Pathfinder Edge: Camera and IMU considerations
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For Pathfinder Edge to precieve the world. It needs an nader downwards facing camera and an imu in the same motion frame as the camera.
Camera
The pathfinder edge box will work will work with any camera/camera system that can meet the following requirements.
connects to a computer over USB using the UVC protocal
outputs a 1080p RGB image (1920x1080) at >= 60 FPS
~90deg FOV
enough dynamic range to not clip the majority highlights/shadows of the image in application
Fast enough sensor readouts to not have rolling shutter or image motion bluring artifacts at expected speeds
Recommended cameras
We have found that a UVC AR-0234 camera with a ND4 to ND16 netural density filter will work with the Pathfinder edge system. See below
AR-0234: https://www.amazon.com/SVPRO-Global-Shutter-USB-Camera/dp/B0CC28R5TL?th=1
ND filters: https://www.amazon.com/NEEWER-52mm-Lens-Filter-Kit/dp/B06XRY2HLD
It does not matter what USB-A port the camera is plugged into.
Gimbal/Camera orientation.
Pathfinder edge requires that the camera remain level during the flight. Our recommended solution is to use a 2 axis mechanical gimbal. the two axis should be aligned to drone roll and pitch. see below.
gimbal*: https://www.amazon.com/Camera-Stabilizer-Technology-Brushless-Quadcopter/dp/B0BW9LZHJ1 (assumes a 12 power)
gimbal power supply: https://www.pololu.com/product/5677
*to mount the recommended camera and nd filter to this gimbal aditional components are needed.
camera yaw
In addition the top of the camera image must be aligned with the front of the drone. This would be observed as when the drone is pointed north and has a yaw of 0, the top of the image would be north. left would be west, right would be east, and bottom would be south. We use the drone's compass over mavlink to determine our orientation
IMU
In addition to mechanical corrections, Pathfinder uses an IMU to for additional orientation corrections. This imu should be ridgid in position and orientation to the camera.
Currently we only support Hillcrest BNO080 and BNO085 IMUs for these corrections. see below:
IMU orientation
in camera frame the IMU should be oriented:
the positive x axis points at the top of the image
the positive y axis points at the left of the image
the positive z axis comes out of the image.
if the drone were level making the camera level, the IMU should be oriented:
the positive x axis points forwards
the positive y axis points left
the positive z axis points up
IMU position
The IMU does not need to have any positional offset to the camera though it should be mounted as close as possible to the camera to avoid acclerations due to rotations.
IMU wiring
The imu should be wired up in the same pinout as QWIIC. the 4 pin jst-sh connector should be wired as follows in reference to the data sheet page 2
https://www.jst-mfg.com/product/pdf/eng/eSH.pdf
ground
vcc/3.3v
SDA/data
SCL/clock
this jst-sh connector should be connected to the jst-sh port on the front of the box
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