Throttle I term not zeroing at start of AUTO and GUIDED?

Looking at the dataflash logs, it appears that the I term in the speed controller does not get reset when you switch modes - it basically drifts to one extreme of IMAX or the other. This seems to either give you a slow or excessively fast initial response.

To me, it seems like switching into AUTO, GUIDED, STEERING or ACRO should reset the I term since the target speed will have changed, so any I term is no longer valid.

You can see in the plot that the I term persists through mode changes, giving it an extra kick as soon as it goes into Guided or Auto again.

You noted a ?similar? issue here, but ended up fixing it in a different way -


Just to be a “me too”: I have seen this behavior with my automated lawn mower ( If I have it in manual for a while, when I switch to auto, it takes off at a high speed. It corrects in about 2 seconds or so, so it isn’t too bad, but a little scary until I see it slow down to normal speed. I suspected it was something like what you found but I had not analyzed it.

Aha, I think there is a missing reset_I() call here in AR_AttitudeControl. feel free to PR a fix or I can have a go at it on Monday.

Re the I-term build-up to IMAX while in Auto, Guided, etc, could you post the full dataflash log? A random guess is that the cruise-speed and cruise-throttle aren’t set quite right.

Actually, I wonder if the problem is in AC_PID - line 94 -

// reset input filter to value received
if (_flags._reset_filter) {
    _flags._reset_filter = false;
    _input = input;
    _derivative = 0.0f;

Should this also reset the integrator to 0, rather than having to explicitly call “reset_I()” - surely if you’re restarting the whole PID controller, I should also go to zero.

Don’t worry about the I build up in that case - it was something I threw together quickly in SITL to illustrate my point.

calling reset_I() as part of reset_filter() seems reasonable. When I did a quick search for “reset_filter()” it’s only used in Rover and as far as I can tell it should always be followed by a reset_I(). It looks like we’re missing the reset_I() in the balance bot code (AR_AttitudeControl::get_throttle_out_from_pitch) as well.

I’d probably want to check with Leonard Hall before making that change but functionally it seems correct.

I’ve fixed this in master by calling reset-I in the speed controller… so it’s very possible that the other solution involving adding reset-I to reset_filter is a better way to go but the effect is the same and I can make this change immediately.

We could push this into an official release of Rover-3.4… we’re getting close to starting beta testing of Rover-3.5 though… anyway… if people are really keen… we could patch the official release…

Thanks, Randy. I don’t know if it is causing much trouble for other applications, but it is just a minor nuisance for me. No hurry.

I’ll try it in my local build - no need to rush to roll it in.

@mroberts Let me know if it works. I may do the same just because I can.