SMAX default Value in Quicktune Script

ArduPilot Lua Scripting
1

Hi all,

I don’t know if this is the right category for this, but I was wondering where the 50 as a default value for the _SMAX parameters comes from in the Quicktune-Script:

Does anyone know?
Git Blame tells me that @tridge last edited the relevant line https://github.com/ArduPilot/ardupilot/blame/master/libraries/AP_Scripting/applets/VTOL-quicktune.lua#L204

2

It is used I think to enable the logging of SMAX at all. If the values are 0 then you don’t get that data, which quick tune uses in order to decide when to stop adding gains.

Edit:

It also needs to be high enough not to actually start derating the gains as oscillations begin, since that would affect the final gains that are chosen.

1 Like
3

@WARGRaph I aggre with the @Joshua_Kordani explanation.

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4

Thanks, that makes sense.
And 50 was chosen, as it is a big enough value for most copters?

5

The SMAX parameters are the running magnitude of the difference between the lowest and highest output of the respective PID controller (run through some filters).

I haven’t seen every system out there, but as long as you know what its doing, it will be clear if you need to adjust these initial maxes to make quicktune work for you.

I highly doubt you’ll need to change them, but check (or post) your logs to be sure.

Edit: And in point of fact, quicktune stops it’s work before this limit.

6

Ah! Thats what the SMAX is, it makes sense, but I’ve not read that explanation so clearly anywhere.

I will just check next time I quicktune a copter, thanks!

7

The github readme is rather complete and has advice based on your system size.