Summary of Optical Flow Development in ArduPilot

Development Team
48

Hi Greg,

Thanks for sharing your experience. I can understand the difficulties you have gone through. Even I am on the same page.

Let me share my story:

My stack:

  1. Firmware installed - APM:Copter V3.5.0-rc6 (efab409b)
  2. PixFlow - Optical Flow
  3. Range Finder - Garmin Lidar Lite V3. Used PWM Connection.

I followed this guide step by step - http://ardupilot.org/copter/docs/common-px4flow-overview.html#pre-arm-checks

Test 1:

I tried the First Flight (Copter Only) as mentioned in the guide - I started flying the copter indoor in STABILIZE mode with EKF_GPS_TYPE = 0 at a height of 1 meter (approx). After a few minutes of flying, I switched to ALT_HOLD mode and my copter suddenly took an extreme hike in altitude and hit the ceiling and crashed, damaging the legs. Though it was not enabled to let ELF use Optical Flow, I am not able to figure out what went wrong.

Test 2:

I went to open space, set the EKF_GPS_TYPE parameter to 3 to make the EKF ignore GPS and use the flow sensor. Started flying in STABILIZE mode, took to copter to a height of 2 meters (approx), then switched to LOITER mode - Just in a nick of time, the poor copter dropped down damaging the legs, props and one motor. It didn’t get disarmed, I guess it just couldn’t respond to the throttle or something I don’t know.

Attached the logs for reference.
test1-stabilize-alt_hold-crash.bin (2.6 MB)
test2-stabilize-loiter-crash.bin.log (3.3 MB)

I am expecting to find the reason for these behavior before I do any further experiment with my copter.

My today’s goal was to test Position Hold using Optical flow and Lidar Lite V3 in LOITER & ALT_HOLD mode. But my ultimate goal is to make this thing work in GUIDED & GUIDED_NO_GPS mode. I want my copter to hold position even if GPS is not available for which I thought I could use Optical flow. So after this, i need to figure out - How to make this work in GUIDED mode.

Thanks.