LibrePilot Forum

Users => Vehicles - MultiRotors => Topic started by: Saga40 on July 21, 2017, 04:58:02 am

Title: CC3d external gps for Position Hold
Post by: Saga40 on July 21, 2017, 04:58:02 am

Is it possible? I have a CC3D controller (not revo). I have also bought and setup an external gps device (NEO 7n). The gps is working properly. But I am wondering how to set up the position hold function, because right now, The system says there is a config error.

Title: Re: CC3d external gps for Position Hold
Post by: Mateusz on July 21, 2017, 06:29:20 am

Unfortunately that is not possible

• GPS is only one of sensors that just help to maintainin position, all sensors are required and GPS itself has the poorest accuracy and precision (+- 4m error). These additional sensors like magnetometer and barometer measure also different physical  properties which other sensors can't, so they cannot be compensated by anything.
• You would need to run sensor fusion algorithm INS13 (which is extended kalman filter implemented for navigation) CC3D has too little RAM to run it, so it's not available, also no need because of sensors missing.

GPS can be used though on CC3D to tell you the approximate position, if you lose the quad, but definitely not position hold on a racing flight-controller.
I am not sure though if GPS position is worth extra weight on racing quad, given 10-20Hz updates these GPS-s usually deliver and the speed of quads.

Title: Re: CC3d external gps for Position Hold
Post by: Saga40 on July 21, 2017, 07:42:30 am

Thats disappointing. So would I need to buy a new controller in order to use the position hold function? or additional sensors?

Title: Re: CC3d external gps for Position Hold
Post by: TheOtherCliff on July 21, 2017, 08:00:50 am

A new controller.  Revo (any of 3 styles that have all sensors), Nano, or Sparky2.  Most are around $40-$50

Title: Re: CC3d external gps for Position Hold
Post by: Saga40 on July 21, 2017, 08:14:15 am

Ok so something like this should do it?
https://hobbyking.com/en_us/openpilot-cc3d-revolution-revo-32bit-flight-controller-w-integrated-433mhz-oplink.html (https://hobbyking.com/en_us/openpilot-cc3d-revolution-revo-32bit-flight-controller-w-integrated-433mhz-oplink.html)

Title: Re: CC3d external gps for Position Hold
Post by: Mateusz on July 21, 2017, 10:31:25 am

Yes, you also need second external Magnetometer, most often found in GPS modules. Internal mag will only be used for aligning external Magnetometer. You also need to calibrate all sensors, make sure they are functioning properly baro covered from light and wind etc... You also need to tune PIDs so it does fly great just with Complementary (gyro+accel only). If you have problems with basic setup adding more complexity like position hold won't solve them. It's pretty complicated feature which performance depends on many factors and is not easy to setup without learning a bit and reading wiki/forum.

Title: Re: CC3d external gps for Position Hold
Post by: Mateusz on July 21, 2017, 10:42:15 am

Can you post your GPS board picture ? Bottom and top ? Maybe we can see if it has magnetometer. You would need to mount it on a mast ~12cm usually that is not rotating so has at least two mounting screws. If you need more help just ask.

Title: Re: CC3d external gps for Position Hold
Post by: TheOtherCliff on July 21, 2017, 05:03:55 pm

That HobbyKing Revo should work fine, but HobbyKing sticks you pretty big with shipping charges ($57 total cost last time I checked).  Banggood sells the same one for $47 shipped.  Here is a link to a mini-review page with links to buy and issues found for several types of Revo/Nano/Sparky2/CC3D.

https://forum.librepilot.org/index.php?topic=3562.0