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Always failing to arm "need 3D Fix"


(Hugo Sardinha) #1

Hi everyone,

I started working with ardupilot on a fresh install of ubuntu 16,04 LTS and continuously am unable to arm. For now I just focusing on simulation
When I run:

sim_vehicle.py -v ArduCopter

and then try to arm throttle, I repeatedly get the message

APM: PreArm: Need 3D Fix
Got MAVLink msg: COMMAND_ACK {command : 400, result : 4}

I already set the param ARMING_CHECK to 0 but to no avail…

any ideas?


(Mike Boland) #2

What flight mode are you in?

This usually happens if you are in Pos Hold or Loiter and try to arm without a 3D Fix.


(Hugo Sardinha) #3

Hi @mboland

Thnks for taking time on this, I’m in guided mode…


(Mike Boland) #4

Guided mode, as far as I am aware, requires a GPS data stream.

What GPS input do you have?

Does it work in just stabilise mode?


(Hugo Sardinha) #5

Well, But I just want to work in simulation… where exactly is GPS stream meant to come from??
This is really weird, because on another machine with also a fresh ubuntu install I am able to change mode, arm and take off… the issue is that I am away from that machine and can’t check if there are any differences… there must be…

Actually on stabilize mode I am able to arm, but take off doesn’t happen… but in stabilize mode I guess that’s expected

Thanks again,
Hugo


(Hugo Sardinha) #6

I think I’ve figured out what the problem was…

I have to wait for the following messages to appear:

APM: EKF2 IMU0 is using GPS
APM: EKF2 IMU1 is using GPS

After this I’m always able to arm and take off. I am having another issue now which is when I take off
the and give the alt command at some point that value stops changing and copter continues to go up, but I’ll open a different thread for that. Thanks


(Amogh Bhagwat) #7

Hey @Hugo,
I am facing the same issue of unable to arm in LOITER mode.

I am not getting the mentioned messages.

I was following the instructions mentioned in Erle Robotics Simulation documentation for installation and execution.

Thanks.