Need some help to use local position from ROS2

[Anders_Gnistrup]

Hi all

I have trying to add a slam camera to a pixhawk 6C via ROS2 using the px4_ros2::LocalPositionMeasurementInterface but it does not work as expected. For simplicity I have start using the simulator gazabo and more to verify my setup.

I have followed the guide ROS 2 User Guide | PX4 Guide (main)

I am using the main branch (v1.16) and start the simulater using ‘make px4_sitl gz_500’.

The gazabo simulation starts up and I can communicate to the drone using QGroundControl. I then start the MicroXRCEAgent to connect to the PX4 client up. A connection is made and all seems to work.I then try to run the offboard example from px4_ros_com, ros2 ‘run px4_ros_com offboard_control’ and it does work. The drone takes off in the simulator.

I then try out the example_local_navigation from px4-ros2-interface-lib. It does compile, starts up but nothing happens. What am i missing? I would have expected to find some updated values in the QGroundControl→Analyze tool→MAVLink inspector in the ODOMETRY but the ODOMETRY is not even present. I have set the EKF2_EV_CTRL and other based n the guide Visual Inertial Odometry (VIO) | PX4 Guide (main)

I think I am close, very close. One idea, should the ros2 translation node be started. My gees is no.

Any help/hint is most appriciated.

Yes, I know this is a bit experimental.

[crazy-robotics]

Have you turned off the GPS from the parameters?

[Anders_Gnistrup]

Sorry for the delay. I have done some further investigation and found some info in two threads.

Sending gps data from Ros 2 to PX4 via Micro XRCE-DDS

Hi @matthewhood14 Yes, a solid yes. when you say You literally want to send raw GPS data, like you have a GPS receiver on your drone? Or the opti track system is acquing local position data, such as x,y,z in some local reference frame and the orientation? because the two approaches are quite different.

It is the same problem I try to solve, like in 1 to 1. I also found this thread. Quite a lot off useful information but not a final recipe/hint.

FastRTPS ROS2 Foxy Vehicle Visual Odometry Advertiser

I increased the baud rate to 921600 and activated HW flow control. Not yet removed the topics I am not using (I suppose you mean on the RPI at the workspace directory of the micrortps_agent and not at the firmware / micrortps_client side). However I still have two questions: Should the MOCAP system subscribe to the PX4 Timesync topic or publish to it? Ideally, to what value should the timestamp_sample variable be set to? EDIT: I subscribed to the VehicleOdometry message. Simply copied the ti…

It is a bit different since it is using the mocap method (external vision, not onboard). But there was some hints about various parameters.

What have I done:

Start MicroXRCEAgent udp4 -p 8888
Start make px4_sitl gz_x500
Start QGroundControl
Set
EKF2_EV_CTRL = 11
EKF2_GPS_CTRL = 0 (no GPS fusion
EKF2_HGT_REF = 3 (height reference coming from EV)

and SYS_HAS_GPS = 0

I have then cloned GitHub - Auterion/px4-ros2-interface-lib: Library to interface with PX4 from a companion computer using ROS 2 and build the example_local_navigatio_cpp applicaten and started it using
ros2 run example_local_navigation_cpp example_local_navigation

I inspected listener vehicle_local_position and listener vehicle_local_odometry. The odometry is updated from the example_local_navigation_cpp. I expected that the submitted data would substitute the GPS but it does not. In the QGroundControl the fmu in “Not Ready”.

The data generated in the example_local_navigation_cpp is:

static int count;
count++;
px4_ros2::LocalPositionMeasurement local_position_measurement {};
local_position_measurement.timestamp_sample = _node.get_clock()->now();
local_position_measurement.velocity_xy = Eigen::Vector2f {1.f, 2.f};
local_position_measurement.velocity_xy_variance = Eigen::Vector2f {0.3f, 0.4f};
local_position_measurement.position_z = 12.8f + count / 1000.f;
local_position_measurement.position_z_variance = 0.33F;
local_position_measurement.attitude_quaternion = Eigen::Quaternionf {0.1, -0.2, 0.3, 0.25};
local_position_measurement.attitude_variance = Eigen::Vector3f {0.2, 0.1, 0.05};

I have added count++ to see that “something” is updated in the odometry data in the pxh console. It does update in odometry date. It does not seems to make any change to the TOPIC: vehicle_local_position data.

So, what is missing? I think I am very close.

[Anders_Gnistrup]

Minor update. I have tried to use make px4_sitl gz_x500_vision and that works with the settings above. I when tried to run the offboard example and it did take off.
So I assume that the parameters is OK but “something” is missing in the example_local_navigation_cpp. That “something” is set when running the xx_vision. I would assumed that the example_local_navigation_cpp and vision should do the same thing.