Add robot name modification feature to change_urdf_root command (#570)

When changing the root link of a URDF that was generated from xacro modules,
the robot name now automatically changes to reflect the new root configuration.
This prevents naming conflicts when using modularize-urdf to convert the
modified URDF back to xacro format.

Previously, when converting a root-changed URDF to xacro using modularize-urdf,
the generated macro would have the same name as the original, causing conflicts
when trying to use both the original and root-changed versions in the same
xacro file.

Changes:
- Auto-generate new robot name as "{original}_root_{new_root_link}" by default
- Add --robot-name option for custom robot names
- Add --keep-robot-name option to preserve the original name
- Update URDFXMLRootLinkChanger to support robot name modification

Author: iory

skrobot/apps/change_urdf_root.py

@@ -28,6 +28,12 @@ def main():
 
   # Change root link with verbose output
   change_urdf_root robot.urdf new_root output.urdf --verbose
+
+  # Change root link with custom robot name
+  change_urdf_root robot.urdf new_root output.urdf --robot-name my_robot
+
+  # Keep original robot name
+  change_urdf_root robot.urdf new_root output.urdf --keep-robot-name
         """)
 
     parser.add_argument(
@@ -62,6 +68,16 @@ def main():
         action='store_true',
         help='Overwrite output file if it exists')
 
+    parser.add_argument(
+        '--robot-name',
+        type=str,
+        help='Custom robot name for the output URDF')
+
+    parser.add_argument(
+        '--keep-robot-name',
+        action='store_true',
+        help='Keep the original robot name (do not auto-generate new name)')
+
     args = parser.parse_args()
 
     # Check if input file exists
@@ -80,8 +96,10 @@ def main():
         # If --list is specified, show all links and exit
         if args.list:
             current_root = changer.get_current_root_link()
+            robot_name = changer.get_robot_name()
             links = changer.list_links()
 
+            print("Robot name: {}".format(robot_name))
             print("Current root link: {}".format(current_root))
             print("Total links: {}".format(len(links)))
             print("\nAll links:")
@@ -122,7 +140,21 @@ def main():
 
         # Show current state
         current_root = changer.get_current_root_link()
+        current_robot_name = changer.get_robot_name()
+
+        # Determine robot name for output
+        if args.keep_robot_name:
+            output_robot_name = current_robot_name
+        elif args.robot_name:
+            output_robot_name = args.robot_name
+        else:
+            # Default: auto-generate based on new root link
+            output_robot_name = "{}_root_{}".format(
+                current_robot_name, args.new_root_link)
+
         if args.verbose:
+            print("Current robot name: {}".format(current_robot_name))
+            print("New robot name: {}".format(output_robot_name))
             print("Current root link: {}".format(current_root))
             print("New root link: {}".format(args.new_root_link))
             print("Output file: {}".format(args.output_urdf))
@@ -137,18 +169,31 @@ def main():
         if args.verbose:
             print("Changing root link...")
 
-        changer.change_root_link(args.new_root_link, args.output_urdf)
+        # Pass robot name (either custom or None for auto-generation)
+        if args.keep_robot_name:
+            changer.change_root_link(args.new_root_link, args.output_urdf,
+                                     robot_name=current_robot_name)
+        elif args.robot_name:
+            changer.change_root_link(args.new_root_link, args.output_urdf,
+                                     robot_name=args.robot_name)
+        else:
+            # Let the changer auto-generate the name
+            changer.change_root_link(args.new_root_link, args.output_urdf)
 
         # Verify the result
         if args.verbose:
             print("Verifying result...")
 
         result_changer = URDFXMLRootLinkChanger(args.output_urdf)
         actual_root = result_changer.get_current_root_link()
+        actual_robot_name = result_changer.get_robot_name()
 
         if actual_root == args.new_root_link:
             print("Successfully changed root link from '{}' "
                   "to '{}'".format(current_root, args.new_root_link))
+            if current_robot_name != actual_robot_name:
+                print("Robot name changed from '{}' to '{}'".format(
+                    current_robot_name, actual_robot_name))
             print("Modified URDF saved to: {}".format(args.output_urdf))
         else:
             print("Failed to change root link. Expected "

skrobot/urdf/xml_root_link_changer.py

@@ -124,7 +124,7 @@ def list_links(self):
         """
         return list(self.links.keys())
 
-    def change_root_link(self, new_root_link, output_path):
+    def change_root_link(self, new_root_link, output_path, robot_name=None):
         """Change the root link and save the modified URDF.
 
         Parameters
@@ -133,6 +133,9 @@ def change_root_link(self, new_root_link, output_path):
             Name of the new root link
         output_path : str
             Path where the modified URDF will be saved
+        robot_name : str, optional
+            New robot name. If None, generates a default name based on
+            the original robot name and new root link.
 
         Raises
         ------
@@ -144,8 +147,13 @@ def change_root_link(self, new_root_link, output_path):
                 "Link '{}' not found in URDF".format(new_root_link))
 
         current_root = self.get_current_root_link()
+
+        # Set robot name if needed
+        if robot_name is not None or new_root_link != current_root:
+            self._set_robot_name(robot_name, new_root_link)
+
         if new_root_link == current_root:
-            # No change needed, just copy the file
+            # No change needed to kinematic tree, just save with new name
             self._save_urdf(output_path)
             return
 
@@ -476,6 +484,33 @@ def _save_urdf(self, output_path):
         # Format the output for better readability
         self._format_xml_file(output_path)
 
+    def get_robot_name(self):
+        """Get the current robot name.
+
+        Returns
+        -------
+        str
+            Current robot name, or 'robot' if not set
+        """
+        return self.root.get('name', 'robot')
+
+    def _set_robot_name(self, robot_name, new_root_link):
+        """Set the robot name.
+
+        Parameters
+        ----------
+        robot_name : str or None
+            New robot name. If None, generates default name.
+        new_root_link : str
+            Name of the new root link (used for default naming)
+        """
+        if robot_name is None:
+            # Generate default name: original_name_root_new_root_link
+            original_name = self.get_robot_name()
+            robot_name = "{}_root_{}".format(original_name, new_root_link)
+
+        self.root.set('name', robot_name)
+
     def _format_xml_file(self, file_path):
         """Format XML file for better readability.
 
@@ -504,7 +539,7 @@ def _format_xml_file(self, file_path):
             pass
 
 
-def change_urdf_root_link(urdf_path, new_root_link, output_path):
+def change_urdf_root_link(urdf_path, new_root_link, output_path, robot_name=None):
     """Change the root link of a URDF file.
 
     Parameters
@@ -515,6 +550,8 @@ def change_urdf_root_link(urdf_path, new_root_link, output_path):
         Name of the new root link
     output_path : str
         Path where the modified URDF will be saved
+    robot_name : str, optional
+        New robot name. If None, generates a default name.
     """
     changer = URDFXMLRootLinkChanger(urdf_path)
-    changer.change_root_link(new_root_link, output_path)
+    changer.change_root_link(new_root_link, output_path, robot_name=robot_name)