ardupilot/libraries/AP_DDS/AP_DDS_ExternalControl.cpp

#if AP_DDS_ENABLED

#include "AP_DDS_ExternalControl.h"
#include "AP_DDS_Frames.h"
#include <AP_AHRS/AP_AHRS.h>

#include <AP_ExternalControl/AP_ExternalControl.h>

bool AP_DDS_External_Control::handle_velocity_control(geometry_msgs_msg_TwistStamped& cmd_vel)
{
    auto *external_control = AP::externalcontrol();
    if (external_control == nullptr) {
        return false;
    }

    if (strcmp(cmd_vel.header.frame_id, BASE_LINK_FRAME_ID) == 0) {
        // Convert commands from body frame (x-forward, y-left, z-up) to NED.
        Vector3f linear_velocity;
        Vector3f linear_velocity_base_link {
            float(cmd_vel.twist.linear.x),
            float(cmd_vel.twist.linear.y),
            float(-cmd_vel.twist.linear.z) };
        const float yaw_rate = -cmd_vel.twist.angular.z;

        auto &ahrs = AP::ahrs();
        linear_velocity = ahrs.body_to_earth(linear_velocity_base_link);
        return external_control->set_linear_velocity_and_yaw_rate(linear_velocity, yaw_rate);
    }

    else if (strcmp(cmd_vel.header.frame_id, MAP_FRAME) == 0) {
        // Convert commands from ENU to NED frame
        Vector3f linear_velocity {
            float(cmd_vel.twist.linear.y),
            float(cmd_vel.twist.linear.x),
            float(-cmd_vel.twist.linear.z) };
        const float yaw_rate = -cmd_vel.twist.angular.z;
        return external_control->set_linear_velocity_and_yaw_rate(linear_velocity, yaw_rate);
    }

    return false;
}


#endif // AP_DDS_ENABLED