I have a bixler with APM 2.0. Recently I updated the firmware to 2.50 but now the behaviour is weird. When I turn stabilization on it goes really smooth, actually I think better than 2.40 . However, when I touch the stick the counter action is not as smooth as it used to be, for example if I pitch up to gain altitude when I release the stick it dives very hard, with a sharp movement. Landing was a piece of cake and now it has become really hard, and I even crash today due to this hard/sharp counter actions to my stick movements done by the stabilization mode.
Another strange thing is that when I set RTL the plane again the plane reacts really sharp.
I use bixler.param file as I used to do it with the previous 2.40 firmware without problems.
On the 2.50 release notes it says something about some two parameters I need to change ...is it my case??
Any help appreciatted, if I don't find a solution soon I am forced to downgrade to 2.40 again :(
Check your PID settings. There were changes in the "interpretation" of their values, meaning in order to get the same or similar behaviour back you need to actually scale some of them. There is more detailed information in the 2.5 release discussions.
problem is it says
This has been fixed by making the PID library calculate the delta time internally, but it means that existing HDG2RLL_I and HDG2RLL_D values will be incorrect. I have fixed the defaults, but if you have your own settings for these, you will need to drop HDG2RLL_I by a factor of 5, and raise HDG2RLL_D by a factor of 5 to get the same result as for the previous release.
So do I need to substract and add, or divide and multiple this values respectively by 5 to the current bixler param file values?
Would be great if there was better documentation about this available. I haven't looked at the code changes (not to mention I'm not a developer :) and haven't tried myself the new code. So do this on your own risk:
Based on my understanding, the change in navigation control is now computed more frequently than previously (that's a multiplicative factor), which means that HDG2RLL_I (which is the "integrative" term) should be divided by 5, while HDG2RLL_D (which is the "derivative" term) should be multiplied by 5. That's the only change that makes sense to me. Maybe someone else can confirm this. I plan to look at the code before actually flying it myself but I have other problems at the moment.
The PID settings for stabilisation (in stabilise and FBW modes) didn't change, so the change in response to stick input is not expected. Do you have tlogs of flying with the previous version versus the current version that I could look at?
unfortunately I don't, because there is something weird going on with dataflash as well, ( same problem as guys from mygeekshowdotcom ).
As I said, seems to work really well, although when I enter inputs, specially pitch stick, the behavious from the plane is to counter react sharply to my movements ( lets say, if I pitch up then it responds with a sharp pitch down ).
I uploaded 2.50 with default parameter settings? Before I fly with it..do you thing it is going to work? The only thing that surprise me is the hard response of the rudder in stabilization mode compared to the smooth one with bixler.param.
Anyway, if it doesn't work and if there is not any other suggestion from you guys I'll probably go for bixler.param, knowing that issue I have with stabilization.