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Permalink Reply by Glenn M on April 23, 2012 at 6:26pm

I should add, the servo is a BMS-358DMax on a 5v bec. Its movement is quite jerky. I've tried it on 6v, but it just made it jerkier.

The servo also sounds like it buzzes for a while even when I've stopped the motors.

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Permalink Reply by Glenn M on April 23, 2012 at 9:32pm

Alright I've somewhat sorted it. I moved the linkage to the other side of the arm, which didn't change anything but it made it the same as the build guide pics.

Here's what happened with a few tests.

with 2.5.4 firmware stock
yaw not reversed in radio setup

tri will spin around to south east and oscillate back and forth about 45 degrees
stick inputs are reversed.

yaw reversed in radio setup
tri will hold its heading and correctly fight changes to the yaw made by hand. 
stick inputs are reversed, but yaw returns to centre with no stick input.

2.5.4 firmware with Randy's AP_motorstri.cpp change - Link
yaw not reversed in radio setup

tri will spin around to a heading and oscillate around it.
control inputs are reversed, yaw don't return to centre after stick input

yaw reversed in radio setup
tri will spin around to a heading and oscillate around it.
Control inputs are correct, but yaw doesn't return to centre after stick input

So I've gone to 2.5.4 stock without Randy's change in AP_motorstri.cpp, and just reversed my yaw stick input on my transmitter, and now it's holding its heading correctly, and stick inputs move it in the correct direction.

However it is still only using a small amount of the servo's travel, and not really yawing very fast as a result. Can this be changed at all?

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DeveloperPermalink Reply by Randy on April 25, 2012 at 6:20am

Glenn,

    In general, I don't think you should need to reverse your radio's yaw channel but to be sure what you've done is correct, compare the mission planner radio set-up screen's yaw channel moves in the same direction as your sticks.  I don't think you should ever click the little "reverse" checkbox that appears beside the green and grey slider.

     Re the small servo travel, I think you just need to increase your stabilize yaw P value.  This can be found in the mission planner, Configuration, OLD ArduCopter Configuration.  You'll see a stabilize Yaw P,I and D values on the upper right side of the screen.

     I think the fix I provided for the yaw servo reversing may be doing what it's suppose to but you've got some other problems that are masking it.  That's my hope anyway!

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Permalink Reply by Glenn M on April 25, 2012 at 7:53pm

Yeah I am a little stumped by this. If I don't have the yaw 'reverse' box checked there, then the automatic stabilising yaw movement works in the wrong direction. I've just checked my radio setup, and with the yaw reverse box checked and also my TX yaw output reversed, the green bar moves in the same direction as my sticks.

Logically I thought that I should be able to leave the yaw reverse box unchecked in radio setup, and not have my yaw stick on my TX reversed, but doing this causes the auto yaw to stabilise in the wrong direction, and then oscillate around a heading as above.

I can create logs showing each case if it would help understand what is going on, but I'm just going to use it as is for now.

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DeveloperPermalink Reply by Randy on April 25, 2012 at 9:00pm

Glen,

     Ok, no, it's my mistake actually.  In the patch I'm checking the yaw channel to see if it's reversed or not...but I should be checking channel 7.  Don Cramer makes this clear in issue #228 so this is 100% my mistake!  I'll fix it up, hopefully tonight.

-Randy

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Permalink Reply by Glenn M on April 27, 2012 at 4:25am

Alright thanks, so I should try your new fix, and un-reverse everything then?

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ModeratorPermalink Reply by Dean Wynton on May 3, 2012 at 6:50am

Hi Glenn,

I have the reverse channel box checked and reversed the channel on my radio also. I think if you reverse the channel on your radio you must check the box? either way it works for me..

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Permalink Reply by Ryan McCon on May 21, 2012 at 7:40am

I have this setup working on my tricopter, same one, the delrin kit from fpvmanuals. One thing I have noticed is that you need to set it up with the motor tilted a good 10 degrees to the right I think. I first set mine up with the tilt motor being perfectly level and realized a needed a bunch of sub-trim on the transmitter to get it to fly without yawing. Or more accurately in order to have a similar amount of yaw authority in each direction. The ardupilot board was able to stop the yaw (once I got all my servo directions and reversing in programming right) but I noticed a couple things. Mainly when I input yaw the tricopter would respond appropriately, but when I stopped it would bob back and forth a bit before stabilizing. I believe the servo was going back to neutral position, which would then cause it to yaw, and the ardupilot would then move the servo as needed to stop it.  Here is what fixed it mostly for me. Turn stabilize mode off. Use rate mode and lift off. Warning - it will be VERY hard to control if you are used to stabilize mode. But turn your dual rate adjustments down and get it so that you can control it. Notice how much it yaws, and in which direction. Use sub-trim on the rudder channel in order to get that to stop so that it won't require stick input to stop it from yawing. 

Land and note the position of the motor. Clear out the subtrim and mechanically adjust the pushrod length to get the motor in that position. Take off again. when you have the yaw pretty much stopped in rate mode, and with no subtrim on the radio you should be all set. Now you should have a much smoother flying tricopter with similar amounts of yaw authority in each direction. 

Don't worry about how much the servo moves so much. I worried at first, but once making those adjustments I have found I don't need more servo travel. 

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Permalink Reply by Ryan McCon on May 21, 2012 at 8:36am

I've flown mine with props spinning both directions as depicted above. Made zero difference to the handling of the quad. Possibly some difference in vibrations, but flew the same. 

I initially had a hard time with the direction of the servo yaw as setup in mission planner vs servo yaw direction on my transmitter in the servo reverse setting there. 

Try turning rate mode on and lifting off that way. Make sure your rudder stick makes the servo move the right way. You can actually do that on the ground I suppose, before the motors are even armed rate mode will work the rudder servo. 

Then once you know that one is right, take off in stabilize mode and see if it spins. If so, chances are that mission planner needs to have it's reverse set for yaw. 

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Permalink Reply by Ryan McCon on May 21, 2012 at 8:52am

do you have any expo configured in your tx? That could smooth out the sensitivity on yaw. 

I've got 17" booms on mine, and the yaw isn't sensitive at all. It's fairly smooth and gentle. 

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DeveloperPermalink Reply by Randy on May 23, 2012 at 7:17am

We could add a trim value to the tail servo as well to allow you to set the neutral position...maybe we should do that..

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Permalink Reply by Luke on May 23, 2012 at 10:27am

Yes please, this would be fantastic.

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