Discussions

I've been struggling trying to get reliable altitude data for my quad.  Whenever I try altitude hold, it'll continually rise or fall, but not hold any sort of steady altitude.  In testing I've let it get to the point where it landed and where it rose over 50ft after engaging altitude hold.  Here's my config:

Standard 3DR Quad kit with electronics (APM1 w/oilpan)

MB1200 XL Sonar with power supply filter installed per wiki

3DR Sonar Mount

900MHz Telemetry Kit

Turnigy 9X TX/RX

5000mAh LiPo

I'm using the BEC from one of the ESCs for my APM power.  My sonar values seem very accurate when I move the quad around myself without the motors running.  When the motors are running the sonar data becomes very erratic. 

Here's a pic of the tuning graph when I'm moving the quad up and back down without the motors running:

nomotors.jpg

Here's a pic of the same graph when the quad lifts itself to the same altitude:

motors.jpg

It seems like the value is almost stuck around 0.4 with the motors running.  The spikes you see are the correct alitude, but most of the time it's stuck at 0.4.

Any ideas on how to get alt hold working?  I have a pretty stock quad, so I'm hoping someone else has already figured a way around this problem.