AP_DDS: Add local velocity publisher

libraries/AP_DDS/AP_DDS_Client.cpp

@@ -16,6 +16,7 @@
 static constexpr uint16_t DELAY_TIME_TOPIC_MS = 10;
 static constexpr uint16_t DELAY_BATTERY_STATE_TOPIC_MS = 1000;
 static constexpr uint16_t DELAY_LOCAL_POSE_TOPIC_MS = 33;
+static constexpr uint16_t DELAY_LOCAL_VELOCITY_TOPIC_MS = 33;
 static char WGS_84_FRAME_ID[] = "WGS-84";
 // https://www.ros.org/reps/rep-0105.html#base-link
 static char BASE_LINK_FRAME_ID[] = "base_link";
@@ -295,6 +296,49 @@ void AP_DDS_Client::update_topic(geometry_msgs_msg_PoseStamped& msg)
     }
 }
 
+void AP_DDS_Client::update_topic(geometry_msgs_msg_TwistStamped& msg)
+{
+    update_topic(msg.header.stamp);
+    strcpy(msg.header.frame_id, BASE_LINK_FRAME_ID);
+
+    auto &ahrs = AP::ahrs();
+    WITH_SEMAPHORE(ahrs.get_semaphore());
+
+    // ROS REP 103 uses the ENU convention:
+    // X - East
+    // Y - North
+    // Z - Up
+    // https://www.ros.org/reps/rep-0103.html#axis-orientation
+    // AP_AHRS uses the NED convention
+    // X - North
+    // Y - East
+    // Z - Down
+    // As a consequence, to follow ROS REP 103, it is necessary to switch X and Y,
+    // as well as invert Z
+    Vector3f velocity;
+    if (ahrs.get_velocity_NED(velocity))
+    {
+        msg.twist.linear.x = velocity[1];
+        msg.twist.linear.y = velocity[0];
+        msg.twist.linear.z = -velocity[2];
+    }
+
+    // In ROS REP 103, axis orientation uses the following convention:
+    // X - Forward
+    // Y - Left
+    // Z - Up
+    // https://www.ros.org/reps/rep-0103.html#axis-orientation
+    // The gyro data is received from AP_AHRS in body-frame
+    // X - Forward
+    // Y - Right
+    // Z - Down
+    // As a consequence, to follow ROS REP 103, it is necessary to invert Y and Z
+    Vector3f angular_velocity = ahrs.get_gyro();
+    msg.twist.angular.x = angular_velocity[0];
+    msg.twist.angular.y = -angular_velocity[1];
+    msg.twist.angular.z = -angular_velocity[2];
+}
+
 /*
   class constructor
  */
@@ -502,6 +546,21 @@ void AP_DDS_Client::write_local_pose_topic()
     }
 }
 
+void AP_DDS_Client::write_local_velocity_topic()
+{
+    WITH_SEMAPHORE(csem);
+    if (connected) {
+        ucdrBuffer ub;
+        const uint32_t topic_size = geometry_msgs_msg_TwistStamped_size_of_topic(&local_velocity_topic, 0);
+        uxr_prepare_output_stream(&session,reliable_out,topics[5].dw_id,&ub,topic_size);
+        const bool success = geometry_msgs_msg_TwistStamped_serialize_topic(&ub, &local_velocity_topic);
+        if (!success) {
+            // TODO sometimes serialization fails on bootup. Determine why.
+            // AP_HAL::panic("FATAL: DDS_Client failed to serialize\n");
+        }
+    }
+}
+
 void AP_DDS_Client::update()
 {
     WITH_SEMAPHORE(csem);
@@ -533,6 +592,12 @@ void AP_DDS_Client::update()
         write_local_pose_topic();
     }
 
+    if (cur_time_ms - last_local_velocity_time_ms > DELAY_LOCAL_VELOCITY_TOPIC_MS) {
+        update_topic(local_velocity_topic);
+        last_local_velocity_time_ms = cur_time_ms;
+        write_local_velocity_topic();
+    }
+
     connected = uxr_run_session_time(&session, 1);
 }
 

libraries/AP_DDS/AP_DDS_Client.h

@@ -11,6 +11,7 @@
 #include "tf2_msgs/msg/TFMessage.h"
 #include "sensor_msgs/msg/BatteryState.h"
 #include "geometry_msgs/msg/PoseStamped.h"
+#include "geometry_msgs/msg/TwistStamped.h"
 
 #include <AP_HAL/AP_HAL.h>
 #include <AP_HAL/Scheduler.h>
@@ -48,6 +49,7 @@ private:
     tf2_msgs_msg_TFMessage static_transforms_topic;
     sensor_msgs_msg_BatteryState battery_state_topic;
     geometry_msgs_msg_PoseStamped local_pose_topic;
+    geometry_msgs_msg_TwistStamped local_velocity_topic;
 
     HAL_Semaphore csem;
 
@@ -59,6 +61,7 @@ private:
     static void populate_static_transforms(tf2_msgs_msg_TFMessage& msg);
     static void update_topic(sensor_msgs_msg_BatteryState& msg, const uint8_t instance);
     static void update_topic(geometry_msgs_msg_PoseStamped& msg);
+    static void update_topic(geometry_msgs_msg_TwistStamped& msg);
 
     // The last ms timestamp AP_DDS wrote a Time message
     uint64_t last_time_time_ms;
@@ -68,6 +71,8 @@ private:
     uint64_t last_battery_state_time_ms;
     // The last ms timestamp AP_DDS wrote a Local Pose message
     uint64_t last_local_pose_time_ms;
+    // The last ms timestamp AP_DDS wrote a Local Velocity message
+    uint64_t last_local_velocity_time_ms;
 
 
 public:
@@ -95,6 +100,8 @@ public:
     void write_battery_state_topic();
     //! @brief Serialize the current local pose and publish to the IO stream(s)
     void write_local_pose_topic();
+    //! @brief Serialize the current local velocity and publish to the IO stream(s)
+    void write_local_velocity_topic();
     //! @brief Update the internally stored DDS messages with latest data
     void update();
 

libraries/AP_DDS/AP_DDS_Topic_Table.h

@@ -62,4 +62,14 @@ const struct AP_DDS_Client::Topic_table AP_DDS_Client::topics[] = {
         .deserialize = Generic_deserialize_topic_fn_t(&geometry_msgs_msg_PoseStamped_deserialize_topic),
         .size_of = Generic_size_of_topic_fn_t(&geometry_msgs_msg_PoseStamped_size_of_topic),
     },
+    {
+        .topic_id = 0x06,
+        .pub_id = 0x06,
+        .dw_id = uxrObjectId{.id=0x06, .type=UXR_DATAWRITER_ID},
+        .topic_profile_label = "localvelocity__t",
+        .dw_profile_label = "localvelocity__dw",
+        .serialize = Generic_serialize_topic_fn_t(&geometry_msgs_msg_TwistStamped_serialize_topic),
+        .deserialize = Generic_deserialize_topic_fn_t(&geometry_msgs_msg_TwistStamped_deserialize_topic),
+        .size_of = Generic_size_of_topic_fn_t(&geometry_msgs_msg_TwistStamped_size_of_topic),
+    }
 };

libraries/AP_DDS/dds_xrce_profile.xml

@@ -142,4 +142,32 @@
       </historyQos>
     </topic>
   </data_writer>
+  <topic profile_name="localvelocity__t">
+    <name>rt/ROS2_LocalVelocity</name>
+    <dataType>geometry_msgs::msg::dds_::TwistStamped_</dataType>
+    <historyQos>
+      <kind>KEEP_LAST</kind>
+      <depth>5</depth>
+    </historyQos>
+  </topic>
+  <data_writer profile_name="localvelocity__dw">
+    <historyMemoryPolicy>PREALLOCATED_WITH_REALLOC</historyMemoryPolicy>
+    <qos>
+      <reliability>
+        <kind>BEST_EFFORT</kind>
+      </reliability>
+      <durability>
+        <kind>VOLATILE</kind>
+      </durability>
+    </qos>
+    <topic>
+      <kind>NO_KEY</kind>
+      <name>rt/ROS2_LocalVelocity</name>
+      <dataType>geometry_msgs::msg::dds_::TwistStamped_</dataType>
+      <historyQos>
+        <kind>KEEP_LAST</kind>
+        <depth>5</depth>
+      </historyQos>
+    </topic>
+  </data_writer>
 </profiles>