Hello, I am a user who is trying px4 auto-flight using the 3w 275 engine.
However, automatic flight failed due to engine vibration, and after looking for a method, I found out that rpm Based Dynamic Notch Setup.
Can anyone tell me step by step how to apply it? thank you
What is PX4 Auto Flight?
pixhawk4 cuav v5+ with ardupilot
Sure, here are the instructions: Managing Gyro Noise with the Dynamic Harmonic Notch Filters — Copter documentation
Make sure you activate ESC telemetry and that the NR_POLES parameter is set to the correct value.
thank you relply.
but where is NR_POLES parameter? and my engine is gas engine , I need to set activate ESC telemetry??? or RPM sensor ??
Looks like it’s probably a combustion engine. So set up an RPM sensor and set notch mode 2. It’s all in the linked instructions in explicit detail.
Ignore the ESC and poles parameters. They do not apply to a combustion engine configuration.
Thank you for your response.
I have a few more questions.
2.after analyzing the hover throttle, is there a parameter to apply separately for frequency?
Use ArduPilot Filter Review Tool it will do the gyro0 FFT for you.
The parameters are all on that tool
This notch filtering also applies to regular planes, correct?
so, about the rpm sensor and IC engines…
does the notch filter assume that engine only fires once per revolution (ie: single cylinder or boxer)?
what if i have a 5 cylinder engine (2.5 firings per revolution)?
would that not work with the rpm notch? i’m guessing i’ll need to use a different method?
What/where is this NR_POLES parameter? I can’t find any reference of it in Ardupilot Wiki nor general Googling.
No parameter named NR_POLES that I know of. However there is the SERVO_BLH_POLES parameter that is commonly used to set the number of poles on a brushless motor.
google “brushless motor number of poles”
The correct number is on the datasheet of the particular motor you are using.
Oh I’ve already set SERVO_BLH_POLES to 14 per motor spec. I just wanted to make sure there isn’t a specific “NR_POLES” parameter we need to set somewhere. Thanks for the clarification.
Hello Andy! I also had a lot of questions about the notch filter. I have a 4-stroke engine with one cylinder, that’s one piston stroke in two revolutions of the crankshaft. I could post a question on the notch filter on the forum and wait a long time for an answer that may be useful or not. However, there is a better option, I advise you to start the engine and evaluate the impact of the notch filter yourself. You can assign filtering parameters and analyze the result. No advice is a substitute for testing an aircraft with an engine. I wish you the best of luck and watch my video. I did the tests in my garage, I didn’t disturb anyone with the loud sounds of the exhaust of the internal combustion engine. I advise you to do the same. https://www.youtube.com/watch?v=AQiPJD4W3Kw
ArduPilot Filter Review (youtube.com)
thx, alex.
yep. i’m studying the notch filter documentation and forums right now. i see what you mean about just getting into it. i’m slowly gaining an understanding of the concepts with reading whic, i hope, will save some time in the experiments.
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btw, i think what you intend to mean is that the 4 stroke has 1 FIRING for 2 prop rotations… the 4 stroke engine actually has 2 piston “strokes” on EVERY crankshaft revolution, as does the 2 stroke. a “stroke” is considered to be a single direction of the piston (as in up, or down). the “4” means that it takes 4 strokes (2 up, 2 down) of the piston (2 crank rotations) to accomplish the intake-power-exhaust cycle. a 2 stroke engine takes 2 “strokes” (1 up, 1 down) of the piston (1 crank rotation) to accomplish the intake-pwr-exhaust cycle.
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… and to that point, my reading still needs practical accompaniment, but it seems at theis point in time that the notch filter does not care about how many times you engine fires per revolution. it’s beginning to look, at this point, like the rpm is just used to scale up the notch frequency with increased rpm (from the sensor) after the frequency has been determined and filtered. so 2 strok, 4 stroke, 5 cylinder, etc doesn’t matter.