BF 4.3 Tuning Guide Part 5: Feedforward!

Push your quad into fast moves to keep it tracking setpoint with FF. BF 4.3 enhances feedforward in a number of ways by improving the signal conditioning on the setpoint and adding some feedforward specific filtering.
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[@mikemarucci913]

It’s really nice to have someone like you with these kind of videos in this hobby, these other KZbin guys are great for the hobby but when it comes to technical stuff you are a A1, we are so lucky to have you in this hobby. Chris I cannot say thank you enuf, I’ve been in the hobby for about 3 months now and I’ve learned more in the last 4 days with tuning then prior. Ive been winging it the whole time and your information in these videos make it so easy to understand and grasp, again we are lucky to have you involved and invested in this hobby thanks a million.

[@fpvpf]

I found many answers to my questions in the video.Thx Chris.

[@MurdersFPV]

Love this, Chris. I hope this video will get a lot more pilots to understand and appreciate the value of FF. It's a setting that I feel is underrated on it's impact to your flight feel and control.

[@AlanzFPV]

Thanks for making this Chris!

[@oleg146]

Yay! Thanks a lot for a great video, I understood everything from first attempt!

[@bkfpv]

Great stuff. Thanks Chris.

[@mbug7973]

These preview pics get better and better 😆

[@SupaflyFPV]

Good explanation Chris - it is quite a complex system which needed some documentation. And thanks for Chris Thompson AKA CTZsnooze for the developments of Betaflight featured in this video. It is a lot of work to code and test this stuff!

[@thfpv4974]

Great video Chris ty 😊 🥂🥂🥂

[@pmantix]

Great video Chris 👍🏻 I’ve noticed that when I’m satisfied with my tuning of betaflight’s FF and D term it looks a lot like I’ve basically taken the scenic route route to making a synthetic d/dt error term. Meaning in a blackbox log, the FF term + D term is almost equal to what would be d/dt error once the quad is “well tuned” by my reckoning. I don’t know the history of how Betaflight (or cleanflight perhaps) came to the decision to separate the typical d/dt error term into d/dt setpoint and d/dt gyro, but I was curious about this - so I decided to do some experimenting on my own in simulink. Even with setpoint and gyro signals operating at different sampling frequencies, having different noise characteristics, and having different disturbance characteristics, I could not find a clear benefit for separating d/dt error into these multiple terms. I was getting better simulated setpoint tracking with simpler tuning using the standard PID controller and the standard definition of the D term (where D = d/dt error). Have you ever looked into anything like this? I’m curious to know if other’s have found similar findings, or can counter my findings. Perhaps I’ve overlooked something simple, but my analysis suggests the performance of betaflight’s PID controller could be improved and the tuning simplified if the FF and D terms were combined into the single d/dt error term, as per the norm.

[@MADFlyFpv]

Thanks master Chris¡¡

[@skree_fpv436]

Great video Chris. It's funny, I watched a UAVTech video just before this one where he says RC smoothing is a high performance RC link killer and suggests turning it off.

[@tonhabraken9339]

Saw that too. Tad bit confused now. Haha

[@alvestecnologia4429]

It is two different situations, on uavtech video, the main focus is racing e reduce latency. On this video, the propose is more general, criss talks about racing, freestyle, cinematic,..

[@ChrisRosser]

Alves is spot on. RC smoothing adds delay to the link. In general pilots find a lot of smoothing good for cinematic flying but for racing minimum delay is typically the goal.

[@pohoronshic]

The BEST👍👍👍

[@PKNEXUS]

Awesome!

[@Atlas_FPV]

Nice video, very interested in playing with throttle smoothing to see what impact that has.

[@JanRispens]

Make sure to set deadzone to 0! Feed forward will explode around center, had a lot of fun finding my random twitch source. Don't know if this is a 4.3 problem.

[@ero6760]

D term is also calculated by error , then pass to D term filter and gain

[@TimeFadesMemoryLasts]

The BF D-term is actually just calculated from gyro change over time. The setpoint change over time is used for feedforward. In BF, Feedforward and D-term are split up (in a "normal"/classical PID controller FF is incorporated into D-term and the FF gain is locked to the D gain). Splitting up the error into D-term and Feedforward and giving Feedforward an additional independent gain opens up a whole new dimension for flexibility in PID tuning.

[@userunknown2771]

ffd was in deed set to high at 1.0 for my AOS 5.5. I turned it down to 0,95 and now its perfect. really close tracking at start and the lines just touching at the end of a move. my other settings are. Master: 1,8 I-Gains: 1,5 FF-Gains: 0,95 D-Max: 0 (all other at 1.0)

[@ezalku]

is there any setup in betaflight 4.3 for deadcat frame ?

[@serval_fpv]

Where is these UAV tech trace templates ? Ok found some stuff on his site but there's so many not sure what's needed ?

[@ZicmuMr]

Hello Chris. Your knowlege is priceless. Can you discover the magic hidden behind curved magnets in motors? Like in new Iflight Xing 2 or Mr Steele's new V4 motors?

[@ChrisRosser]

Curved magnets are used to reduce the average air gap between the rotor and stator. This increases the field strength in the air gap which provides more torque.

[@ZicmuMr]

@@ChrisRosser I see. What about new Xings and their „New center slotted N52H curved arc magnets”? Those center slots looks like there is more space between magnet and coil in center spot.

[@alfoncebrun6798]

Hello, thank you a lot for the serie of video. I follow all video and all are nice and smooth but I have always the dynamique D slider at 0. I leave it at 0, default position or need to tune it?

[@ChrisRosser]

You can leave it at 0 👍

[@martinchristiansson658]

Why is rc smoothing using a third order filter rather than a first or second? Why is this particular benificial? Thanks!

[@ChrisRosser]

A third order filter has a steeper cutoff which is beneficial when you want to preserve low frequency information whilst eliminating the stepping signal.

[@martinchristiansson658]

@@ChrisRosser ok thanks, I guess it is because the step/impulse is containing alot of higher frequencies (fourier sum)

[@TimeFadesMemoryLasts]

@@martinchristiansson658 exactly. It's a zero-order hold signal that needs to get filtered in a way to have as little delay as possible while still having strong enough filtering to get rid of the high frequencies from the steps.

[@1911doc]

Today put first time BF 4.3 on my quad, micro apex 4" and have some weird problem that I cannot takeoff normally. Quad arms as usual, no funny noises and when you want to takeoff quad goes like 5cm in the air and just wont go higher, even if I put 100% throttle it will just hover 5cm from the ground. It feels like some flying mode is active that prevents me to fly normally...Just to mention, on BF 4.2.11 quad flew normal, just needed a tune. Watched today all BF 4.3 videos from you because wanted to tune my new micro apex 4" and discovered this problem when I went out flying to record blackbox. Do you have any idea what that could be? Thanks a lot!

[@oleg146]

you made a clean install?

[@1911doc]

@@oleg146 Ofc, and applied custom setting for FC. No tweaking was done, wanted to do blackbox log for tuning on stock BF settings. Also my friend told me he had the same issue on his Flywoo Firefly and he just went back to 4.2.11 and quad worked normally.

[@TimeFadesMemoryLasts]

@@1911doc Try RC4. RC3 is 2 months old.

[@oleg146]

@@1911doc oh i see, wow, sounds weird! What blackbox shows?

[@1911doc]

@@TimeFadesMemoryLasts Already have it, did all the latest install of the betaflight configurator with RC4.

[@mirekfpv4267]

Where can I download BBE trace presets?

[@ChrisRosser]

From Uavtechs Google drive. tiny.cc/uavtech

[@mirekfpv4267]

@@ChrisRosser thx 😁👍