Why Step Response for (Roll/Pitch/Yaw) Rate is Zero?

[MuhammadBilal1]

Describe the bug

Hi, I am using PX4 (1.14.0) in my drone which is using Pixhawk 6C, but since last few days, I am getting an issue: The Step Response for (Roll/Pitch/Yaw) Rate is Zero in the flight logs (PID Analysis). I need this doing the PID Tuning of my drone.

1- Sometimes "Step Response for Roll Rate" at ZERO line 2- Sometimes "Step Response for Pitch Rate" is at ZERO line 3- Sometimes "Step Response for Yaw Rate" is at ZERO line 4- Sometimes "Step Response for Roll/Pitch Rate" is at ZERO line

Why is this happening? I am doing manual PID Tuning, flight behavior seems fine (not 100%, but not shaking or crashing), but response is zero. I am attaching some of the logs here:

To Reproduce

Performing manual tuning. Almost all of the flights are done in Position flight mode. I am using UM982 dual antenna GPS.

Expected behavior

The PID Analysis graphs should show the correct values of the PID for each rate instead of a flat line at 0.

Screenshot / Media

Flight Log

Roll & Pitch are at 0 https://review.px4.io/plot_app?plots=pid_analysis&log=60815230-a1fb-40fd-a64b-54abfcb1d143

Roll, Pitch & Yaw at 0 https://review.px4.io/plot_app?plots=pid_analysis&log=08c14c20-38ca-404e-aee4-30c531839f56

Pitch at 0 https://review.px4.io/plot_app?plots=pid_analysis&log=f804b7d3-5bf6-49cc-bef6-3473c7e4d8b4

Roll & Pitch are at 0 https://review.px4.io/plot_app?plots=pid_analysis&log=edcf0b09-5ea0-4dce-a5d5-115349aea314

Roll, Pitch & Yaw are available https://review.px4.io/plot_app?plots=pid_analysis&log=4e796e69-30c9-4199-9063-81c6259ba9f6

Software Version

PX4 (1.14.0)

Flight controller

Pixhawk 6C

Vehicle type

Multicopter

[bkueng]

Hi This is when there's not enough motion. The result is best if you fly in Stabilized/Altitude with fast and full stick changes.

From the log it looks like the MC_YAWRATE_P is a bit too high causing noise on the outputs. I would also set MC_YAWRATE_D to 0.

[MuhammadBilal1]

Hi This is when there's not enough motion. The result is best if you fly in Stabilized/Altitude with fast and full stick changes.

From the log it looks like the MC_YAWRATE_P is a bit too high causing noise on the outputs. I would also set MC_YAWRATE_D to 0.

Hi, Thank you for your response. Ok. Is this possible to do the PID Tuning by looking at the following graphs?

• Roll Angle
• Roll Angular Rate
• Pitch Angle
• Pitch Angular Rate
• Yaw Angle
• Yaw Angular Rate

A person told me that we can do it from the above graphs like seeing the difference between the Setpoint & the Estimated lines.

For Example:

• If the difference between Estimated and Setpoint is greater, then we need to increase the I value to increase the speed of response.
• If the Estimate isn't reaching the Setpoint, then we should increase the value of P.
• If the Estimate is over the Setpoint, then we should decrease the value of P for that angle.

[bkueng]

Yes you can use the graphs. Have a look at the documentation for that: https://docs.px4.io/main/en/config_mc/pid_tuning_guide_multicopter_basic.html https://docs.px4.io/main/en/config_mc/pid_tuning_guide_multicopter.html