Software setup

Autopilot focused setup guide

To access autopilot parameters, use AMC's Advanced Mode

Dragon SR autopilot comes pre-configured with MAVLink mode set to Low Bandwidth , which is the recommended setting for long-range, low-bandwidth data links. Side effects of that configuration is that the loading of parameters in AMC takes significant amount of time (also when connected over USB). If used data link allows for higher data throughput, the MAV_S_MODE can be set to Onboard Low Bandwidth .

Airframe presets

The autopilot comes with generic 10" quadrotor-X airframe parameters applied. The generic airframe ID (SYS_AUTOSTART) of the generic airframe is 1300001 and it includes following parameters:

• Control allocation and outputs mapping:

  • Symmetrical X-shaped quadrotor layout,

  • DSHOT as ESC porotocol with DSHOT_MIN set to 8%.

• Battery presets for 6S Li-Ion battery.

• ESC internal current sensing configured with scaling of 45 A/V.

• Commander presets (flight modes Stabilized/Altitude/MC Follow and arming without GPS).

• EKF2 tuning parameters.

• Rate, Attitude and Position controllers tuning parameters.

• Airmode enabled for Pitch/Roll/Yaw

• RC protocol set to CRSF and mapped to Skynode S RC_IN EXTRAS 1 port.

• UXRCE DDS client configuration.

• MAVLink low bandwidth mode enabled.

• IMU filters cutoffs values optimized for MC-Follow mode.

• Safety: Disabled arming by stick gesture (refer to Arming for more details).

• Security: Don't disclose GPS position in logs.

Sensors calibration

Having all the hardware components in place, perform required sensor calibration. Refer to Sensors Setup for more information.

Battery configuration

Configure the battery and current sensor parameters:

• BAT1_N_CELLS - number of battery cells connected in series

• BAT1_V_EMPTY - empty cell voltage - should be configured according to battery chemistry and battery manufacturer recommendation. Example values for different battery chemistry types:

  • Li-Po : 3.5V

  • Li-Ion : 3.0V

  • Li-HV : 3.5V

• BAT1_A_PER_V - current sensor amps per volt scaling value - set according to current sensor (typically ESC) manufacturer.

IMU filters configuration

It's critical to properly tune the filters (refer to PX4 MC Filter Tuning guide) to ensure stable performance and smooth acceleration measurement - especially while using MC Followapp. Key parameters to adjust:

• IMU_ACCEL_CUTOFF - low pass filter cutoff frequency for accelerometer. Recommendation for use with MC-Follow is 10Hz.

• IMU_GYRO_CUTOFF - low pass filter cutoff frequency for gyroscope. Recommendation for use with MC-Follow is 70Hz.

Air-mode

The multicopter air-mode enables the mixer to increase the total thrust of the vehicle in order to keep attitude and rate control even at low and high throttle. It's recommended to enable air-mode for all three axes as it's necessary to fly highly dynamic trajectories:

• MC_AIRMODE - enables/disables air-mode. Set to 2 to enable air-mode for all three (Yaw/Pitch/Yaw) axes

It is recommended to disable air-mode for the initial flights and during the rate controller tuning process, as an unstable controller could cause a fly-away with air-mode.

Hover and minimum thrust

Hover thrust and minimum thrust is important for altitude mode and landing detection.

For high thrust-to-weight ratio vehicles it's crucial to adjust minimum thrust to prevent false-positive landing detection while still in air:

• MPC_THR_HOVER - thrust required to hover.

• MPC_THR_MIN - minimum collective thrust in climb rate controlled modes (e.g Altitude and Altitude-Cruise). For high thrust-to-weight ratio vehicles, lower the value to 6% (0.06).

• MPC_MANTHR_MIN - minimum collective thrust in Stabilized mode. For high thrust-to-weight ratio vehicles, lower the value to 6% (0.06).

GNSS fusion and barometric altitude

If GNSS receiver is being used, it's recommended to disable GNSS altitude fusion to rely on barometric pressure:

• EKF2_GPS_CTRL - GNSS sensor aiding. Set to 0 to completely disable GNSS fusion (no RTH or Position mode will be available) or set to 5 if GNSS positioning is required.

• EKF2_HGT_REF- reference source of height data used by the EKF. It's recommended to rely on barometric pressure only - set the value to 0 to use barometric pressure as height reference source.

Secure mode and no GNSS data logging

In order to provide additional security it's possible to don't disclose GNSS position in the logs. To enable secure mode use the following parameters:

• COM_SEC_MODE_EN - set to 1 to enable secure mode that will delete information relating to GCS position after landing.

• SDLOG_NO_POS_DAT - set to 1 to disable logging of topics containing absolute position data.

Manual controller configuration

The system can be used with either a joystick connected over AMC or a radio controller (RC) with receiver that supports the CRSF or SBUS protocols.

Joystick

For joystick setup guide refer to Joystick Setup.

Radio controller

Once the receiver is connected according to Hardware integration, proceed with sticks calibration. After successful calibration, go to flight modes tab and assign flight mode channel to desired radio channel.

To enable CRSF telemetry:

• Enable the telemetry: RC_CRSF_TEL_EN -> Enabled (1).

• Reboot the FMU.

Flight modes

Default configuration assigns 3 flight modes to support standard 3-position switch found on most RC controllers. The defaultly modes are as follows:

• 1000 us (usually top most switch position) - Stabilized mode

• 1500us (usually middle switch position) - Altitude mode

• 2000us (usually bottom most switch position) - MC-Follow mode

If other flight modes are desired, these can be configured in the Flight Mode tab.

Arming

The generic airframe config disables arming via stick gesture (due to air-mode on yaw) and thus another arming method has to be used:

• Arming using RC controller switch: assign Arm switch channel in Flight Modes tab.

• Arming over pressing the corresponding button in AMC.

• Arming using Joystick button.