Using Simple Commander API for multi robot systems (#3803)

* support multirobot namespaces

* add docs

Author: SteveMacenski

nav2_simple_commander/README.md

@@ -14,6 +14,8 @@ See its [API Guide Page](https://navigation.ros.org/commander_api/index.html) fo
 
 The methods provided by the basic navigator are shown below, with inputs and expected returns. If a server fails, it may throw an exception or return a `None` object, so please be sure to properly wrap your navigation calls in try/catch and check results for `None` type.
 
+New as of September 2023: the simple navigator constructor will accept a `namespace` field to support multi-robot applications or namespaced Nav2 launches.
+
 | Robot Navigator Method            | Description                                                                |
 | --------------------------------- | -------------------------------------------------------------------------- |
 | setInitialPose(initial_pose)      | Sets the initial pose (`PoseStamped`) of the robot to localization.        |

nav2_simple_commander/nav2_simple_commander/robot_navigator.py

@@ -46,8 +46,8 @@ class TaskResult(Enum):
 
 class BasicNavigator(Node):
 
-    def __init__(self, node_name='basic_navigator'):
-        super().__init__(node_name=node_name)
+    def __init__(self, node_name='basic_navigator', namespace=''):
+        super().__init__(node_name=node_name, namespace=namespace)
         self.initial_pose = PoseStamped()
         self.initial_pose.header.frame_id = 'map'
         self.goal_handle = None
@@ -83,13 +83,13 @@ def __init__(self, node_name='basic_navigator'):
         self.initial_pose_pub = self.create_publisher(PoseWithCovarianceStamped,
                                                       'initialpose',
                                                       10)
-        self.change_maps_srv = self.create_client(LoadMap, '/map_server/load_map')
+        self.change_maps_srv = self.create_client(LoadMap, 'map_server/load_map')
         self.clear_costmap_global_srv = self.create_client(
-            ClearEntireCostmap, '/global_costmap/clear_entirely_global_costmap')
+            ClearEntireCostmap, 'global_costmap/clear_entirely_global_costmap')
         self.clear_costmap_local_srv = self.create_client(
-            ClearEntireCostmap, '/local_costmap/clear_entirely_local_costmap')
-        self.get_costmap_global_srv = self.create_client(GetCostmap, '/global_costmap/get_costmap')
-        self.get_costmap_local_srv = self.create_client(GetCostmap, '/local_costmap/get_costmap')
+            ClearEntireCostmap, 'local_costmap/clear_entirely_local_costmap')
+        self.get_costmap_global_srv = self.create_client(GetCostmap, 'global_costmap/get_costmap')
+        self.get_costmap_local_srv = self.create_client(GetCostmap, 'local_costmap/get_costmap')
 
     def destroyNode(self):
         self.destroy_node()