Low frequency oscillation

[wynnsquad]

Just went back to 0.7 beta 2 to try what David had suggested to me. Basically I set the PIDs to match those of V4 defaults for 0.5 and I set tri_motor_acceleration, tri_motor_acc_yaw_correction, and tri_yaw_boost to zero.

It flew pretty well and the tail is much better behaved than it was when I tried 0.7 before. When yawing hard to the right and then releasing the stick, the copter stops crisply, while doing the same to the left, drifts a bit. Not nearly as bad as before though.

@biggestRCEfan, how are things going with 0.7 v8 with the new yaw control? If its working well, I’d be interested in giving it a go. Could you provide me with a diff of your setup?

[biggestRCEfan]

Siclair, 0.5 is where we are coming from. Works well but there are other reasons to move to 0.7, including the simple reason that cleanflight Configurator (old version, needed lo run 0.5) keeps disappearing out of Google Chrome. In 0.7 with betaflight I am able to use Lua script on my Taranis to adjust PIDs and rates without hooking up the laptop. Another BF Configurator advantage is the diff function. Keen to know when triflight will merge back into BF, to access newer features.

Wynn, 0.7 beta 2 worked fine, except sudden yaw inputs caused jumps in pitch. Could have solved it with playing with the parameters you refer to but never tried. On Layla’s advice I went to V8 of the alpha code, which flies like a dream. Still playing with the PIDs on the yaw channel as it is not as crisp as for pitch and roll. Regarding low frequency oscillations I flew in strong, gusty wind (15km/h) on the weekend and hardly noticed any oscillations. Will post my diff later in the week.

[biggestRCEfan]

Wynn, here is my diff:

diff
# Triflight 0.7 Beta 2 – new control test v8 / RCEXPLORERF3 3.1.7 Sep 10 2017 / 11:15:56 (ca5d4df)
servo 5 1000 2000 1446 40 40 100 -1

feature MOTOR_STOP
feature TELEMETRY
feature CURRENT_METER
feature BLACKBOX
map TAER1234
serial 1 32 115200 57600 0 115200
serial 2 128 115200 57600 0 250000
aux 0 0 0 1700 2075
aux 1 28 1 1675 2075
aux 2 1 1 1300 1675
aux 3 31 2 1300 1700
rxfail 3 h
rxfail 5 s 1500
set min_check = 1010
set max_check = 1990
set debug_mode = NONE
set min_throttle = 1050
set motor_pwm_rate = 400
set align_board_pitch = 180
set gyro_lpf = 188HZ
set moron_threshold = 32
set deadband = 10
set yaw_deadband = 10
set servo_pwm_rate = 250
set tri_tail_motor_thrustfactor = 61
set tri_tail_servo_speed = 242
set failsafe_delay = 8
set failsafe_off_delay = 200
set failsafe_throttle = 1250
set failsafe_procedure = AUTO-LAND
set baro_hardware = AUTO
set pid_process_denom = 1
profile 0

set yaw_accel_limit = 10.000
set p_pitch = 97
set i_pitch = 26
set d_pitch = 25
set p_roll = 105
set i_roll = 30
set d_roll = 25
set p_yaw = 180
set i_yaw = 35
set d_yaw = 35
set p_level = 20
set i_level = 10
set p_vel = 120
set i_vel = 45
set d_vel = 1
rateprofile 0
rateprofile 0

set rc_rate = 130
set rc_rate_yaw = 165
set rc_expo = 85
set rc_yaw_expo = 83
set thr_expo = 90
set tpa_rate = 0
set tpa_breakpoint = 1500

#

[Siclair]

The tricopter always had problems with the yaw. The tricopters are nice flying machines and look way better in the air but the resent progress on the FC and their firmwares like betaflight leaves the tricopter in the dust.

Flying my 400 mm quad with betaflight is like flying a missile. The tricopter is still nice and have its place but it’s not comparable to the quad. Like apples and oranges.

I tried the 0.7 and it flew like xxx. Played abit with the pids and got it flying much better but I never had the patience to tweak the pids and all the other parameters to my liking.
Sorry for hijacking the thread. Good luck.

[biggestRCEfan]

The good thing about this hobby in modern times is that I found someone with the same problem and we are working the issue together. The one is in the US and the other in Australia. I don’t have to wait to ask someone at the club on the weekend.

I started with tricopters because they intrigued me. I own all three from David’s, after the first one being the FT Electrohub with wooden booms and naze FC. Built my first quad recently. Yes, quads are more agile and precise. And more robust.

The progress Lauka has made is fenomenaal. The V8 firmware is getting very close to the polished product we want.

Love this hobby!

[wynnsquad]

RCEfan, Thanks for the diff hoping to try out v8 tomorrow and report back!

[wynnsquad]

RCEfan,

Tried V8 and many of your settings, and it’s working pretty good! Thanks again for the diff. It seems like I’m seeing some of the same tendencies that you are seeing. I posted my diff and flight experience over on the new yaw thread here

As far as the oscillation goes, it’s definitely still there for me but it might be slightly less now. Will have to continue trouble shooting that now but I’m hopeful that betaflight will have all of the necessary ‘knobs’ to tune it out. I’m particularly interested in playing with the notch filter but I need to get a data-logger first.

[biggestRCEfan]

Just an update by way of a video flying my V4. There is minor jello which I am going to try to get rid of by using 6x3x3 props. Will see if that helps. But I am quite happy with what I have in the V4 as a chase drone/cruiser.

Check out the https://youtu.be/TgEGRPBI7eU. [Where did the link button go?]

[wynnsquad]

Looking good RCEfan!

That’s an interesting idea to go to a 6 inch tri-blade prop. Do you think that it will provide similar thrust and current draw as compared to the stock 8″ blades?

As far as tuning/settings go, what do you feel has made the biggest difference in improving your oscillations so far? What are your current PID’s?

[biggestRCEfan]

Update: I fitted the V4 with 6x4x3 props (not the 6x3x3 I stated earlier). I think it improves the quality of the HD footage.

Here is some footage: https://youtu.be/76wTnOVyPzQ

Wynn, I haven’t changed any PIDs as yet (see my settings above in an earlier post in this thread). But clearly the performance and handling is not good enough. On a 2200mAh 4S I get around 8 minutes, the hover throttle position is about 75%, and response is sluggish. I should increase rates to address this. Current draw in the hover is around 14 Amps (can’t recall what is is with the 8×5 props) and motors and ESCs are handling it well.

Next step is to fit 7×3.5×3 props I have on order, which hopefully would be closer in thrust to the 8×5 props at similar power settings.

Once I am happy with the performance and overall handling, I will start working on rates and PIDs. I believe the image quality can further improve with tightening the PIDs loop gains.

[wynnsquad]

I would agree that the HD looks very nice with the 6 inch props. I’m interested to hear about performance with the 7 inch.

Here’s a video of one of my recent flights. Having lots of fun but the infamous wobble is definitely present. I’ve been experimenting with gains but I believe this flight was on default PIDs (maybe slightly higher on P and D).

I’ve also been doing some experimenting with props. But I’ve gone bigger. The flight below is with 9×5. I thought I’d try slightly bigger because I fly at higher altitude (~5000 ft).

[biggestRCEfan]

Nice. You have a nice area to fly! What camera and settings are you using? GoPro. The image is good.

I decided to go to 3-bladed props to increase the frequency and see if that improves things. Hence the smaller props. Somehow I don’t have the whole as much anymore. From memory I think the PIDs made the difference. Will see how we go when I start playing with them again.

[Kevin_Erik]

I know the V4 frame is an extension of the Mini-Tri but 14 Amps draw sounds like allot at hover… I see 7.6 Amps using 6×4.5x3RS Props, 35A-ESC’s and F80 motors. On a cold day i can get 8 minutes of hard flying or 10ish when the weather is nice.

Note: Flight weight with 1800mAh battery is 650-670 grams.

[Kevin_Erik]

Check this video out as it sounds allot like what you may be experiencing: https://m.youtube.com/watch?v=PHkofDq_JxU

I.E. Too much filtering adds excessive delay, while causes the copters to constantly overshoot and then attempt to compensate. Hence oscillations.

[wynnsquad]

RCEfan,

It is a really fun place to fly. The 3D environment makes things fun. As far as camera goes, it’s just a Mobius action cam at 1080p 30 fps. I used to have jello but then I switched to loosely mounting my camera with some Velcro on the bottom, and a loose strap around it.

Kevin,

Thanks for the tip! I’ll look into that.

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