Desired pitch versus Normalised pitch

ArduCopter Traditional Helicopter
1

I graphed the pitch values of a 450 size flybar, with arducopter V4.0.5.

PDes versus POut__Heli__flybar
PDes versus POut__Heli__flybar1366×768 521 KB

PDes versus P__Heli__flybar
PDes versus P__Heli__flybar1366×768 520 KB

The P Des versus P coincides very well, while P Des versus P Out offset by a lot.

See attached.

While I understand P Out is the actual output to the servo, what is P (Normalised pitch value) ?

And is it normal for such an offset ?

Thanks.

2

Correction :–

I made a mistake in the last post, and mixed up P and P Out.
P is pitch rate, and P Out is normalised pitch output.

In my case, desired pitch (P Des) coincides with normalised pitch (P Out) very well,
but offset from P (Pitch rate) by a lot. Should I care about it ?

3

Yes Rate.P is pitch rate in rad/s. Rate.Pout is the output to the motors mixer. I may or may not match desired pitch rate (Rate.Pdes). Since for heli’s, VFF is used primarily, then they look very similar.

You should care about how well Rate.P matches Rate.Pdes. Ultimately, you really want ATT.Pitch to match ATT.DesPitch well. Now in both cases, you may see some time delay but the actual pitch should follow the desired pitch quite closely.

4

Thank you for your reply. I searched the web and know roughly what is the meaning of normalised value in graphing.