I never thought building an altitude hold system with a sonar would be this hard… I wanted to build the “simple” sonar altitude hold to be able to test the “hard” IR scanner better. I ended up crashing the unit 10 times and found out that I need a much better setup to achieve this.
Problems:
1- High speed air out of the nozzle is impacting the sonar performance.
2- I believe the grass as a sound reflector is not doing a good job because the sonar is utterly inconsistent in reaction. AND this is a relatively expensive sonar at $30.
3- The codes I came up with are not even close to do the job. The code has to incorporate approach speed and a fully automated throttle control. I will re-visit this in the future, and maybe implement a high precision BARO instead of the sonar for higher altitude hold and try another type of sensor for landing, because of sonar’s poor performance, probably due to nozzle air.
So, I decided to go ahead and test the IR scanner before totaling the unit. My concerns regarding the scanner making the unit unstable were proven wrong.
It worked perfectly
You can see it spin at the top of the unit for the first time, doing a great job. The unit clearly reacted to my hand and body and rushed the other direction when approached. The plan was to test it during GPS hold but the GPS hold was not stable. I probably damaged it during the last crash which was nasty. So I deactivated the GPS during this test.
https://www.youtube.com/watch?v=9VhlexQbljQ