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Re: Axis Hold / Rate stabilization
« Reply #15 on: December 28, 2017, 05:59:53 am »
Well, I thought the gimbal stabilization was working - but it seems to be erratic. I have two identical systems on separate parts of the aircraft, and they can move independently. Sometimes it powers up and works. More often not. Sometimes one side (one side much more than the other) sometimes the other - its hard to get them BOTH running at the same time. On a fixed bench more often than not they both work - but in the field its another matter - I can rarely get them to both work. I can't seem to find any reason why. Sometimes they start working after a period of time. But most annoying is even when both working, after some time, for reasons unknown, one or the other stops working. I can move the control inputs, and it will move the servos - that part always works - but the tracking just stops responding. It's like there is some condition(s) necessary for it to work, and if those conditions aren't met, it doesn't work. But what are they?
One of the sides also has a weird tendency to loose the board rotation parameter. Then if I unplug and replug, it will come back correctly.

There is a 3rd FC on the main body of the aircraft, running differential on the motors. That seems to be working fine. Im still tuning the PID, but it seems to power up and down reliably.

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Re: Axis Hold / Rate stabilization
« Reply #16 on: December 28, 2017, 09:28:39 am »
The gimbal is supposed to only use the current bank angle and not the RC input at all.

Imagine how a gimbal is supposed to work.  It should simply be the opposite of the bank angle so that the camera mounted on it is level.

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Re: Axis Hold / Rate stabilization
« Reply #17 on: December 28, 2017, 08:22:56 pm »
Perhaps I wasn't clear. My use of the gimbal is exactly like its use with a camera. I want the "camera" to hold a certain position relative to the horizon. I move a joystick to change that angle - then I expect the gimbal system to send a signal to the servo to move the camera until it gets to that position. If the system moves, it will keep tracking sending a servo signal to move the camera until it gets to my desired position. The change of position happens by incremental movements of the control inputs. A short pulse moves the angle by some delta.
This all works - sometimes. I can use the control inputs to move the camera position - that always works. What doesn't always work is the feedback from the FC to the servo to change position when the FC shifts attitude. Sometimes it does - sometimes it doesn't - and I can't figure out why.
I'm using channel 1, assigned to Accessory 1. 180 degrees input range & speed, roll only, Axislock stabilization mode. pitch & yaw inputs are set to none.
I have limited signals to/from the FC, so I just replicated channel 1 on all the other inputs - throttle, roll, pitch, yaw. It seems to need something on these channels or won't run at all. I have one other input I've been using for mode control on a switch - at some point I'd like to get more control over this function at least with a switch to change modes. But right now it's not doing anything.
Are there some arming conditions that need to be met? I have Always Armed set.

Re: Axis Hold / Rate stabilization
« Reply #18 on: December 28, 2017, 10:19:33 pm »
It's been a while with gimbal for me, but even for Always Armed it must wait for the gyros to init and the default waits for the FC to be PERFECTLY motionless before doing gyro init (calibration).  You generally must leave it setting on a firm surface for gyro init to start.  It does "fast blink" during init.

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Re: Axis Hold / Rate stabilization
« Reply #19 on: December 31, 2017, 07:41:03 pm »
Thanks! Yes, that seems to be the issue - one of the FCs takes a long time to init - the way the machine is built its not easy to hold it perfectly still, but applying some props to hold it - eventually it does init, then everything works as expected.
Are there any conditions that would make it stop responding?

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Re: Axis Hold / Rate stabilization
« Reply #20 on: December 31, 2017, 08:19:59 pm »
I also found a workaround for the gain on the gimbal mode. I use 180 degrees for input, but output is 45 degrees. In/out = gain.
Now if only I could change these values in the field with Librepilot2go...