ArduPlane: support target airspeed command from DDS

* Similar to MAV_CMD_GUIDED_CHANGE_SPEED

Signed-off-by: Ryan Friedman <[email protected]>

Author: Ryanf55

ArduPlane/AP_ExternalControl_Plane.cpp

@@ -19,4 +19,34 @@ bool AP_ExternalControl_Plane::set_global_position(const Location& loc)
     return plane.set_target_location(loc);
 }
 
+/*
+  Sets the target airspeed.
+*/
+bool AP_ExternalControl_Plane::set_airspeed(const float airspeed)
+{
+#if AP_PLANE_OFFBOARD_GUIDED_SLEW_ENABLED
+    // command is only valid in guided mode
+    if (plane.control_mode != &plane.mode_guided) {
+        return false;
+    }
+
+    if (airspeed > plane.aparm.airspeed_max || airspeed < plane.aparm.airspeed_min) {
+      return false;
+    }
+    plane.guided_state.target_airspeed_cm = airspeed * 100;
+    plane.guided_state.target_airspeed_time_ms = AP_HAL::millis();
+
+    // Assume the user wanted /maximum acceleration, pick a large value as close enough
+    plane.guided_state.target_airspeed_accel = 1000.0f;
+
+    // assign an acceleration direction
+    if (plane.guided_state.target_airspeed_cm < plane.target_airspeed_cm) {
+        plane.guided_state.target_airspeed_accel *= -1.0f;
+    }
+    return true;
+#else 
+  return false;
+#endif
+}
+
 #endif // AP_EXTERNAL_CONTROL_ENABLED

ArduPlane/AP_ExternalControl_Plane.h

@@ -16,6 +16,12 @@ class AP_ExternalControl_Plane : public AP_ExternalControl {
         Sets the target global position for a loiter point.
     */
     bool set_global_position(const Location& loc) override WARN_IF_UNUSED;
+
+    /*
+        Sets the target airspeed.
+    */
+    bool set_airspeed(const float airspeed) override WARN_IF_UNUSED;
+
 };
 
 #endif // AP_EXTERNAL_CONTROL_ENABLED