Hello,

Bode plot analysis is indeed not an easy to explain. It's required to understand the basics of control theory. In basecam controllers, it is used to analyze several systems, comparing it's input and output like it is stated in the description. For example, to analyze signal transfer in the "Plant", its "input" is a torque generated by the motor, and output is a signal on the IMU sensor. It shows the path of the signal from the motor via mechanics to the sensor, so it is very usable in analyzing mechanical properties of a gimbal. If you analyze "Plant + Controller", it will show this signal amplified and filtered by PID controller and all filters. This information is extremally useful, but still, it's not clear how to use it to estimate the performance of the system, right?

Fortunately, right now we are working on improved version of this tool. It will be able to make some calculations and show additional information about the system that allows estimating it's robustness (stability margins) and performance in a stabilization task. Moreover, it allows to automatically find optimal PID parameters analyzing multiple responses (different positions, different payloads) at a time, that works much better the existing PID auto-tuning algorithm, that does it only for the current position and payload.

We expect to release the new version of GUI with the updated tool in January (or February, as a deadline) and prepare detailed documentation on how to use it.

Regards, Aleksey.

The output of a gyroscope sensor is measured in "rotation rate" units. The input of PID is the same (remember it is closed loop controller), so in this case units matches and we can use amplitude and phase response directly. If we analyze different system, like "Plant" - units do not match, so amplitude response has an uncertain multiplier. But we still can compare two responses, to see how changes in mechanics affect system behavior. For example, if we install 2x heavier payload, amplitude response will proportionally decrease 2x time. Also, it still shows a distribution of amplitude response over the frequencies and phase delay (that does not depend on units at all).

Each signal can be considered as a sum of harmonic signals (sinusoidal). If you send pure harmonic signal with the 10Hz frequency on input, you can expect an amplitude and phase response on the output that exactly matches with the Bode plot at 10 Hz point.

For testing, random noise is used that cover frequencies in a wide range.

Hello, alemos, a followup question...
When I log the results of bode plot I dont get the values depicted on the bode chart. More like I am getting some sort of raw data which is later used to calculate values for the chart.
Could you please explain what are those values and how to read them? There is two columns, each showing values ranging (in me case) from -1000 to 251 in the first column and from -89 to 377 in the second one. Could you please tell how values on the bode plot can be calculated out of those or at least what do those raw numbers mean.

Thanks, Aleksey!
Could you recommend any literature to obtain those skills?
And what are the units of measure of those input/output numbers? Do they represent "rotation rate"?
And if so then why didn't I observe any rotation while this test was run?