First Tricopter AP platform - help would be nice :)

[JamesWhom]

Hi fellas,

So I. In the process of building my first Tricopter, as you will have gathered by the tittle. I'm having a few problems and thought this forum post would be a good way to go about fixing them.

The Tricopter - Electrohub FT kit - KK2. 1.5 - FT power setup.

I used the flitetest build video to construct the Multirotor. I used David Windesål's tutorial on the KK2 board to program it.
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1) The first issue is that the tail servo does not return to it's neutral position. It tilts either way but is not at the same angle when the stick reverts to neutral. Aargh! This won't do for yaw control! Maybe it's a Kk2 programming issue to do with the giros?

2) The second issue is that one of the motors (the front left) gitters and does not run as fast as the other motors. I partially fixed this by testing the motor unmounted to the frame to discover it ran fine. When attached back onto it, it just stutters and doesn't run properly, staying at a low speed whilst the other motors rev up. How can the frame be affecting this??

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If you have knowlage of the Kk2 board, motor troubles on multi rotors, or anything that may help, please comment and help me!

Thanks - James.

 

[LitterBug]

Hi fellas,

2) The second issue is that one of the motors (the front left) gitters and does not run as fast as the other motors. I partially fixed this by testing the motor unmounted to the frame to discover it ran fine. When attached back onto it, it just stutters and doesn't run properly, staying at a low speed whilst the other motors rev up. How can the frame be affecting this??

Sounds like there is interference between the motor shaft that sticks out of the bottom of the motor and the motor mount or your mounting screws are too long and hitting the electrical coils inside the motor. If it spins freely by hand, then it is more likely an issue with the screws.

Cheers!
LitterBug

 

[JamesWhom]

Many thanks for your quick response! I have just had a look and it appears I have used the wrong screws and they are in fact touching the coils. Brilliant, love it when it all makes sense.

Thanks again.

 

[JamesWhom]

I checked and it worked. Yippee!

 

[JamesWhom]

I have discovered that the tail servo not returning to its default position in the centre is a programming issue. So in this case the KK2 most have something that is making it not come back into the middle. As I mentioned before, it could be a gyro issue.

Any ideas?

 

[makattack]

Afraid I've no experience with the KK2, but I do know that the default firmware shipped from HK is known to be buggy and features poor flight characteristics. I don't suppose you've already reflashed it with newer firmware? I believe there are two to choose from, with one being from steveis (who is the main man behind David Windestal/RCExplorers triflight software derived from cleanflight):

http://www.rcgroups.com/forums/showthread.php?t=2060802

 

[JamesWhom]

Hi Makattack, thanks for your help. I haven't actually bothered to update the firmware. I decided that I would do so at another time. I'm guessing this may be the problem then if it has such a reputation.

The initial reason behind me not upgrading the firmware is that I did not get a cable that I could connect the board to my computer. Maybe I should get round to ordering one in light of this.

I have had a further issue that maybe someone could help me with:
3) whilst attempting to rectify an issue with the KK2 reciever test settings, the parameters of movement are only between approximately -30 and +30 on the rudder channel. This means that now the copter will not arm. I have read that you need to have the parameter meeting +50 Right so when moving the stick left, it will arm the copter. Obviously I need to increase these numbers by changing the 'endpoint adjustment'. However, I am using a DX6i, and there is, as far as I am aware, no way to do this! So, what do I do now to make it -100 and +100?

Cheers.

 

[makattack]

Ah, at least I can help with the DX6i stuff... If you need to adjust your yaw/rudder travel adjustment, go to the TRAVEL ADJ screen and modify the RUDD values for both left and right yaw (you'll need to move the rudder stick in each direction to change that directions travel end point)

 

[JamesWhom]

Thanks again for your help. I have done as you said and increased the percentages to 125%, yet the kk2 is saying that the travel is still only +40 max. It has increased the end point, but not enough.

 

[makattack]

Sorry JamesWhom, I'm not sure why that is. You're not setup for low rates or expo on the DX6i are you? Though that seems too obvious, it's sometimes the obvious/easily overlooked that makes for the most vexing of problems to solve.

 

[paulshort]

the tail servo is moving correctly. It will not center until the craft has turned to where its supposed to be. Put some props on and you will see what I mean. This is how it is on my flight controllers I have used. (I may be wrong)

 

[JamesWhom]

Sorry JamesWhom, I'm not sure why that is. You're not setup for low rates or expo on the DX6i are you? Though that seems too obvious, it's sometimes the obvious/easily overlooked that makes for the most vexing of problems to solve.

I have checked and this isn't the case unfortunately. I know what you mean though! When building other aircraft, I often look over the simple things.

 

[JamesWhom]

the tail servo is moving correctly. It will not center until the craft has turned to where its supposed to be. Put some props on and you will see what I mean. This is how it is on my flight controllers I have used. (I may be wrong)

Hi, I will have a try. The thing is, I did put props on it a few days ago and it span round erratically. Never the less, I will have another go now I have fixed a few other problems with it. (That is if I can get the thing to arm, I still need to fix that problem with the reduced resolution of the receiver test results).

 

[LitterBug]

Hi, I will have a try. The thing is, I did put props on it a few days ago and it span round erratically. Never the less, I will have another go now I have fixed a few other problems with it. (That is if I can get the thing to arm, I still need to fix that problem with the reduced resolution of the receiver test results).

When I had a DX6i, I went into the travel adjust and set all the channels to +-125%. That set the travel ranges closer to 1000-2000 for better resolution. If you don't do that, it will be more like 1120-1880. You have to set the top and bottom endpoits seperately. When you are in the range adjust mode, there is an arrow that indicates which direction you are adjusting. To adjust the bottom of the throttle channel, move the throttle stick in the down direction. Move it up, and the arrow flips the other way to adjust the top range.

Cheers!
LitterBug

 

[JamesWhom]

I have checked and this isn't the case unfortunately. I know what you mean though! When building other aircraft, I often look over the simple things.

You're right it does correct itself when the copter has props on and throttled up. That really helped my confusion, so thanks a lot.

 

[JamesWhom]

When I had a DX6i, I went into the travel adjust and set all the channels to +-125%. That set the travel ranges closer to 1000-2000 for better resolution. If you don't do that, it will be more like 1120-1880. You have to set the top and bottom endpoits seperately. When you are in the range adjust mode, there is an arrow that indicates which direction you are adjusting. To adjust the bottom of the throttle channel, move the throttle stick in the down direction. Move it up, and the arrow flips the other way to adjust the top range.

Cheers!
LitterBug

I managed to work it out earlier that this was the problem! Was just about to post about it in this forum thread when I saw that you had suggested the same thing. I set all of the adjusts at -+ 125, and checked expos were all at 100. The resulting numbers that I had been looking for on the KK2 receiver test were satisfying to see appear.

Okay, so nearly there now, but there is another problem that I need to overcome.

4) During trial throttle ups outside to try and lift off, the copter runs up the motors and everything looks okay at first, but when it lifts, it yaws around madly. I have also noticed that some of the motors actually throttle up more than the others. I have also noticed that when I push the joystick over to one side for a few seconds without any throttle imput, one of the motors will start throttling up very slowly; When I increase the throttle from this point, this motor will throttle up and be far faster than the others, flipping the copter over. Is this the result of some mode on the KK2 board? I don't get it! It's like it's overcompensating.

All of the motor rotations and props are correct.

Cheers

 

[LitterBug]

Sounds like the servo direction may be backwards... No experience with KK2 or how to check that with your setup.

Cheers,
LitterBug

 

[JamesWhom]

Sounds like the servo direction may be backwards... No experience with KK2 or how to check that with your setup.

Cheers,
LitterBug

Hi, unfortunately that isn't it.

And
Home with KK2 experience out there? David Windesål help me please

 

[makattack]

Fewer people are using the kk2 board these days, buy that doesn't mean they aren't around. They just might not have much more advice other than to make sure you are not on the stock firmware that seems to solve a lot of problems.

David W/rcexplorer has a great kk2 set video you should check out where he recommends the same.

Still, what you describe could happen on any flight board and usually is a miss configuration.

Double check the esc/motor signal lines going into the kk2. Double check board orientation. Did you successfully calibrate your esc's?

You say your tail servo setting on the kk2 is correct, but did you test it? With no props on, if you run up the motors and give left yaw, the top of the trail motor should point to the right, following your command. Next, center the tail with the stick and with the motors running, pick up the tricopter and manually yaw it left and right with the sticks all in the middle/centered. Now, the motor should do the opposite. Left yaw, top of motor points left to OPPOSE the uncommanded yaw. Right yaw, motor top points right.

 

[JamesWhom]

Fewer people are using the kk2 board these days, buy that doesn't mean they aren't around. They just might not have much more advice other than to make sure you are not on the stock firmware that seems to solve a lot of problems.

David W/rcexplorer has a great kk2 set video you should check out where he recommends the same.

Still, what you describe could happen on any flight board and usually is a miss configuration.

Double check the esc/motor signal lines going into the kk2. Double check board orientation. Did you successfully calibrate your esc's?

You say your tail servo setting on the kk2 is correct, but did you test it? With no props on, if you run up the motors and give left yaw, the top of the trail motor should point to the right, following your command. Next, center the tail with the stick and with the motors running, pick up the tricopter and manually yaw it left and right with the sticks all in the middle/centered. Now, the motor should do the opposite. Left yaw, top of motor points left to OPPOSE the uncommanded yaw. Right yaw, motor top points right.

It works!

Thank you so much for your help. I had completely misunderstood the logic of the tail servo, as you somewhat predicted. Thank you for your explination of which way it should be pointing to get the thrust to turn the Copter. I did have some thoughts that it may be the wrong way arround as the machine seemed to think it needed to turn into the way it already was turning, worsening the spinning motion.

Solution

In light of this realisation, I went into the 'mixer editor' and switched the channel to channel '4'. From this I changed the '100' value of the rudder to '-100'. This reversed the motion of the rudder so that it now reacts in the correct way to stick input and gyro stabilisation, as described in the quote above.

Testing

So I took it outside and tested the copter to see if it would take off property this time and it did! It hesitantly lifted off of the floor and stayed in the correct orientation.

Problem solving, however tedious and frustrating whilst attempting to rectify the problem, is so satisfying when you overcome the obstacle and achieve what you have been wanting that whole time. I imagine that this is another element of the hobby that makes it enjoyable.

The next thing to do is to fine tune things, and of course update the firmware on the board, and look for any other problems that might pop up before I proceed with building some nice wooden landing gear legs and a camera rig. fun fun.

Thank you again for all of your help. Will keep updating this thread, inc. photographs, of my progress with this Electrohub Tricopter project.