PX4 with AirSim -> Preflight Fail: High Accelerometer Bias

[mych907]

Hi, I'm a beginner to both AirSim and PX4.

I'm running a px4 sitl in windows 10 cygwin.
(cygwin version 0.8, px4 1.10.1, Unreal Engine 4.25.4)

I ran the python code below to move the multirotor to a position 5 meters high from ground.
It works for the first time, although not 100% sure if it actually is at the exact 5 m.

The problem is, when I run the exact same code one more time, it gives me a warning.

"WARN [commander] Preflight Fail: High Accelerometer Bias"

Below is the code.

import airsim

client = airsim.MultirotorClient()
client.confirmConnection()
client.enableApiControl(True)
client.armDisarm(True)

airsim.wait_key('Press any key to takeoff to 5m')
client.takeoffAsync().join()

client.moveToPositionAsync(0, 0, -5, 5).join()

airsim.wait_key('Press any key to reset to original state')

client.landAsync().join()

client.armDisarm(False)
client.reset()

client.enableApiControl(False)

Below is the warning message (third line from the bottom)

ASCL-321@DESKTOP-VT4BNV5 ~/PX4/Firmware
$ make px4_sitl_default none_iris
[0/1] cd /cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_...e /cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_default             SITL ARGS
sitl_bin: /cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_default/bin/px4.exe
debugger: none
program: none
model: iris
src_path: /cygdrive/c/PX4/home/PX4/Firmware
build_path: /cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_default
SITL COMMAND: "/cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_default/bin/px4.exe" "/cygdrive/c/PX4/home/PX4/Firmware"/ROMFS/px4fmu_common -s etc/init.d-posix/rcS -t "/cygdrive/c/PX4/home/PX4/Firmware"/test_data
INFO  [px4] Creating symlink /cygdrive/c/PX4/home/PX4/Firmware/ROMFS/px4fmu_common -> /cygdrive/c/PX4/home/PX4/Firmware/build/px4_sitl_default/tmp/rootfs/etc
______  __   __    ___
| ___ \ \ \ / /   /   |
| |_/ /  \ V /   / /| |
|  __/   /   \  / /_| |
| |     / /^\ \ \___  |
\_|     \/   \/     |_/                                                                                                                                                                                                                                                 px4 starting.
INFO  [px4] Calling startup script: /bin/sh etc/init.d-posix/rcS 0
INFO  [dataman] Unknown restart, data manager file './dataman' size is 11798680 bytes
INFO  [simulator] Waiting for simulator to connect on TCP port 4560
INFO  [init] Mixer: etc/mixers/quad_w.main.mix on /dev/pwm_output0
INFO  [mavlink] mode: Normal, data rate: 4000000 B/s on udp port 14570 remote port 14550
INFO  [mavlink] mode: Onboard, data rate: 4000000 B/s on udp port 14580 remote port 14540
INFO  [logger] logger started (mode=all)
INFO  [logger] Start file log (type: full)
INFO  [logger] Opened full log file: ./log/2021-03-16/12_33_43.ulg
INFO  [mavlink] MAVLink only on localhost (set param MAV_BROADCAST = 1 to enable network)
INFO  [px4] Startup script returned successfully
pxh> INFO  [simulator] Simulator connected on TCP port 4560.
INFO  [mavlink] partner IP: 127.0.0.1
INFO  [ecl/EKF] EKF aligned, (pressure height, IMU buf: 22, OBS buf: 14)
INFO  [ecl/EKF] 3669152: EKF GPS checks passed (WGS-84 origin set)
INFO  [ecl/EKF] 8211913: EKF commencing GPS fusion
INFO  [commander] Takeoff detected
INFO  [commander] Landing at current position
INFO  [commander] Landing detected
INFO  [logger] closed logfile, bytes written: 1587329
WARN  [commander] Preflight Fail: High Accelerometer Bias
ERROR [sensors] Accel #3236 ERROR [sensors] Sensor Accel #0 failed. Reconfiguring sensor priorities.
WARN  [sensors] Remaining sensors after failover event 0: Accel #0 priority: 1

I see the same message on my AirSim screen too.

After this, it no longer flies. Why am I seeing this? Has anyone experienced and fixed this issue?

[mych907]

Forgot to include my settings.json file.

{
  "SeeDocsAt": "https://github.com/Microsoft/AirSim/blob/master/docs/settings.md",
  "SettingsVersion": 1.2,
  "SimMode": "Multirotor",
  "Vehicles": {
    "PX4": {
      "VehicleType": "PX4Multirotor",
      "UseSerial": false,
      "UseTcp": true,
      "TcpPort": 4560,
      "ControlPort": 14580
    }
  },

  "OriginGeopoint": {
    "Latitude": 37.776580,
    "Longitude": -122.309579,
    "Altitude": 0
  }
}

[mych907]

Nothing's been changed, but for some reason, it no longer shows the warning message. Problem solved.

[ahmed-elsaharti]

Hi @mych907, it does make sense that one (and/or all) of the sensors would freak out (on PX4's side) when you run client.reset()since (from what I understand) the autopilot is not expecting the drone to suddenly teleport to a new location instantaneously (realistically this would never happen irl). This probably results in PX4 translating that into a 'bad bunch of sensor readings'.

I could be completely wrong though but this is what popped into mind the first time I saw abnormal behavior when trying to reset the simulation in PX4 SITL/HITL mode. If you need to restart the simulation you would need to restart the PX4 stack along with the AirSim simulator (or atleast thats what I end up doing).

[mych907]

You are totally right! I must have commented out reset() at some point... Thank you so much, Ahmed!