Is Optical Flow Sensor useful for a fixed-wing?


I’m new to Ardupilot/Arduplane and I’m currently building my first project using it. This is a fixed-wing (a Binary 1200mm from SonicModell) with a Matek H743-Wing FC with Arduplane 4.1.

I started to read the Arduplane documentation a couple weeks ago and I’m planning to read it entirely. (Thank you to those maintaining documentation).

My goal is to setup the plane so that it take-off and land automatically. I bought GPS/Compass as well as air speed sensors. I also bought an Optical Flow/Lidar sensor (Matek Optical FLow & Lidar Sensor 3901-L0X).

Here is my question: Is the Optical FLow sensor can be useful for a fixed wing? Should I disable it and keep only the Lidar sensor enabled? I think that the Lidar could help the plane to flare when landing however I’m wondering what the optical flow could do since I have an air-speed sensor.

Information I found about optical flow was mostly used with drones. I’m wondering if there is a benefit to use it with a fixed-wing.

Thank you for your time.

Guylain Plante

I don’t think so. Copter uses optical flow to help maintain a fixed position. I’m not sure what it would do for Plane but probably nothing. The Lidar will help for landing by giving precise altitude information, however the Matek unit you have will not be of much value. It’s range is less than 2m, realistically closer to 1.5m. (I have one in a multi rotor build) Unless your approach is really flat, by the time the plane is at 2m it would be too late for this range finder to make any significant difference.

There is more value in getting the airspeed sensor set up correctly.

Thank you for your reply.

I will probably disable the optical flow and keep the lidar only.
You are right about the Matek lidar, it works only for about 1.5 meter. I also ordered another lidar (Benewaki tfmini) that will work with higher range. I saw somewhere that I could enable both lidars and use one for shorter distance and the other for higher distance. I will look back at the documentation about this.

Thanks again for your time.

There are some advantages. The flow can act as a very accurate range finder when used in conjunction with GPS, and assist with speed readings (does not replace a proper airspeed sensor). Sorry I don’t have more info as I read it on the cubepilot FB group some time ago.

Interesting. Is the optical flow more accurate than the Lidar range finder for altitude?

My concern about the speed is that it would be reporting ground speed, not air speed. As you pointed out, it’s not a replacement for a proper airspeed sensor.

I don’t think it’s more accurate than a lidar. That said it’s way smaller and cheaper (then longer range lidar like the LW20), so good for some builds. Philip Rowse of cubepilot was the one talking about it. Message him for more info.

The range on the flow is pretty useless outside. Just use the TFmini.