened the gains/commands. if thats not possible then a 2 second delay after the switch is flipped should be good.

I went ahead and tested the airframes FF performance and I can tell you that its absolute .... it flies like a retarded walrus It always wants to crash, wingrock is a big issue and I have no rudder control. I'm probibly going to scrap this airframe and devise a more slop free one and add much bigger vert stabilizers.

is it possible to modify the code so that once I flip it to FF flight mode, I get diffrential (gyroless) steering on the RUDD channel, its essentially swapping roll for rudd. I'm not sure if this is possible or how hard may this be?
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Old Oct 09, 2011, 04:50 PM
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...perhaps the only thing that could make it better if it slowly lessened the gains/commands. if thats not possible then a 2 second delay after the switch is flipped should be good.
I think your idea of ramping the gains/commands up and down is the best solution. It'll take a little more thought to do that though so we'll start with the two second delay for now. That should at least give the motors time to tilt to 45 degrees before the hard control switch occurs.

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Originally Posted by foam and tape View Post
...is it possible to modify the code so that once I flip it to FF flight mode, I get diffrential (gyroless) steering on the RUDD channel, its essentially swapping roll for rudd. I'm not sure if this is possible or how hard may this be?
Sure. When you switch to forward flight do you want your left or right TX stick to control motor yaw.
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