Companion computer to fly in guided mode without GPS

YoniShpund · December 10, 2020, 10:07am

Hi all,

I am developing a companion software that takes control of a drone while it is flying.
I want to navigate the drone in guided mode (with NED coordinates) without any consideration of GPS.

Is there any way to use NED coordinates in a guided no GPS mode?

Hope you can help me with that.
Thanks,
Yoni

amilcarlucas · December 10, 2020, 10:12am

You need to add https://github.com/ArduPilot/ardupilot/pull/15854 on top of master, recompile the code and upload to the vehicle

YoniShpund · December 10, 2020, 10:52am

Can you please explain how I can control a drone in auto mode?

amilcarlucas · December 10, 2020, 11:12am

My bad, for real time control using a companion computer you do need “guided no GPS” mode.

You can start here: Indoor Flying Guidelines — Copter documentation

continue here:

and here:

github.com/ArduPilot/ardupilot

AP_NavEKF3: add source selection to allow switching between GPS and T265

ArduPilot:master ← rmackay9:ekf-pos-source2

opened 06:14AM - 13 Jul 20 UTC

rmackay9

+1501 -153

This PR adds support for manually switching the EKF3 between sensors sources use…d for position, velocity and yaw. It also includes a lua script to automatically switch between GPS and NonGPS sources. - New AP_NavEKF_Source class is relatively simple with 10 new parameters that allow the user to set to sources (primary and secondary) for position (_POSXY, POSXY**2**, POSZ, POSZ**2**), velocity (_VELXY, _VELXY**2**, _VELZ, _VELZ**2**) and yaw (_YAW, _YAW2). This class allows the currently active source for each axis to be get or set using methods like getPosXYSource(). - RC_Channel option "89" allows the user to change all active sources between the primary and secondary - EKF3 is enhanced to check the active source when deciding what sensor data to fuse. It also checks for a change in source and performs a reset. This PR also includes a couple of additional, mostly unrelated fixes: - EKF3's ExtNav support enhanced to allow using non-ExtNav altitude (i.e. baro, rangefinder, etc) - VisualOdometry T265 driver ignores sensor input for 1 second after a reset (in testing we've found dozens of resets happen one after the other) - AHRS's PreArm check method is made consistent with other subsystems This has been tested in SITL and on a real vehicle. I've put the logs for two tests below: - [garden test](https://www.dropbox.com/s/2vecfiorwae2j8y/garden-test-13July2020.bin?dl=0) - [hotel test](https://www.dropbox.com/s/10o54ro7d88okna/hotel-test-13July2020.bin?dl=0) To test using GPS + Vicon in SITL the following parameters should be set: - AHRS_EKF_TYPE = 3 - EK2_ENABLE = 0 - EK3_ENABLE = 1 - EK3_SRC1_POSXY = 3 (GPS) - EK3_SRC2_POSXY = 6 (External Nav) - EK3_SRC1_POSZ = 1 (Baro) - EK3_SRC2_POSZ = 6 (External Nav) - EK3_SRC1_VELXY = 3 (GPS) - EK3_SRC2_VELXY = 6 (External Nav) - EK3_SRC1_VELZ = 3 (GPS) - EK3_SRC2_VELZ = 6 (External Nav) - EKF3_SRC1_YAW = 1 (Compass) - EK3_SRC2_YAW = 2 (External) - VISO_TYPE = 1 - SERIAL5_PROTOCOL = 2 (MAVLink) - RC9_OPTION = 90 (EKF Pos Source) Then start SITL from the ArduCopter directory with this command - ../Tools/autotest/sim_vehicle.py --map --console -A "--uartF=sim:vicon:" To switch between sources: - rc 9 1000 (switches to GPS) - rc 9 1500 (switches to vicon) To add offsets in position and orientation to the SITL vehicle: - param set SIM_VICON_YAW 45 (to rotate the Vicon system by 45 degrees) - param set SIM_VICON_GLIT_Y 50 (to add 50m of offset in the Y axis to the Vicon system) These are the known issues and questions: - PreArm check is perhaps too strict because it checks the EK3_SRC_xxx**2** parameters which many users may not use - The fall back from GPS->Optical Flow doesn't work anymore but in practice I don't think it worked before either. - Source changes of Z-axis velocity alone will not trigger a velocity reset. This is mostly because of existing limitations in the EKF. - When the Yaw source changes to the compass, the vehicle's yaw takes 1 to 2 seconds to rotate around to the correct heading. I'm unsure why it is so slow because resets to ExtNav yaw occur immediately This is the additional testing we should do before merging: - Yaw resets from all possible sources (Compass, GSF, ExtNav) All feedback is greatly appreciated!

YoniShpund · December 10, 2020, 11:58am

Thanks for replying. This looks interesting but I am looking for a solution without a camera.

Do you know about any solution that might help me?
I need to navigate the drone with NED coordinates without consideration of GPS and without any additional tools (using only MAVLink)

amilcarlucas · December 10, 2020, 12:02pm

You will need some sort of GPS replacement: beacon or optical flow otherwise it won’t work.

amilcarlucas · December 10, 2020, 12:08pm

You could use stabilize flight mode a give joystick commands. But that is a huge hack!!!

Henrik · December 11, 2020, 12:13pm

As @amilcarlucas says, you need some other sensor to estimate the position of the drone. Without GNSS or any replacement can’t the drone know its position. You can find some replacements here: https://ardupilot.org/copter/docs/common-non-gps-navigation-landing-page.html. I think optical flow is the easiest if you are flying indoors, but that will also have some drift.

There does exist a Guided NoGPS mode, but then you can’t send NED coordinates, only attitude targets.

YoniShpund · December 13, 2020, 10:18am

Thanks a lot for replying.

In Guided NoGPS mode, is there a way to know the speed of the drone?

Henrik · December 26, 2020, 6:14pm

No, there is not. You need some suited sensor to be able to measure the speed, e.g. those mentioned in my previous answer. GNSS is the most common, but if you are indoors I think optical flow is the easiest.

You could theoretically try to estimate the speed from the IMU readings or try to simulate the movements from the propeller thrusts in a dead reckoning scheme, but that will be prone to drift and difficult to implement. It is more normal to consider speed unobservable without more sensors.

junaid313 · June 14, 2023, 8:05pm

if you need help with this I can help you.

Thasindu_Wickrama · August 12, 2024, 7:43am

Hi, im also having an issue with the optical flow sensor combined with pixhawk on ardupilot firmware, since guided no gps is not available on px4, once the communication is established through UDP, uav doesnt respond to any commands, im using dronekit for script based controlling.