@arifg wrote:
Hi there,
I have problems using Lidar on my copter. This is SF 11/C from Lightware. I already wrote here about the issue I had during auto-mission flight when I crashed the vehicle but unfortunately that topic remained unanswered. Yesterday I was able to reproduce the issue in safe environment. So I have both TERRAIN_ENABLE=1 and TERRAIN_FOLLOW=1 and I made a test using RTL using my copter. I had the theory that the problem occurs when Lidar misses the ground and I was able to prove it during my test flight. Normally the Lidar range is 120 m but to perform a test I suppressed the sensor by obscuring its lenses with transparent sticky tape so its effective range reduced to about 40 meters. I climbed the copter to 40 meters up in Position Hold mode and hit RTL. And the issue occurred right away: instead of returning home the vehicle started to climb and at the same time I noticed the reported altitude on my OSD dropped to zero and at some point became negative! This is recorded in the attached log. At some point I arrested the climb (it seemingly was going to climb indefinitely) and landed it manually in Stabilized mode (vehicle didn't stop to climb in Position Hold mode) to analyse the log. I attached the picture with this exact moment: in this snippet red is Lidar altitude - it goes to 130 meters which is above RNGFND_MAX_CM=12000 and means that Lidar is nonfunctional. As described in http://ardupilot.org/copter/docs/terrain-following.html in this case the autopilot should switch to Baro altimeter and consider Home Altitude as a reference point instead of terrain elevation but that was not what I see in the log. Instead there is a strange altitude source (accelerometers?) - green line showing kinda weird data around a zero at some point dropping way below zero. Blue line is barometric altitude. Could anyone explain me the data and what can I do to instruct the autopilot to use barometer in this case or at least GPS altitude?
Thank you in advance!
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