jstremmler's bicopter

[jstremmler]

After solving my problems with the servos today, I did a successful maiden flight and was flying 3 1500mAh packs afterwards.

Here is my equipment:

1 Bicopter frame from RCExplorer
1 RX Hitec Optima D in SBUS mode
2 Servos BMS 21HV
2 motors EMAX 2205 2300kv
2 propellers Racerstar 5048
1 OmnibusF4 Pro corner FC
1 external BEC 5V and 6V 7A
2 32 bit BLHEli_32 ESC’s 30A
4 FC softmounts from Realacc
4 1500mAh 4S1P Infinity lipos 90C

Servos are connected to M5 and M6 soldering pads on the FC, resources for motor 3,4,5,6 are set to none, mixer to bicopter and UART1 to SBUS. I did 32k/16k sampling, 216MHz overclocking and use DSHOT1200 for the ESC’s. Rest of parameters and PIDs were taken from David’s file.

I use the sOAT principle like jihlein as you can see from my foto but have oriented the servos to the front of the bicopter. Buildt a simple scale for the CG of the bicpter to adjust for different batteries when flying.

Flight characteristis in forward flying is good but still needs some tuning.
Flight characteristics of my bicopter in backward flying is bad, but it flies backwards!

Only real problem is landing the bicopter. If one does this too smoothly the bicopter is shaking like a bronco.

Next action will be to ad the speedybee bluetooth adaper because it’s a pain in the … to disassemble the copter just for changing one flight parameter in the field.

Juergen

• This topic was modified 5 years, 1 month ago by jstremmler.
• This topic was modified 5 years, 1 month ago by jstremmler.

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[Kevin_Erik]

The Bicopter is somewhat nose heavy so I’d suggest mouning the OAT so that the Servos are aft of the carbon bar. This will allow for more weight rearward as well as protect the servos from a forward impact. Keep in mind that the battery can always be slid forwards to adjust CG but not backwards with that support in the way.

What are you using BF or Bi-Ronin?

[jstremmler]

Posted already, that my main purpose mounting the servos to the front is to support the servo industry. Wont change that anymore… btw to change that would cause a complete rebuild of the bicopter. My 7A BEC has been mounted in the back of the bicopter and battery had to be placed over the support to meet the CG. Actually I am flying Betaflight 3.5.2 #30 but plan to change to Dronin and change FC to my Sparky2. But I will do that only when my bicopter flies awesome in all directions…

• This reply was modified 5 years, 1 month ago by jstremmler.

[Kevin_Erik]

Just saying as CG is seriously important.

[jstremmler]

Yesterday I had a failsafe with my bicopter because of low RSSI. Maybe both 2.4 GHz antennas were in a flight position where the were right behind the CF frame??? Think I shoudn’t just let them hang our of the back of my bicopter…
Any suggestions?

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[jstremmler]

Will simply try this now:

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[jstremmler]

Here is my actual diff_all:

Attachments:

1. Diff_all_corner.txt

[jstremmler]

Today I tested Kevin’s PID values:

Roll P=26 / I=8 / D=45 / FF=173
Pitch P=40 / I=8 / D=55 / FF=211
Yaw P=100 / I=10 / D=40 / FF=100

Think, with these settings the bicopter in much to spongy. It is flying like my big quads I built 6 years ago. Personally I prefer David’s PIDs much more. The bicopter flies out of the box much better with these PIDs (except flying backwards and landing).
But maybe there is a solution inbetween. So tomorrow I will fly my own PID’s and will see how the bicopter flies with them:

My Defaults P I D Feedforward RC Rate Super Rate RC Expo

Roll 46 45 33 127 1,55 0,73 0,20
Pitch 50 50 38 146 1,55 0,73 0,20
Yaw 65 45 0 100 1,00 0,75 0,30

• This reply was modified 5 years, 1 month ago by jstremmler.

[jstremmler]

Was testing my Default PIDs today… (these are the ones with which I start flying every new 5″ quad)

Unfortunatey we had strong wind with gusts up to 40 miles/hr so my test results from today are not representative. But flying against strong wind and releasing the pitch lead to strong pitching up of the bicopters nose.

For my next flight I will make the following changes:

1. Increase P for pitch from 50 to 55.
2. Decrease RC Deadband and Yaw Deadband to 1
3. Increase RC Expo for Yaw to 40
4. Switch off Feedforward Transition (= set it to zero)

Hope we will have less wind tomorrow.

[Kevin_Erik]

Be aware that on the PID tunes i was working on, i had Feed Forward enabled. Thus the rates don’t behave like they normally would. Hence the spongy feel…

Beyond that, preventing P-Term overshoot and oscillation on Pitch / Yaw is the only way to keep stability during tight turns or reverse flight.

[jstremmler]

@Kevin
as you can see from my “diff all” my Feed Forward was enabled as well when trying your PID’s. Only difference that might have been active was a FF transition of 0.2 which I have now switched off.
Having been worldwide mentor for Advanced Controls from the TMN (Technical Managhers Network) within BP plc for many many years I doubt, that preventing any P-Term overshoot of a PID loop for a multicopter is the best strategy to tune it.
Btw with the sOAT configuration I don’t have any oscillations on Yaw.

[Kevin_Erik]

The Feed-Forward affected how my tune came out. Had it been off, the results would of been better. Same is true for anying that changes your I-Terms as the Pitch / Yaw appear to be especially sensitive to this.

Now as for the overshoot, yeah on a normal quad and to some extent a Tricopter what you said is true. However with the Bicopter, the servos are too slow to adequately correct for excess overshoot. Thus its better to prevent it then to try to compensate for it.

Have you considered that because your using OAT that someones non-OAT tune wont work well for you?

[jstremmler]

@Kevin
“Have you considered that because your using OAT that someones non-OAT tune wont work well for you?”

Sure, but I made a terrrible building mistake (was too penurious), when utilizing my defective (5V rail + SD-cardreader) Omnibus F4 corner for this experimental bicopter. As a result I cant record flight data on my SD-Card. Will change that when my speedybee bluetooth adapter arrives.

[jstremmler]

For those of you who have to place their battery over the support to meet the CG I have drawn a small wedge for avoiding to damage your battery during landing. You can just sclice it and print it with your 3D-printer. Length is appropriate for a 1500mAh battery.

• This reply was modified 5 years, 1 month ago by jstremmler.

Attachments:

1. keil.zip

[jstremmler]

Back in the business!

Finally got my SpeedyBee bluetooth adapter and installed it. Configured it on motor 5 for switching on/off when arming.

Required CLI commands:

set pinio_config=129,1,1,1
set pinio_box=0,255,255,255
resource motor 5 none
resource pinio 1 A01 (only valid for my OmnibusF4 Pro corner)

Same time I decided not to support the servo industry anymore and have changed the orientation of the servos-
They are now oriented to the back of the bicopter. Just like it should be, but now unfortunately the back of my battery sits in the middle of the back support when the CG is ok.

• This reply was modified 5 years, 1 month ago by jstremmler.
• This reply was modified 5 years, 1 month ago by jstremmler.

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