Talk describing my custom quadcopter firmware.

1. QUADCOPTER
FLIGHT CONTROLLER
building & programming a
from scratch

2. I’m Ryan Boland
Web Developer
@ Tanooki Labs
@bolandrm (github, twitter)

4. 1. Components
2. Quadcopter Physics
3. The Flight Loop

5. FRAME

6. Electronic Speed Controllers (ESCs)
& Motors

7. Lithium Polymer (LiPo) Battery

8. Remote Control Transmitter & Receiver

9. Flight Controller
Microprocessor &
Inertial measurement Unit (IMU)

10. My Project - Custom Flight Controller
Arduino Mega 2560
& Prototyping Shield
8-bit AVR
16 MHz clock
256K Flash
8K Ram
Arduino Nano Clone
8-bit AVR
16 MHz clock
32K Flash
2K Ram
Teensy 3.1
32-bit ARM
96 MHz clock
256K Flash
64K Ram
$5$55 $20

11. Custom
PCB

12. Inertial Measurement Unit
MPU6050 - 3 axis gyroscope, 3 axis accelerometer
HMC5883L - 3 axis magnetometer
BMP180 - Barometer
GY-87
$8

13. Flight

14. Configuration: + vs X

15. Orientation
x axis <-> roll
y axis <-> pitch
z axis <-> yaw

16. Maneuvering

17. Stabilization
Rate mode - gyroscopes only
Remote control determines the rate at which the
quadcopter is rotating on any given axis.
Also known as Acro or Manual.
Attitude mode - accelerometers & gyros
Remote control determines the desired angle of the
quadcopter.
Also known as self-level or auto-level.

18. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

19. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

20. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

21. Gyroscope data
Actual rotational rate in °/sec
Remote control data
Pilot’s desired rotation rate in °/sec
Error
Difference between actual and desired rotational rate
e = gyro_rate - rc_rate

22. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

23. 3 errors to correct

24. PID Controllers
(proportional, integral, derivative)
For each axis (yaw, pitch, roll):
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html

25. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

26. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

27. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

28. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

29. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

30. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

31. PID Controllers
(proportional, integral, derivative)
PID for dummies:
http://www.csimn.com/CSI_pages/PIDforDummies.html
Motor Output
Rotational rate (from gyro)
error
e(t)
Pilot
RC
input
3 constants - Kp, Ki, Kd

32. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

33. Maneuvering

34. Flight Controller Code
motor1 = rc_throttle - roll_adjust - pitch_adjust - yaw_adjust;
motor2 = rc_throttle + roll_adjust + pitch_adjust - yaw_adjust;
motor3 = rc_throttle - roll_adjust + pitch_adjust + yaw_adjust;
motor4 = rc_throttle + roll_adjust - pitch_adjust + yaw_adjust;
correcting roll, pitch, yaw

35. Flight Controller Code
motor1 = rc_throttle - roll_adjust - pitch_adjust - yaw_adjust;
motor2 = rc_throttle + roll_adjust + pitch_adjust - yaw_adjust;
motor3 = rc_throttle - roll_adjust + pitch_adjust + yaw_adjust;
motor4 = rc_throttle + roll_adjust - pitch_adjust + yaw_adjust;
correcting roll, pitch, yaw

36. Flight Controller Code
motor1 = rc_throttle - roll_adjust - pitch_adjust - yaw_adjust;
motor2 = rc_throttle + roll_adjust + pitch_adjust - yaw_adjust;
motor3 = rc_throttle - roll_adjust + pitch_adjust + yaw_adjust;
motor4 = rc_throttle + roll_adjust - pitch_adjust + yaw_adjust;
correcting roll, pitch, yaw

37. Flight Controller Code
motor1 = rc_throttle - roll_adjust - pitch_adjust - yaw_adjust;
motor2 = rc_throttle + roll_adjust + pitch_adjust - yaw_adjust;
motor3 = rc_throttle - roll_adjust + pitch_adjust + yaw_adjust;
motor4 = rc_throttle + roll_adjust - pitch_adjust + yaw_adjust;
correcting roll, pitch, yaw

38. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

39. Safety & Handling Failure
Stale IMU values
Stale remote control values
Angles too high?
Motor outputs too high? (indoor safe mode)
Watchdog

40. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

41. Wait for data ready interrupt
Read & filter gyroscope data
Read remote control data (user input)
Use PID (proportional, integral, derivative) algorithm
to compute required adjustment for each axis
Map adjustment for each axis to motors (Mixer)
Safety checks
Output to motors
Flight Loop (1000 Hz)

42. Some Takeaways
Be Safe
Start small (mini quad
or balancing robot?)
Break things down
into subcomponents

43. Thanks!
@bolandrm