# Z Rate Behavior

**URL:** <https://discuss.px4.io/t/z-rate-behavior/7009>\
**Category:** PX4 Autopilot\
**Created:** [June 27, 2018, 4:53am UTC](https://discuss.px4.io/t/z-rate-behavior/7009 "2018-06-27T04:53:32Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![dejamzo](https://discuss.px4.io/letter_avatar_proxy/v4/letter/d/977dab/32.png) [@dejamzo](https://discuss.px4.io/u/dejamzo)\
**Post date:** [June 27, 2018, 4:53am UTC](https://discuss.px4.io/t/z-rate-behavior/7009/1 "2018-06-27T04:53:32Z")

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Hi all, I am in the process of tuning the velocity controllers (already tuned angular + ang rate). I noticed some unusual steady state behavior while doing the Z rate where it seems to settle at a different value to the setpoint. I’ve also noticed this previously in high level position control.

Here is the log [Flight Review](https://logs.px4.io/plot_app?log=7a4718b9-e6db-47a3-b447-d5e5512dbbe0)  
Since the online plotter doesn’t show velocity setpoint, the step inputs given are +/- 0.5 m/s (which is equal to the full stick max velocity)

Note that I’ve purposely increased MPC\_Z\_VEL\_P to induce some oscillation so it is clear where the system eventually settles.

Motion capture is being used if that is significant, although the mocap and estimator positions appeared almost identical.

Is there some other saturation which would explain this behavior?

Cheers