Nav2 is the successor to the ROS Navigation Stack. It enables mobile robots to navigate through complex environments and perform custom tasks with nearly any type of robot kinematics. Nav2 can not only move from Point A to Point B but also handle intermediate waypoints. It provides functions for perception, planning, control, localization, and visualization. It creates an environmental model from sensor and semantic data, dynamically plans paths, calculates motor commands, avoids obstacles, and structures higher-level robot behaviors. As output, Nav2 provides valid velocity commands for the robot's motors.
To control the robot from a PC using Nav2, it is necessary to install Nav2 on the PC. Installation can be carried out using the guide from the following link:
To enable Nav2 to communicate with the Spot Mini, it is necessary to adjust some configurations in the Nav2 parameter file. The file can be found in the project at the following path:
spot-perception/configs/nav2_params.yaml
Since the Spot Mini uses different naming conventions than those used by Nav2 by default, the following lines in the parameter file need to be adjusted to match the naming conventions of the Spot Mini.
The parameters to be adjusted describe the assignment of base_frame, global_frame, local_frame, and the Odometry topic of the spot for nav2:
44 robot_base_frame: hkaspot/body
45 odom_topic: hkaspot/odometry
190 global_frame: hkaspot/odom
191 robot_base_frame: hkaspot/body
227 robot_base_frame: hkaspot/body
306 local_frame: hkaspot/odom
308 robot_base_frame: hkaspot/body
335 odom_topic: "hkaspot/odometry"
342 base_frame_id: "hkaspot/body"
343 odom_frame_id: "hkaspot/odom"Additionally, it is important to note that the plugin assignment in the parameter file uses / instead of :: as originally included. The relevant lines are listed below:
274 plugin: "nav2_navfn_planner/NavfnPlanner"
297 plugin: "nav2_behaviors/Spin"
299 plugin: "nav2_behaviors/BackUp"
301 plugin: "nav2_behaviors/DriveOnHeading"
303 plugin: "nav2_behaviors/Wait"
305 plugin: "nav2_behaviors/AssistedTeleop"With the start of the RTAB-Map Docker, Nav2 is launched with the adjusted nav2_params.yaml through the following line in the entrypoint.
ros2 launch nav2_bringup navigation_launch.py params_file:=spot-perception/configs/nav2_params.yaml
To ensure that the velocity commands output by Nav2 are received by the Spot, additional topic remappings from Nav2 to the Spot's topic need to be applied. This must be done in the navigation_launch.py file at the following path.
spot-perception/launch/navigation_launch.py
The following lines need to be adjusted for this:
135 remappings=remappings + [('cmd_vel', 'hkaspot/cmd_vel')],
168 remappings=remappings + [('cmd_vel', 'hkaspot/cmd_vel')],
202 remappings=remappings + [('cmd_vel', 'hkaspot/cmd_vel')],
238 remappings=remappings + [('cmd_vel', 'hkaspot/cmd_vel')],
259 remappings=remappings + [('cmd_vel', 'hkaspot/cmd_vel')],Once the Docker is started, the Spot Mini can be controlled from an external PC using RViz. The following requirements must be met:
- The PC and the Jetson must be on the same network. The network
ILKA-RoboLab2can be used for this purpose. - The ROS Domain ID of the PC must match that of the Jetson.
To change the ROS Domain ID on the PC, execute the following command in the terminal:
export ROS_DOMAIN_ID=33To check the ROS Domain ID, use the following command:
echo $ROS_DOMAIN_IDThen, RViz can be started on the PC using the following command in the terminal:
ros2 launch nav2_bringup rviz_launch.pyRViz should then open on the PC as shown below:
The following settings should be present on the left side under Display.
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To control the Spot via RViz, ensure that the topics for Description, Topic, and Update Topic match the topics shown in the images.
To navigate, use the Nav2 Goal, which can be found in the selection at the top center. To set a goal, click on the Nav2 Goal selection with the left mouse button and draw a direction arrow on the map while holding down the mouse button. This arrow indicates the desired orientation of the Spot when it arrives at the destination.
It is important to select only white or light-colored areas on the map for navigation, as dark areas represent obstacles. The map shown was taken in the laboratory (ground floor) at LTC.
Once a reachable goal is selected on the map, Nav2 begins planning the path to that goal point. The planned path will be drawn on the map, as shown in the following figure.
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After a short time, the Spot will start moving towards the selected goal point. During navigation, the Spot's position will be continuously updated on the map. Additionally, feedback on the current state of navigation will be displayed in RViz in the following window:
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Since the Spot's localization is done via its odometry and not through Nav2, the Localization status in the RViz window is shown as inactive, as seen in the image.
While Spot has inbuilt collision detection and avoidance, a similar functionality can be achieved using ROS native local costmaps in Nav2. This requires some additional setup in RTAB-Map to recognise and publish obstacles. Details on that can be found in this section
Configuring local costmaps in nav2 for Spot is made easier in this repository. If this functionality is desired, it can be easily enabled in the Nav2 config file under configs/nav2_params.yaml
The following is a short description of all relevant parameters for the local costmap:
190 global_frame: hkaspot/odom # provide odom frame
191 robot_base_frame: hkaspot/body # consider robot name
193 width: 3 # width of costmap frame
194 height: 3 # height of costmap frame
200 cost_scaling_factor: 2.0 # scale cost severity
201 inflation_radius: 0.70 # Inflate obstacle scale
202 obstacle_layer:
204 enabled: False # Set True to enable local costmap
207 topic: /obstacles # topic containing obstacles
212 raytrace_max_range: 10.0 # max distance
214 obstacle_max_range: 5.0 # obstacle render distance
Further details on these and other parameters relevant for costmaps can be obtained here