Gripper Not Working in Mission Mode – Pixhawk 6C Mini + QGroundControl + PX4 v1.15.4

PX4 Autopilot
1

Hi everyone,
I’m working on a payload drop system using a servo-controlled gripper in a FW drone, and I can’t get it to trigger in mission mode using PX4 and QGroundControl. I have the following settings.

  • Flight Controller: Pixhawk 6C Mini
  • Firmware: PX4 v1.15.4
  • Ground Station: QGroundControl
  • Servo: MG90S Metal Gear
  • Gripper Channel: MAIN4 (mapped to “Gripper” in Actuator tab)
  • PWM Range: 900–2000 µs
  • Power Supply: External BEC
  • Mission Mode: Drone is armed and flying when reaching the command

This is working:

  • The servo works perfectly when tested manually from the Actuator tab in QGroundControl.
  • The MAIN4 output is mapped to “Gripper”.
  • Telemetry confirms the mission reaches the Gripper Mechanism command.

This doesn’t work:

  • When the drone reaches the “Gripper Mechanism” item in mission mode, no PWM signal is sent, and the gripper does not activate.
  • I tried using “Set Servo” instead, but QGroundControl gave this error on mission upload:

Mission transfer failed.
Error: Command is not supported. Item #12 Command: Set servo

Questions

  • Is Gripper Mechanism fully supported in PX4 v1.15.4 for Pixhawk 6C Mini?
  • Should I use Set Actuator instead? If yes, how should I configure it and map the output correctly?
  • Is there any other parameter I may have missed to enable mission-triggered PWM commands?

THANKS!!!