Tuning question

Hi all!

I have a question to all experienced users out there!

I’ve heard that the acceleration parameters under the angle P in the extended tuning page is only there to adjust the feeling of flying the aircraft.

Is this really what it is? My experience is that when I have a bad PID tune, I can hide it by lowering the accel values. But if I increase them I’ll have to lower my PID values a bit. So, from that, a well tuned aircraft should be able to handle much higher accel values right?


Unscientific = I’m not a real expert. I try to understand the parameters, and I’m happy to help with tuning where I can.

ATC_ACCEL_x_MAX parameters limit the maximum acceleration in each axis to something that’s achievable given the responsiveness of the drive system (props/motors/ESCs/battery C) and the inertia of the copter.

The ideal values can be obtained via Autotune, or maybe extensive manual tuning and log examination. Always start with the calculated values from the tuning guide or Initial Parameters calculator in MissionPlanner.

You can lower the Accels to “soften” the attitude control, but I would only do that to a very limited degree and there are other dedicated parameters related to the “feel” and pilot input.
If you set the Accels too low, even if adding a payload, the copter becomes susceptible to disturbances and will be unable to react appropriately. Even the basic attitude control can suffer.

new ATC_ACCEL_x_MAX = ATC_ACCEL_x_MAX * (min_TOW / max_TOW)
(TOW = take off weight)

The ATC_ACCEL_x_MAX parameters should be adjusted down from ideal to allow for a payload.
With a payload your copter has more inertia, so you dont want to stress the drive system by attempting unachievable accelerations. If there’s a camera gimbal you may want to keep Accels within the limits of the gimbal capabilities.

With a small copter, where adding a camera might be almost doubling the total weight, I would limit the reduction of the Accels to 66% of original. If you go too low the attitude control suffers. I dont have an exact value for that cutoff, but it’s easy to tell when you’ve gone too far :slight_smile:

ATC_ACCEL_x_MAX values can be rounded to nearest hundreds or thousands and less significant digits and decimal places are not critical.

I would make a slight adjustment to what @xfacta said.

Autotune will generate the maximum values for a given aircraft and tune. You can then reduce these to achieve the pilot feel you want.

This is not strictly true. We use this for two purposes. We use it to adjust the feel of the aircraft response to pilot input and also limit the aggressiveness of the attitude corrections from large angular disturbances. This is important on large aircraft where the aircraft lacks the power to stop rotation quickly. If these aircraft have large ATC_ACCEL_x_MAX settings the aircraft can fly perfectly until it experiences a large disturbance. Past a certain angle the aircraft picks up too much speed to stop again and overshoots. This parameter limits this maximum speed to prevent this.

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