Replies to This Discussion

DeveloperPermalink Reply by R_Lefebvre on March 16, 2012 at 1:57pm

Guys, when you route the Gyro signal through the APM, it does not pass straight through.  It goes through the heading control system first.

I don't have any experience setting it up with an external gyro.  Hopefully Randy or Malcolm can chime in.

I believe that one of your problems might be the Stabilize Yaw PIDS.  Set I and D to zero, and then work with P to try and remove the oscillation.  It might be that your gyro needs to be in rate mode instead of heading-lock mode.

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Permalink Reply by Christoph on March 16, 2012 at 3:44pm

That makes sense. My ext. gyro is in heading hold mode, so then there were two cooks in the kitchen.

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Permalink Reply by malcolm churn on March 16, 2012 at 3:50pm

I run my external gyro in HH mode and it is rock solid, i need to increase the P setting to get a faster deg/sec turn rate but for me it works well...

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Permalink Reply by Ravi on March 16, 2012 at 7:52pm

hi malcolm, i am yet to test fly my align450 in stabilize mode. everything seems to be set up properly. should i use the internal yaw gyro of APM or external yaw gyro of futaba by enabling the external gyro in mission planner setup. also my tail rotor moves less than 1mm when i move the yaw stick of Tx in stabilize mode. i think the yaw movement of tail rotor should be more. i am just trying to be careful for my first flight.

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Permalink Reply by malcolm churn on March 17, 2012 at 6:11am

You will need more than 1 mm of tail movement! , i use an external gyro because i like flying with it, but the guys are having good results using the APM as the tail gyro. If you have an external gyro mounted on the heli, then try it, if not then tune the APM, play with the PID on the Yaw settings, do this for both external and internal. But you really need to raise the movement. Have you gone through the M setting in the CLI? 

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DeveloperPermalink Reply by R_Lefebvre on March 17, 2012 at 4:58am

Huh, that surprises me that it works as I would expect it would be "too many cooks in the kitchen".  Two circuits trying to, not just stop rotation, but actually hold a compass heading.

My only guess then would be that the external gyro is so good, that the APM isn't seeing any compass movement at all, and/or, if it sees a little movement and outputs some control response, those signals are so small that the ext. gyro is just interpreting them as noise.

Anyway, any help you can give these guys is appreciated Malcolm as I just haven't used that system.

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Permalink Reply by malcolm churn on March 17, 2012 at 11:22am

ok when i run an external gyro the internal one is turned off, (or thats what i think) the heli flies just like does if it only had an external one. The difference comes when you are flying an RTL or in AUTO on a set of waypoints. The apm then tells the heli which i direction it should flying, so all the software needs to do is turn the heli to the desired heading (much like you would by moving the rudder control) the external gyro takes care of all the torque rections. Once its on that heading the apm can make small adjustments to keep it true)

My settings are as follows.

Stab Yaw.

P- 7.000  I- 0.010 Imax- 8.0

Rate yaw

P- 0.130  I- 0.000 D- 0.000 Imax- 10.0

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Permalink Reply by Christoph on March 16, 2012 at 1:58pm

Yusong, before trying to fly I recommend to test as much as possible on the bench. Check in stab mode if the swash is moving in the right direction. Let the heli sit levelled on the bench and just wait. If the swash starts slowing leaning to one side, then your I term might be too high. This could lead to a strong leaning effect when you want to take off. I disabled the I term for stab totally.

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DeveloperPermalink Reply by R_Lefebvre on March 17, 2012 at 7:03am

Just a quick note on those Mi servos that I bought from Hobby King.  I'm not quite sure what to make of them.  On the face of it they seem like good value, they look to be well made with titanium gears for a nice price/performance.  However I'm not convinced of their reliability.

I had one fail very early on.  I ran all of them on a servo tester for 30 minutes without problem, but then one of them died while I was setting up the heli.  I'm not sure if it just died, or if I plugged a servo lead in the wrong way.  Obviously that's a mistake, but every servo I've ever used has been capable of withstanding this.

Then I made the mistake of plugging 3S direct into them.  One of them immediately let the smoke out.  Obviously this is my fault.  However I find it interesting that the 2 remaining ones are fine.  There seems to be great variability in their built in that regard.

Finally, the HK470902 that I have, the fastest one, seems to exhibit a really bad flutter around center.  It's similar to the way normal digital servos can flutter a bit if you plug a freshly charged 5-cell NiMh battery.  I think the internal PID loop is being overdriven with the high voltage.  So, it's just like that.  It appears to go away if I run it with a 6V regulator.  And it only happens right around center.  If I move it to a position off-center, it doesn't happen.  Weird.  The arm doesn't really move, but you can hear the thing basically banging back and forth at super high speed.  A buzz.  I only have one of these, so I don't know if it's indicative of a design problem, or a one-off quality issue.

I'll continue to experiment with them, but at this point I can't recommend their use on a really expensive machine.  Of course, I'm sure people with $1000+ machines wouldn't be interested in these $35 servos anyway. ;)

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Permalink Reply by malcolm churn on March 17, 2012 at 11:27am

I'll continue to experiment with them, but at this point I can't recommend their use on a really expensive machine.  Of course, I'm sure people with $1000+ machines wouldn't be interested in these $35 servos anyway. ;)

I stay away from those servos, in my mind if a servo fails then in a heli it will crash as we all know. There are way too many things that can go wrong and at least by using futaba servos i have some peace of mind. 

One thing i would say, as we are not flying 3d but mostly hovering, then there are some good Hitec serovs which are a lot cheaper that are worth looking at, if anyone is interested i'll do some homework and go through some reasonably priced ones.

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Permalink Reply by Christoph on March 17, 2012 at 1:51pm

I might have found a bug in 2.4.

When in loiter or position mode, a manual stick input in pitch or roll, which usually resets the loiter position, disables a correct function of loiter mode. Nav goes all of a sudden down to zero. The funny thing is, even switching out of loiter and back to loiter mode, does not help. Loiter becomes unusable until you reboot the APM.

I think other pilots might have had the same issue, because I read in some posts, that after some nice loitering, all of a sudden the quad drifts off to one direction and never comes back. Same happened to me. Reason, because I touched the roll/pitch stick and freaked up the loiter function by doing that.

Is it a known issue?

Does manual stick input not reset anymore the position?See, when I put in a roll signal, the nav values go back to zero, but the long and lat error freeze.

Btw, when the long and lat error go down to zero, that is when I switch out of loiter. After that I switch back, but no effect anymore. Loiter seems to be not working then anymore.

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Permalink Reply by malcolm churn on March 17, 2012 at 2:46pm

you may well be correct, the first time i hit loiter the heli did its usual circles, i switched out, got it stable again, hit loiter and it just held its heading. 

Anyone else agree?

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