MAVROS & ROS2 offboard control with new dynamic mixing system

ayham · August 8, 2022, 12:17pm

Hello everyone,

I would like to ask if there is a ‘ready’ solution to send in 3D force & 3D torque commands to the new dynamic mixing system to control a fully/over-actuated multirotor (with MAVROS or ROS2).

I am trying to control a fully/over-actuated multirotor with an offboard controller running in ROS(1 or 2), and the output of this controller will be a 6D wrench (3D force & 3D torque) then the new mixing system will handle the control allocation.

To be clear, I do not want to use the PX4 cascaded controllers.

Currently, with standard quad/hexarotor, we use MAVROS ActuatorControl messages to send the normalized 3D torque and thrust commands to the old mixing system, and we want to use a similar approach with the new mixing system to control fully/over-actuated multirotors.

@sfuhrer & @bkueng can you please advise us about this?

Best,
Ayham Alharbat

bkueng · August 9, 2022, 5:54am

Hi

The simplest for now is to publish the actuator thrust and torque topics when receiving the ActuatorControl message if the dynamic mixing is enabled.
It’s these 2 topics:

github.com

PX4/PX4-Autopilot/blob/main/msg/vehicle_thrust_setpoint.msg


uint64 timestamp        # time since system start (microseconds)
uint64 timestamp_sample # timestamp of the data sample on which this message is based (microseconds)

float32[3] xyz          # thrust setpoint along X, Y, Z body axis [-1, 1]

github.com

PX4/PX4-Autopilot/blob/main/msg/vehicle_torque_setpoint.msg


uint64 timestamp        # time since system start (microseconds)
uint64 timestamp_sample # timestamp of the data sample on which this message is based (microseconds)

float32[3] xyz          # torque setpoint about X, Y, Z body axis (normalized)

ayham · August 9, 2022, 8:25am

Hi @bkueng,

Thanks for the quick response! I have a follow-up question:

Do these commands have to be normalized? I thought that you will be giving up the ‘normalization’ of these signals according to this presentation.

bkueng · August 9, 2022, 8:51am

Yes we still use normalized values for now.