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Improve Liftoff flight!

Improve Liftoff flight!

The one flight controller setting you have to try in Liftoff, according to Joshua Bardwell.

Joshua Bardwell, the FPV know-it-all himself recently published a video about D Setpoint weight and D Setpoint transition, two parameters that you can adjust in the PID tuning window in Betaflight. According to him, the default values used in Betaflight are an error, and could be the reason why Betaflight can sometimes feel a little sluggish compared to other flight controller firmware. The great thing about these parameters is that we also have them in Liftoff, and they work in a very similar way. So you can definitely try tweaking them on your favorite simulator first, without risking your quad, and see if it’s worth the try!

If you have not seen his video yet, check it out here.

 

So, what is D Setpoint?

As you may know, the D gain of a PID controller can be seen as a dampener. It counteracts the oscillations that could happen after a very sharp maneuver because of the P gain. As a side effect, excessive D gain can make the quad a lot less responsive, resulting in a sluggish flight sensation. Oscar Liang talks about this in more detail.

Betaflight can use two methods to derive D value: derivative of error, which gives a very sharp stick response but can make motors hotter, and derivative of measurement, which gives a very soft stick response.

With a D setpoint weight of 0, Betaflight uses only the derivative of measurement method, resulting in a sluggish stick response. With a D setpoint weight of 1, it uses only the derivative of error method, resulting in a sharp stick response. Intermediates values work as a balance between the two methods. Over 1, you get increasingly sharper response, but the flight sensation might get awkward.

D setpoint transition allows you to use different values of D setpoint weight depending on the stick position. If set to 0, the setpoint weight will be constant whatever the stick position; if set to 1, only the stick endpoints will use the D setpoint weight configured. As a result, a transition at 0 would give you a very aggressive response, while 1 would give a mushier response.

 

 

What should you do with your D setpoint?

It all depends on the kind of flight sensation you are looking for, but Joshua Bardwell includes some suggestions in his video, aimed at getting an overall sharper stick response:

Betaflight Default values:

  • D setpoint weight = 0
  • D setpoint transition = 1

Joshua Bardwell suggestion:

    • D setpoint weight = 1
    • D setpoint transition between 0.01 and 0.2*

 

TL;DR