[Bug] Terrain Following Not Working in PX4 Gazebo Simulation Environment

[serkanMzlm]

Describe the bug

I conduct tests in the PX4 simulation environment before transitioning to the real system. In this case, I added a distance sensor in the simulation and publish its data at 30 Hz to /fmu/in/distance_sensor via ROS2. I can verify that the vehicle receives this data through QGroundControl (QGC). However, even though the sensor values change in uneven terrain, the drone in the simulation does not follow these changes and continues to fly at a constant altitude

using distanceSensorMsg = px4_msgs::msg::DistanceSensor;
...
void DistanceCallback(const laserScanMsg::SharedPtr new_msg)
    {
        RCLCPP_INFO(this->get_logger(), "Distance: %.2f", new_msg->ranges[0]);

        distanceSensorMsg msg;
        msg.timestamp = this->get_clock()->now().nanoseconds() / 1000;
        msg.device_id = 201;
        msg.min_distance = 0.10f;
        msg.max_distance = 220.0f;
        msg.current_distance = new_msg->ranges[0]; // Convert distance to meters
        msg.type = 0;                                             // MAV_DISTANCE_SENSOR_LASER
        msg.h_fov = 0.5 * DEG_TO_RAD;
        msg.v_fov = 0.5 * DEG_TO_RAD;
        msg.orientation = distanceSensorMsg::ROTATION_DOWNWARD_FACING;
        msg.signal_quality = 100;
    
        tf_pub->publish(msg);
    }

Note: Although the sensor data is broadcasting at 30 Hz, it appears as 0.2 Hz in QGC.

To Reproduce

1. Run the Simulation Program
2. uXRCE-DDS is run
3. Parameters set via QGC: EKF2_HGT_REF: 2 (range), MPC_ALT_MODE: 1 (Terrain following)
4. "/fmu/in/distance_sensor" sensor data is published
5. Flights are made over terrain with different heights

Expected behavior

The vehicle should maintain a constant height relative to the ground based on the sensor data.

Screenshot / Media

• First Point

• Second Point

Despite the changes in the sensor data, the vehicle did not correct its distance to the ground

Flight Log

No response

Software Version

PX4: 1.15 version
Simulation: Gazebo Harmonic
ROS2 Humble

Flight controller

simulation

Vehicle type

Multicopter

How are the different components wired up (including port information)

No response

Additional context

No response

[junwoo091400]

Could you share the flight log?

[serkanMzlm]

@junwoo091400 log

When I check the log file in this section, the distance sensor shows 1 meter. However, in the QGC application, the value appears to be fluctuating, and my actual position matches the altitude shown in QGC. The received altitude data is displayed this way on the image

[junwoo091400]

@junwoo091400 log

When I check the parameter for this log, EKF2_HGT_MODE is set to 1, not 2 as you mentioned. Could you recheck if the parameter was indeed properly set during simulation? I suggest modifying the startup script of the airframe to set the parameters you want to set to desired values as vehicle default.

[serkanMzlm]

@junwoo091400 I made the corrections you suggested and tried again, but the flight still does not adjust according to the received distance data

[junwoo091400]

@junwoo091400 I made the corrections you suggested and tried again, but the flight still does not adjust according to the received distance data

Could you share the log for the fixed flight?

[serkanMzlm]

@junwoo091400 The location change can be seen in the distance data, but I cannot change the height of the drone at all. This is the log