Betaflight 3.5 Feedforward - what is it and how to use it!
Betaflight 3.5 is just around a corner and it brings new cool things. There is no more Dterm setpoint weight and Dterm setpoint transition (relaxation ratio). They all were replaced by easier to understand Derivative and Feedforward (Feed Forward when you refer to the control theory tho).
The first one, called Derivative (D gain) is the gain that would be applied with Dterm setpoint weight of 0. While Feedforward is the gain that would be applied at setpoint weight of 1.
The first one, the old Dterm (Derivative) is active always and is responsible for damping any rapid changes. The second one, feed forward part, is active only during stick movements and is responsible for the responsiveness of a drone. You want a sharper response, increase F gain. You want smoother endings, increase D gain. The more D, the smoother everything will be, the more F, the more control you will have.
Also, you do not have to raise P gains to boost responsiveness now. Just boost the feedforward element and you will be fine. Also, since Feedforward is open loop part, it will not induce oscillations or try to destroy your motors! OK, it can, but you would have to move the sticks very very fast to do so ;)