Kyle Ikuma presented on his SPRE project involving the PX4 Vision Dev Kit and development of an environmental flow vector (EFV) sensor array. He designed hardware including a power distribution system, EFV sensor PCB, and 3D printed sensor mounting chassis. The sensor array was tested in a wind tunnel mounted on a custom fixture and flown on a drone. The presentation covered the project goals, hardware components, CAD designs, manufacturing challenges, and preliminary flight test results.

1. Final SPRE Presentation
Summer 2021
Kyle Ikuma (Advisor: Nate Simon)

2. Projects
PX4 Vision Dev Kit Setup/Testing
FlowDrone hardware design, PCB design for EFV
sensor integration

3. What is PX4 Vision?
The PX4 Vision Autonomy Development
Kit is a robust and inexpensive kit
for enabling computer vision
development on autonomous vehicles.
The kit contains a near-ready-to-fly
carbon-fiber quadcopter equipped with
a Pixhawk 4 flight controller, a UP
Core companion computer (4GB memory &
64GB eMMC), and a Occipital Structure
Core depth camera sensor.

4. Core Components
● Pixhawk 4 FC
● PMW3901 optical
flow sensor
● TOF Infrared
distance sensor
● Structure Core
depth camera
● UP Core computer
● Pixhawk4 GPS

5. ● Almost ready-to-fly drone
with vision hardware
installed
● Install and bind R/C
receiver, ensure companion
computer and flight
controller are set up
● Will perform test flight
on-campus
PX4 Vision Dev Kit

6. FlowDrone Hardware
Development

7. Subproject:
Power Distribution System

8. Power System
- Matek FCHUB-12S X-Class Power Distribution Board
- 12V/4A to sensor board
- 12V feeds into VReg to 10V
- 5V/5A to power RPi

9. JST-PH 2.0
power connector

10. Sensor Assembly/Mounting to X500 UAV
Custom top plate
Original X500 top plate
Sensor array
PX4 Flight Controller
GPS/Compass
Sensor Base PCB

11. 20mm standoffs
6mm standoffs
Custom Top Plate

12. Subproject:
EFV Sensor Array PCB Design
& Other Related Hardware Design

13. PCB Schematic; V1 (4 sensors mounted on chassis)
Connected by header pins:
Fastened in place by (TBD):
- interlocking mast edges (teeth)
- Rubber bands for tension
Not pictured: Mast version with doubled
hight (also ordered)
Mast Chassis

14. V1 Sensor Mounting
Female right angle header pins
Male header pins
Base PCB
Sensor Module

15. V1 Sensor Mounting
Future additions/design goals:
- Secure the sensors to the board
- Currently the header pins are the only
attachment points between the sensors and
the base
- Fasten sensors to each other to ensure alignment
- Longer PCBs may be subject to
deformation/vibration
- Header pins have some “wiggle room” -
mitigate this

16. V1 Sensor Assembly/Mounting
Custom CF top plate
Original X500 top plate
Sensor array
PX4 Flight Controller
GPS/Compass
Sensor Base PCB

18. Full CAD Assembly
- Layout of sensors, boards, components, etc. to prevent
any interference in assembly
- Simulation
- Further down the line:
- Add densities/weights to corresponding parts
- Mass/inertial properties, possibly output to .urdf
files for ROS simulation
- CFD/Flow simulation around propellers &
sensors

19. CAD Sensor Mounting (Version 2)
Design changes:
- Corrected errors with previous board
- Mirrored sensor pattern across vert. axis
- Added gain resistor mounting holes to AD623
op-amp
- Added hole in PCB for sensor
- Interlocking mechanism
- aligns sensors with each other, increases
rigidity
- Proposed securing mechanism (next slide)
- Low-pressure “cavity” due to four walls may cause
unexpected aerodynamic issues

20. Securing the sensors to the board:
- Proposed solution: square “clamp” attachment
- “overengineered” -Hultmark, 2021
- Probably will end up using rubber bands or other janky solution

21. Manufacturing the EFV Sensor Slot in DipTrace
- Test the manufacturing capabilities of OSH Park
- Test 1: NC drill file; specify 4x 0.6mm holes
- Holes over the real sensor location
- Test 2: rectangular board outline cutout
- Placed on separate location on board away from all other
components
- Will there be differences? Which one is more reliable?
- Inner radius of the (presumably) milled board outline?
- Results:
- 4x hole looked like a single drill point; presumably because drill bit
did not have any board material to catch onto past the first hole
- Rectangular hole was not manufactured at all
- For all V2 sensors, Nate used a drill press & widened the holes

22. Wind Tunnel Mounting
2DoF adjustment
(pitch, yaw)
Attaches to bottom of
wind tunnel
Sensor array

23. Test Fixture in J-wing Wind Tunnel

24. ● Designed in EAGLE
○ Can specify milled slot (teal)
○ OSH Park has documentation and
support on its website on how to specify
slots/other PCB features in EAGLE
○ Fusion 360 integration/link: changing
EAGLE project will update 3D design in
Fusion
○ Overall good decision to switch over
● Only ‘half’ tab and pocket towards the
bottom of the board
● Top part of mast separated to prevent
any weird “cavity” effects of V2, if any
PCB V3 + Chassis

25. PCB V3
● Issue: sensors measure magnitude of flow; no way to
know the direction of flow through sensor
● Flow from backside of PCB on the opposite sensors
as wind direction might cause issues in calculating
wind direction
● Proposal: X-brace
○ How can we prevent airflow passing between/through
sensors from reading through the wrong/unintended
sensors?
○ Dual purpose: stabilizes PCBs against each other and
should provide a guarantee on wind direction
calculations, since the only sensors reading any wind
velocity would be those facing the wind
○ “Compartmentalizes” airflow between sensors,
prevents airflow from perturbing other sensors in the
array

26. PCB V3

27. Chassis V2
● New chassis:
○ 4 mounting holes for stability
○ Sensor array shifted to center of chassis board
○ Changed custom top plate and wind tunnel test fixture to
reflect changes in mounting hole pattern
○ To do: common ground between I2
C and power source
● 3D printed carrying case
○ Keeps dust/particles off sensing elements
○ Prevents PCBs from moving around too much

28. Hardware Test
● Circuit successfully reading EFV voltages into
Raspberry Pi, sensitive to wind
● Tower is quite sturdy (filed edges interlock)
● 1 working EFV (challenges with sterile storage /
transportation of the sensors)
● SEAS Magazine interview + flight photos

29. Flight Test
Sensor on
Props on
Takeoff
Forward -> Backward
Forward -> Backward
Hovering Landing
Props Off
Hovering

30. Questions/Comments