Published July 16, 2022 © GPL3+

Custom Plywood UAV

Quadrotor made out of laser cut 3mm plywood as a test aerial platform

IntermediateWork in progress819

Things used in this project

Hardware components

Omnibus Airbot F4 v6

Matek Systems FCHUB A5 PMB

Emax XA2212 12V DC 1400KV

DYS DS20A 20amp BLHeli_S 2-4S ESC

6040 Plastic propellers CW/CCW Set x 2

FlySky X6B

RFD900

FlySky i6 Transmitter

Teensy USB 3.2 Development Board

Software apps and online services

BetaFlight

Hand tools and fabrication machines

Soldering iron (generic)

Solder Wire, Lead Free

Cable Tie

Story

I wanted to prototype a quadrotor frame out of laser cut plywood. This was also my first attempt at making a drone from scratch (for later addition of a action camera for in-flight footage/basic aerial photography). A full design process was followed - conceptual design, thrust-weight ratio calculations, weight/cost budget, CAD etc

CAD Assembly

Designed the parts for the laser-cut DXF files using AutoDesk Fusion360. My chosen material was 3mm plywood. The various parts slot together as inspired by ideas at http://www.shendrones.com/booboo. The parts are described as follows:

Chassis Upper x 1
Chassis Lower x 1
Motor Pad x 4
Legs x 4
Rotor Arm x 8

Fabrication

The CAD files were then converted into DXF for use on the university laser cutting machine

Assembly

The assembly of the drone required some fasteners (only 4 x standoffs and shock mount hardware) with the usual flight controller footprint. The rest was glued together using wood glue.

Component Selection

A major part of a successful (and flyable) quadrotor is the thrust-weight ratio which essentially is a measure of how capable the drone is to hover and remain manouvreable. For an aerial photography platform, a thrust-weight ratio of 2:1 is sufficient (see https://www.dronetrest.com/t/how-to-choose-the-right-motor-for-your-multicopter-drone/568 for more details). Explanations of my calculations are below:

The weight of the entire drone (battery, assembled frame, motor + props) was found to be 0.531 kg.

From the spec sheet for my motor, the BE1806 2300kV motors provide 0.521kg of thrust at 100% throttle.

So the total available thrust is 4 x 0.521kg = 2.084kg at 100% throttle

To hover, the minimum available thrust should be 0.531kg, so the usable thrust is then 2.084 / 0.521 = 3.9. This means that the thrust to weight ratio is 3.90 which would result in quite an agile drone.

Flight Testing Gear

The flight transmitter was a FlySky FS-i6 (https://www.flysky-cn.com/fsi6). Instead of using the provided FS-iA6B receiver, I decided to use the iBus capable FlySky FS-X6B Receiver (https://img.banggood.com/file/products/20160924022953FS-X6B%20Receiver%20User%20Manual.pdf) to future-proof the design.

Flight time was around 12 minutes using a Turnigy 4000 mAh 3S LiPO

Failsafe Design

Due to the fragile nature of the quadrotor frame, I also tested out a failsafe system that could be used to deply a small parachute, using onboard Teensy/RFD900 setup - as another feature for this drone (Work in progress still...)

Failsfe- Airside

Failsafe - Ground Side

Drone Flight Controller Setup

The Flight Control software I decided to use was Betaflight. This allowed me to set up the PID tuning parameters, iBUS settings and ESC calibration/settings. Majority of the basic set up for the gyro orientation and IMU placement were followed as found on https://blog.dronetrest.com/omnibus-f4-v6-flight-controller-guide/

Motor/ESC Setup

Motor configuration was the conventional Betaflight method for an X frame quadrotor. ESC calibration and direction changes were done through Blheli Configuration (https://chrome.google.com/webstore/detail/blheli-configurator/mejfjggmbnocnfibbibmoogocnjbcjnk?hl=en)

Motors 1 and 2 were CW (as seen from above)
Motors 2 and 3 were CCW (as seen from above)

https://fpvfrenzy.com/betaflight-motor-order/

Flight Modes

The main flight mode that would be used is 'Stabilize' mode. I also set up one Switch as an 'Arming Switch'

Schematics

Code

// Teensy + RFD Failsafe (Ground Side)

#include <PulsePosition.h>
#include <PulsePositionIMXRT.h>
#include <Bounce.h>

#define BUTTON 12
#define PPM_OUT_PIN 9
#define LED 13

// Instantiate a Bounce object with a 30 millisecond debounce time
Bounce bouncer = Bounce( BUTTON,30); 

char channelArray[48];
PulsePositionOutput ppm_out(RISING);

void setup() {

  Serial.begin(115200);
  
  ppm_out.begin(PPM_OUT_PIN);

  pinMode(BUTTON,INPUT);
  
  pinMode(LED,OUTPUT);
  digitalWrite(LED,HIGH);

  delay(1000);
}

void loop() {  

  // Update the debouncer
  bouncer.update();
   
  // Get the update value
  int value = bouncer.read();
   
  // Turn on or off the LED
  if (value == HIGH) {
    digitalWrite(LED, HIGH );    
    ppm_out.write(1,2000);
    delay(500);  
  } else {
    digitalWrite(LED, LOW );
    ppm_out.write(1,1000);
  }
  
  delay(50);  
}

// Teensy + RFD Failsafe (Air Side)

#include <PulsePosition.h>
#include <PulsePositionIMXRT.h>

char channelArray[112];
PulsePositionInput ppm_in(RISING);

#define PPM_IN_PIN 9
#define LED 13
#define SERVO_PIN 3
#define RESOLUTION_ADC 1024
#define PWM_FREQUENCY   (50.00) 
#define PWM_PERIOD      (1000000.0 / PWM_FREQUENCY)
#define PWM_RESOLUTION  (1024)

void sendPWM(float pwmMicroseconds)
{
  float outVal = (pwmMicroseconds / PWM_PERIOD) * PWM_RESOLUTION;
  analogWrite(SERVO_PIN, round(outVal)); // regular PWM
}

void setup() {

  Serial.begin(115200);

  ppm_in.begin(PPM_IN_PIN);

  analogWriteResolution(10); //2^10 = 1024
  analogWriteFrequency(SERVO_PIN, PWM_FREQUENCY);  
    
  pinMode(LED,OUTPUT);
  digitalWrite(LED,HIGH);

  delay(1000);
}

void loop() {     

  if (ppm_in.read(1) >= 1900 && ppm_in.available() > -1)
  { 
    sendPWM(2000.0);
    delay(500);
  }
  else
  {
    sendPWM(1000.0);
  }
  
  sprintf(channelArray,"CH Avail: %d, PPM CH1: %0.2f\n",ppm_in.available(),ppm_in.read(1));  
  Serial.print(channelArray);
  delay(50);
  
}

Credits

Jonathan Loong

2 projects • 3 followers

Mechatronics Engineer | UAV Enthusiast

Contact

Comments

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Custom Plywood UAV

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

CAD Assembly

Fabrication

Assembly

Component Selection

Flight Testing Gear

Failsafe Design

Drone Flight Controller Setup

Custom parts and enclosures

CAD of Drone Laser Cut Parts

Full Assembly STEP File

Schematics

Drone Block Diagram - POWER

Drone Block Diagram - Flight Controller/IO

Code

Failsafe - Air

Failsafe - Ground

Credits

Jonathan Loong

Comments

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Custom Plywood UAV

Custom Plywood UAV

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

CAD Assembly

Fabrication

Assembly

Component Selection

Flight Testing Gear

Failsafe Design

Drone Flight Controller Setup

Custom parts and enclosures

CAD of Drone Laser Cut Parts

Full Assembly STEP File

Schematics

Drone Block Diagram - POWER

Drone Block Diagram - Flight Controller/IO

Code

Failsafe - Air

Failsafe - Ground

Credits

Jonathan Loong

Comments

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