We're interested in developing a "next generation" optical flow sensor where the camera lens is slaved to a high accuracy laser altimeter in order to provide dynamic focus and increase the useable range. We're looking for someone to flight test our new SF11 laser altimeter with the PX4Flow so that we can collect some real world data before moving forward with the final design. @Fabien, would you be interested in testing the SF11 on your project? We already have some high altitude flight data but we need verification of the short range performance as well :).
Thanks, going to give that a try next time. Currently we're still hampered a bit due to the Lidar Lite jumping to 12m occasionally, we moved it to its own BEC, but now it just up and quits sometimes.
I've ordered some stuff (Traco TSR 1-2450) for a dedicated power supply, according to Pulsedlight the stability of the 5V is critical.
It's hard to tell from such a short flight, but it looks like the quad may be drifting on X-Y axes. I had this problem (my Loiter using OF was drifting back and forth) and was able to significantly improve it by going into Mission Planner and adjusting upward the Loiter-P value. This made the response to drifting in X-Y much more aggressive. If you crank it up too high though, the quad will start "jitter" in place when loitering.
Also, I think it's recommended to have a decent amount of variation on the surface the camera is looking at. I can't tell, but that grey carpet might be too uniform. Maybe put down painter's tape or something that won't blow around?
I see that the solution to get OF working lies in setting EKF_GPS_TYPE -> 3
But this sets the EKF to not use the GPS. Can you then still automatically fly GPS waypoints?
Does the NKF support fusing both?
Cheers,
Jon
Goro Senzai > Jon VerbekeNovember 25, 2015 at 6:03am
Hi Jon,
I'm not an expert on this, but by looking at the EKF source code, it looks like GPS won't be used at all when you set EKF_GPS_TYPE to 3. However, when you fly in GPS mode and if you lose GPS signal, and if OF data is available, it looks like the software will fall back to using OF (AP_NavEKF_core.cpp around line 500).
I haven't looked at EKF2 code, so I have no idea about that.
In any case, I hope someone who knows what they are talking about could confirm/correct me.
Replies
Hi Fabien,
We are working on a somewhat similar project, but at a higher altitude. Let me know if I can shoot you a PM sometime. :)
-Thomas (IR-LOCK)
We're interested in developing a "next generation" optical flow sensor where the camera lens is slaved to a high accuracy laser altimeter in order to provide dynamic focus and increase the useable range. We're looking for someone to flight test our new SF11 laser altimeter with the PX4Flow so that we can collect some real world data before moving forward with the final design. @Fabien, would you be interested in testing the SF11 on your project? We already have some high altitude flight data but we need verification of the short range performance as well :).
We've still got some room on the quad, so that sounds good. Then we can compare it with both sonar and the lite.
I'll contact you via PM to explain our project a bit more.
Thanks, going to give that a try next time. Currently we're still hampered a bit due to the Lidar Lite jumping to 12m occasionally, we moved it to its own BEC, but now it just up and quits sometimes.
I've ordered some stuff (Traco TSR 1-2450) for a dedicated power supply, according to Pulsedlight the stability of the 5V is critical.
Can you set RNGFND_MAX_CM to 1100 to ignore Lidar Lite readings above 11 meters?
Very nice that there is a thread for the PX4Flow, and thanks to all the developers for their hard work.
Below is a video where we take off to 1.5m, turn 180 degree, then command a 1m move via Dronekit. After reaching 1m, it lands.
https://youtu.be/HK8bbefFjCQ
The takeoff could use some work, I think we'll try using EKF2 and setting RNG_GNDCLEAR and RNG_OFFSET next.
Would I be correct in assuming that if we had about 20cm legs, the takeoff could be performed fully under optical flow?
It's hard to tell from such a short flight, but it looks like the quad may be drifting on X-Y axes. I had this problem (my Loiter using OF was drifting back and forth) and was able to significantly improve it by going into Mission Planner and adjusting upward the Loiter-P value. This made the response to drifting in X-Y much more aggressive. If you crank it up too high though, the quad will start "jitter" in place when loitering.
Also, I think it's recommended to have a decent amount of variation on the surface the camera is looking at. I can't tell, but that grey carpet might be too uniform. Maybe put down painter's tape or something that won't blow around?
Thank you Paul for posting very useful information!
I'll switch to master and give EKF2 a try later and report back.
Hi,
Can you use both OF and GPS?
I see that the solution to get OF working lies in setting EKF_GPS_TYPE -> 3
But this sets the EKF to not use the GPS. Can you then still automatically fly GPS waypoints?
Does the NKF support fusing both?
Cheers,
Jon
Hi Jon,
I'm not an expert on this, but by looking at the EKF source code, it looks like GPS won't be used at all when you set EKF_GPS_TYPE to 3. However, when you fly in GPS mode and if you lose GPS signal, and if OF data is available, it looks like the software will fall back to using OF (AP_NavEKF_core.cpp around line 500).
I haven't looked at EKF2 code, so I have no idea about that.
In any case, I hope someone who knows what they are talking about could confirm/correct me.
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