Arming/disarming issues in assisted flight modes

PX4 Autopilot Configuration & Flight Modes ⚙️
1

Dear PX4 team,

I am using Pixhawk/PX4 for my quadcopter. Currently I am testing the ekf2 enabled firmware of the latest stable branch. Regarding this, I have a couple of questions:

  1. I realized, that arming and launching the copter is not possible in position control mode? I need to start the motors in stabilized mode and then switch to assisted mode (altitude or position control) afterwards. What is the reason for this? I would really like to use the copter in position control mode from the very beginning!
  2. When landing in assisted mode, I often have problems to stop/disarm the motors. Sometimes, I need to put the throttle low for a very long time, before the motors stop. It also happened a couple of times (especially in position control mode), that the copter almost flipped around on the ground? Could a badly configured/working landing detector be the reason?

Many thanks for your help!
Tom

2

This is currently not a supported way of operation. Either use Land/Start Modes or Start and Land in Stabilized mode. Landing in Position Control Mode may be dangerous especially when GPS Signal degrades and Flighcontroller assumes a Position Deviation while on Ground -> This causes Flipping (did in my case). AFAIK there will be changes to this in future Versions.

3

Hi Andreas,

first of all, thanks for your quick response!

Do you know when the changes are planned? Which release? And how do they look like or work? I know from DJI autopilots, that starting/landing with altitude hold and/or position control is no problem. I would love to see this also with the PX4 firmware. It simply should not try no level the copter and should not try to correct its position when the throttle stick is at the minimum position. Maybe this sounds easier than the problem really is, because it should only behave like this, when the UAV is on the ground. Couln’t you detect this, when the throttle is low, but there is no loss in altitude?

Many thanks for your support!
Tom

Kind regards,
Tom

4

@Andreas_Hoffmann, I just read this post and wanted to know if stabilized mode was still the only FM available, except automatic landing and RTL, of course. Because I had bad experience landing in Altitude mode, like description below. Thanks.

5

@chris66 there should be support for automatic Landing Detection and subsequent disarming of the Aircraft. Anyhow I did not yet Manage (or trust) to do it, and so I always land in Stabilized Mode.

6

@VertLim

1.Hi, Can you check you position state is whether valid. That is say, it is just when you home position and local position is valid, then you can switch to the position mode, but if you want to switch to altitude mode, it is just need the altitude is valid.

that arming and launching the copter is not possible in position control mode? I need to start the motors in stabilized mode and then switch to assisted mode (altitude or position control) afterwards.

  1. When you land, it will waste a long time to stop the motors, maybe the land detection is not very perfect. you can have a check your barometers, imu modules and the parameters of the controller PID.