FPV Sampa

How to use Dynamic Notch Filter in BetaFlight 3.2+

Um dos recursos mais legais da nova versão 3.2 do BetaFlight é o Filtro Notch Dinâmico. Este filtro permite fazer o drone voar de forma muito mais estável e suave, além de eliminar pequenos problemas de vibração. Mas para usar o recurso, você precisa entender o que é o Filtro Notch, afinal ele é muito importante e configurá-lo de maneira incorreta pode danificar os motores do drone.

O que é o Filtro Notch?

The Notch filter is a kind of damper, which serves to smooth the speed changes commanded to each engine. The flight controller sends the desired speed to the motors hundreds of times per second to the ESCs. If the speed difference between one command and another is too big, the ESC will literally slow down and accelerate the motor continuously. As this is repeated several times per second, the result is vibration caused by the motors.

The Notch Filter prevents this by not allowing abrupt motor speed changes. It evaluates the latest N samples and only sends an average to the ESC, so that each received command will not be very different from the previous command.

The problem with this approach is that it causes lag. In order for the Notch Filter to send a value to the ESC, it needs to receive several values ​​from the controller before, then calculate the average and send. This delay of the order of milliseconds is enough to affect the drone’s handling and stability, so it’s a good idea to try to minimize the application of the Notch filter.

But the Notch filter is important! After all without it the engines will fry due to constant acceleration and deceleration. The dynamic Notch filter came to solve this problem, as it will only act on the required minimum frequency, leaving the PID algorithm to take care of drone stability in a more direct, and therefore faster, way.

Precautions

To enable the Dynamic Notch Filter and have satisfactory results, you should disable the other Notch Filters available in BetaFlight (they are 3 in total). But you can not just disable them without first taking some care. Remember! Without filters you will fry the motors!

You should try to eliminate vibrations from your drone, in order to make the controller’s gyro receive as little vibration as possible. There are several ways to do this:

  • Mount motors with soft uprights (silicone or rubber)
  • Mount the controller with soft uprights (silicone, rubber or foam)
  • Use good quality propellers, with good balancing, new, not damaged
  • Use good quality, balanced, undamaged motors
  • Try to center the battery weight in the middle of the drone

Another important tip: Always use the latest firmware version of the ESCs. Try using the DShot300 or DShot600 protocols.

Procedure

  • Assemble the controller in soft-mount
  • Return to standard BetaFlight PIDs
  • Enable Dynamic Notch Filter
  • Switch the D Lowpass Filter to PT1
  • Take off and hover for some time, then check the temperature of the motors
  • Fly a little and check the temperature of the motors
  • Set Gyro Notch Filter 1 Frequency to 0
  • Fly a little and check the temperature of the motors
  • Set Gyro Notch Filter 2 Frequency to 0
  • Fly a little and check the temperature of the motors
  • Set D Term Notch Filter Frequency to 0
  • Fly a little and check the temperature of the motors

It is important to check the temperature of the motors at each stage, because if something goes wrong, you will have time to see before the motors undergo any serious problems.