1. Stanford APM:Plane Overview
Trent Lukaczyk
April 7, 2014
AA241X – UAV Design and Build

2. Airframe Construction
The Problem
Fly Autonomously
Airframe Construction
State Estimation
Algorithm Processing
Control Actuation
Ground Monitoring

3. The Components Autopilot Unit Wireless Telemetry Remote Control Radio
GPS Radio
Compass Magnetometer
Airspeed Sensor
Battery Monitor
Servos, ESC, Motor

4. Autopilot Unit Auto Pilot Module (APM) ArduPilot Mega (APM) 2.6
Based on Arduino
16MHz Atmega2560 processor
16 MB dataflash memory
~ 2hours of logging (download often)
Needs: to point forward to be securely attached accelerometer calibration if relocated

5. Wireless Telemetry Wireless Telemetry 915 MHz, 100mW Shares a “NetID”
“MAVLink Protocol”

6. Wireless Telemetry
USB Micro B
DF13 6-Pin
DF13 5-Pin
USB A

7. Lift this lip gently with a screwdriver
DF13 Connectors
Lift this lip gently with a screwdriver
Pain and a Half to use
Easy to break
But small, reconfigurable
Be careful when disconnecting!
Can shave these hooks off with a knife
Can add hot glue at the wire-connector joint.
Do not use super glue here.

8. Radio Control Setup RC Transmitter, 2.4 GHz “Binds” with Receiver
Always carry the bind plug
Four axes + mode switch
Turn on first, before plane
Autopilot Mode Switch

9. Radio Control
3pin Servo Wires x5

10. The order of these vary with receiver
Radio Control Setup
Autopilot Mode Switch
The order of these vary with receiver

11. Servo Wires
Mixing up signal and ground can fry electronics Look for markings like this -

12. GPS + Compass 1.57 GHz GPS radio Magnetometer 5Hz position update
Needs clear sight of sky
Magnetometer
Provides heading estimate
Needs to be clear of high-current electronics
Needs: to point forward
calibration if relocated

13. DF13 6pin GPS DF13 4pin MAG DF13 4pin DF13 5pin
Remember to point GPS and APM forward

14. Airspeed Sensor
Pitot tube measures difference in “Static” and “Total” pressure, which is related to airspeed.
Airspeed is relative to wind
will be higher or lower if you travel against or with the wind

15. Airspeed Sensor
Silcone Tubing
3pin Servo Wire A1

16. Power Module Records current and voltage from battery
Integrate for energy usage, and battery level
Powers APM, Receiver, Radios, and Servos

17. Lithium Polymer Batteries
3.7 Volts per Cell
Metrics:
N-Cells (2S = 2 Cells = 7.4V)
Capacity (C = 1100 mAh)
Discharge Rate (25C = 27.5A)
Charge Rate (2C = 2.2A)
Can catch fire or leak during charging
Always be present during charging
Capacity loss or Bricking if over-discharged
i.e. leaving plugged in over night

18. LiPo Discharge LiPo’s die suddenly around 3.4Volts/Cell
Be ready to land around 3.5Volt/Cell
traxxas.com
Higher Current

19. Speed Controller Rated by Max Current and Max Voltage
Direct Current Power in, Three-phase Alternating Current out
“Opto” vs “BEC”
BEC can power RC gear, Opto can’t

20. Brushless Outrunner Motor
“Outrunner” - magnets rotate around stator
Rated by kV = no load rpm/V
High kV = fast rpm, low torque
Low kV = low rpm, high torque
Too much power melts windings, burns out motor

21. Power Electronics Setup
DF13 6-Pin
DC Power
DC Power
3 Phase AC

22. Carbon Folding Props More rigid, more efficient, more expensive
(vs plastic props)
More dangerous – they are spinning knives
Spinner cap lets them fold on landing, or if motor braking is on (more efficient glide)

23. Servos Drive Motor + Rotation Sensor + PID Control board … in 8-grams
Forcing the control arms by hand wrecks gears

24. Servo Setup Elevator Rudder 3pin Servo Wires Ailerons Servo Wire “Y”
Throttle

25. The Components Autopilot Unit Wireless Telemetry Remote Control Radio
GPS Radio
Compass Magnetometer
Airspeed Sensor
Battery Monitor
Servos, ESC, Motor

26. Airframe Construction
The Problem
Fly Autonomously
Airframe Construction
State Estimation
Algorithm Processing
Control Actuation
Ground Monitoring

27. Stanford_ArduPlane
An easy embedded flight control software for Aerospace Engineers, based on ArduPlane
ArduPlane code without the control law

28. Development Tools Download and install the ArduPilot Arduino IDE
Download Libraries and place in the Arduino sketch folder
Download Stanford ArduPlane

29. Building
Open \Stanford_ArduPlane\ \Stanford_ArduPlane.ino with Arduino
Check the board type (Mega 2560) and COM port
“Verify” = compile
“Upload” = compile and upload to APM

30. The Code Editable: Not Editable: AA241X_ControlLaw.ino
AA241X_ControlLaw.h
Not Editable:
AA241X_Competition.h
AA241X_aux.ino
AA241X_aux.h
Everything Else…

31. The Code State and Control Variables (AA241X_aux.h)
Roll, pitch, yaw angles and rates
Inertial velocity and accelerations
Heading
Airspeed
GPS X-Y positions
GPS and Barometric Altitudes
Battery Consumption
RC Inputs, Servo + Throttle Outputs

32. The Control Loops AA241X_ControlLaw.ino
AA241X_AUTO_FastLoop(void){} ~50Hz
AA241X_AUTO_MediumLoop(void){} ~10 Hz
AA241X_AUTO_SlowLoop(void){} ~3.3 Hz
Distribute algorithm to use CPU cycles wisely
Beware of APM Memory limits
256k Flash Program Memory, 8K SRAM, 4K EEPROM

33. The Camera Function AA241X_aux.h
// Camera functions ///////////////////////// Function takeASnapShot()//// Example:// snapshot mySnapShot = takeASnapshot();//// mySnapShot.pictureTaken: range 0 or 1, indicates whether or not the picture was taken. 0 if not enough time between successive pictures, or if no GPS lock, or of energy cap reached, or out of altitude bounds// mySnapShot.timeOfPicture;// mySnapShot.personsInPicture: array of length 3 with values 0 or 1, indicating which persons were in the picture. personsInPicture[i] == 1 meanse person i was in the picture// mySnapShot.centerOfPictureX: X position of the center of the picture, in NED coordinates // mySnapShot.centerOfPictureY: Y position of the center of the picture, in NED coordinates// mySnapShot.diameterOfPicture: indicates the diameter of area covered by the picture // mySnapShot.centerOfPersonEstimateX[i]: X position in NED coordinates of the center of the circular area within which the i-th person is located. // mySnapShot.centerOfPersonEstimateY[i]: Y position in NED coordinates of the center of the circular area within which the i-th person is located.// mySnapShot.diameterOfPersonEstimate[i]: diameter of the circular area within which the i-th person is located.

34. Telemetry Plotting Two types of logs
Telemetry log
Dataflash log
store at higher log-rates
Download from APM over USB Cable
Mission Planner can dump matlab data files

35. Airframe Construction
The Problem
Fly Autonomously
Airframe Construction
State Estimation
Algorithm Processing
Control Actuation
Ground Monitoring

36. Resources FliteTest: youtube channel DIY Drones: forum
RC groups: forum
GrabCAD: community CAD models
3DRobotics: Store and Manuals
GitHub: Stanford_ArduPlane Code