Hi All,
We have a cube orange autopilot but due to the frame layout it is impossible for us to mount the autopilot in the center of mass of the drone.
This configuration generate bad oscillations when the drone brake after an high speed flight.
To solve this problem we tried to mount the autopilot outside of the frame but in the center of mass and it seems that the oscillations problem is solved.
As we can’t show at the client a drone with an autopilot mounted externally from the frame, we thought to add an external IMU to the system mounted in the center of mass inside the frame. In particular, we are trying to configure an VectorNav VN-100 rugged module as external IMU.
We have also an Here3+ GNSS/Compass.
As the VN-100 does not have a GPS module inside, to have a good AHRS estimation, we would like to use the EKF3 of the Arducopter reading the raw IMU values from VN-100 module.
Also we need to disable the internal (three) IMU’s of the cube orange (to prevent any form of oscillation) and use only the external IMU (VN-100) that the Arducopter see as “IMU0”.
To do that we setted the following parameter:
- [AHRS_EKF_TYPE] = 3 (ArduPilot’s EKF3)
- [EAHRS_TYPE]= 1 (VectorNAV)
- [EAHRS_OPTIONS] = 1
- [EAHRS_RATE] = 50 Hz
- [EAHRS_SENSORS] = 2 (Only IMU)
- [SERIAL1_BAUDRATE] = 115200
- [SERIAL1_PROTOCOL] = 36
- [ INS_ENABLE_MASK] = 1 (FirstIMU)
- [ EK3_PRIMARY] = 0 (FirstIMU)
After that all seems works fine before arming (when we tilt the drone we can see the correct and responsive response of the AHRS system) but when we try to arm (put the stick in the arming position) we have to wait more than 20 seconds to see the drone in arming state and when we takoff, we have a lot of delay from the command of yhe stick to see its effect on the attitude of the drone and the drone is uncontrollable.
Strangely, if we restore the use of the internal IMUs (cube orange) and disable the use of the external IMU (VN-100), all works fine.
I hope the explanation is clear.
The last strange thing is that when we disconnect the GCS from the autopilot and retry to reconnect to it, we are no longer able to connect with it (neighter with radio telemetry nor with usb cable straight to cube orange micro usb port.
Could someone help us ?
Thanks in advance for your time and effort.