Kevin's Bi-Copter Thread

[Kevin_Erik]

Found the correct suite: https://blhelisuite.wordpress.com/

[Kevin_Erik]

Got all the electronics installed and working.

Motors Good!

Servos Good

Receiver card Good!

Waldo-Test Good! (Shit spinning the right way ect)

[Kevin_Erik]

@David

My only serious issue with the Bicopter thus far is the placement of the cable pass-thru from the Motors / Servos to the Flight Controller. IMO, it’s a bit too small and is in a rather bad spot. Would of been easier if it were mounted above the Carbon-Arm and 20 – 40% larger. Other then that, I did spend a lot of time figuring out the best way to install the F405-STD / FCHUB. (only like 2-3 of us are using it) Despite the awkwardness of the cards inside the small frame, I rather like how everything is laid out. Didn’t need to solder in the Servo’s at all as i have pin-outs right off the PDB and all the pads for the primary assets are very easy to solder too.

Side Note: I’ve added an extra 5 Volt cable / ground so i can attach a micro camera / TX to the outside of the skin via double-sided tape. Whole assembly is 8-10 grams and has a maximum range of about 30-40 meters.

[Kevin_Erik]

Going to take a break for today and maybe finish it off tomorrow.

[Kevin_Erik]

Finished assembling the Bicopter and did a quick tabletop test of the motors and Servos.

The oscillation started after an RC input was given to change the orientation of the Servos. Once started it runs non-stop until a counter command is given or the copter is disarmed.

After seeing this, I’ve the feeling that the system is a bit overly sensitive. It’s possible that making a black-box log of the event would help in figuring out why.

Note: Combined weight, 570 grams with Ducts and battery. Could shave off another 10-15 grams by trimming the length of the battery cable.

[Kevin_Erik]

Using…

set servo_lowpass_hz = 40

Instantly corrected the above stutter.

Will review the Black-Box logs to see what the before and after logs show. Maybe I can set a specific frequency that’s better suited for the problem.

[jstremmler]

Hi Kevin,

which servos did you use? Did you specify set servo_pwm_rate = 250 in the CLI? Fast digital servos can do up to 330 but BMS servos go only up to 250…. Are timers for motors and servos different? Think you have to adjust PID values for pitch and yaw as well…

Juergen

[Kevin_Erik]

@jstremmler

Using David’s “special sauce” Servo’s and they’re set to 250 but the MFR recommends 240.

Here is my diff…

# version
# Betaflight / MATEKF405 (MKF4) 3.5.1 Sep 8 2018 / 05:31:25 (d9fb5ca13) MSP API: 1.40

board_name MATEKF405
manufacturer_id

# name
name Bicopter

# resources
resource MOTOR 2 B08
resource MOTOR 3 NONE
resource MOTOR 4 NONE
resource MOTOR 5 NONE
resource MOTOR 6 NONE
resource MOTOR 7 NONE
resource SERVO 1 C07
resource SERVO 2 C08

# mixer
mixer BI

# servo
servo 4 1100 1900 1520 100 -1
servo 5 1100 1900 1520 100 -1

# servo mix

# feature
feature -TELEMETRY
feature -OSD
feature -ANTI_GRAVITY

# beeper

# beacon

# map
map TAER1234

# aux
aux 0 0 0 1700 2100 0 0
aux 1 1 2 1300 1700 0 0
aux 2 2 2 900 1300 0 0

# master
set gyro_lowpass_hz = 80
set acc_calibration = -78,28,5
set mag_hardware = NONE
set blackbox_p_ratio = 64
set motor_pwm_protocol = DSHOT600
set align_board_yaw = 270
set servo_center_pulse = 1520
set servo_pwm_rate = 250
set servo_lowpass_hz = 35
set deadband = 9
set yaw_deadband = 9

set dterm_notch_cutoff = 0
set p_pitch = 60
set i_pitch = 45
set d_pitch = 60
set p_roll = 45
set i_roll = 20
set d_roll = 15
set p_yaw = 40
set i_yaw = 20
set d_yaw = 60

[Kevin_Erik]

Here is the Before and After logs. Keep in mind that this is NOT a flight but a bench run to get a feel for how the copter may possibly behave.

Attachments:

1. 

   before.jpg
   

2. 

   after.jpg
   

[Kevin_Erik]

Based upon the noise values shown about I’ll try dropping the Gyro filter to 80 and the Servo LPF to 35.

[Kevin_Erik]

Latest bench test with Filter changes.

[Kevin_Erik]

Did the Maiden flight, only to have the motors shut-off in flight. Luckily the copter was only 2 meters off the ground so it didn’t sustain any serious damage that I am currently aware of. Odds are though the Servos are probably toast.

Will post the Black-box log when i have chance.

[Kevin_Erik]

Update: Had one damaged servo from the crash that needed rebuilding.

[Kevin_Erik]

***Important***

Ensure that you have he following CLI command set to OFF…

runaway_takeoff_prevention

Otherwise BF could disable your motors mid-flight as it did mine.

[Kevin_Erik]

Blackbox log of the Maiden flight is attached.

Attachments:

1. Bicopter-Maiden-9-27-2018.zip

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