fix(nav2): improve mkmini gazebo steering simulation

src/nav2_turtlebot_simulator/launch/simulator.launch.py

@@ -220,21 +220,33 @@ def create_mkmini_world(gazebo_dir):
         except ValueError:
             continue
 
-    # The MKMini lidar is centered at 0.52 m. Raise the original 0.5 m white
-    # pillars so they remain observable obstacles instead of falling below the
-    # scan plane.
-    for element in (*model.findall('.//collision'), *model.findall('.//visual')):
-        cylinder = element.find('./geometry/cylinder')
-        if cylinder is None:
-            continue
-        if cylinder.findtext('radius') != '0.15' or cylinder.findtext('length') != '0.5':
-            continue
-        cylinder.find('length').text = '1.2'
-        pose = element.find('pose')
-        if pose is None:
-            continue
-        values = pose.text.split()
-        if len(values) == 6:
+    # Keep only the centre post from TurtleBot3 World's 3x3 white-pillar grid.
+    # This is applied to the generated MKMini world only; Burger keeps the
+    # original obstacle layout. Remove both visual and collision shapes so the
+    # Gazebo scene and Nav2 costmap describe the same space.
+    for link in model.findall('.//link'):
+        for element in list(link):
+            if element.tag not in {'collision', 'visual'}:
+                continue
+            cylinder = element.find('./geometry/cylinder')
+            if cylinder is None:
+                continue
+            if cylinder.findtext('radius') != '0.15' or cylinder.findtext('length') != '0.5':
+                continue
+            pose = element.find('pose')
+            values = pose.text.split() if pose is not None and pose.text else []
+            if len(values) != 6:
+                continue
+            try:
+                x, y = float(values[0]), float(values[1])
+            except ValueError:
+                continue
+            if abs(x) > 1e-6 or abs(y) > 1e-6:
+                link.remove(element)
+                continue
+            # The MKMini lidar is centered at 0.52 m. Raise the remaining
+            # centre post so it stays observable instead of below the scan.
+            cylinder.find('length').text = '1.2'
             values[2] = '0.6'
             pose.text = ' '.join(values)