PX4

What is the purpose of optical flow?

• • camera modules that use ground texture and visible features to determine aircraft ground velocity

  • By having accurate velocity, it can positive better and fly smoother.

Understand the specs in PX4FLOW (Visit https://pixhawk.org/modules/px4flow to see the specs of PX4)

• • 168 MHz Cortex M4F CPU (128 + 64 KB RAM)

    • • Cortex M4F CPU is a processor for the board

  • MT9V034 machine vision CMOS sensor with global shutter

    • • MT9V034 is a name for sensor to add into camera to enhance range

        • • Global Shutter: is the technical term referring to sensors that scan the entire area of the image simultaneously. This is very popular.

  • Optical flow processing at 4×4 binned image at 400 Hz

    • • 4x4 binned image is a way of grouping pixel together to reduce any loss of resolution

        • • Last paragraph of this article: http://www.starrywonders.com/binning.html

  • Onboard 16bit gyroscope up to 2000°/s and 780 Hz update rate, default high precision-mode at 500°/s

    • • Gyroscope is to measure angular rate (circular speed)

        • • http://www5.epsondevice.com/en/information/technical_info/gyro/

  • Onboard sonar input and mount for Maxbotix sonar sensors. (HRLV-EZ4 recommended, SparkFun Product Link)

    • • Sonar sensor is used to measure distance between the device to things around using sound wave

        • • http://education.rec.ri.cmu.edu/content/electronics/boe/ultrasonic_sensor/1.html

To access PX4, we use QGroundControl.

First, calibrating the pixhawk and px4 by connecting the two into a computer one by one using USB cable.

Once both are calibrated, connect them via I2C holes.

If the two are connected properly, the OPTICAL_FLOW_RAD should show strong signals, like the image below.

If the two are not connected properly, there should be no signal.