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NAV350

NAV-350 devices are supported by sick_scan_xd since 2023. Since they support navigation and use a different communication mode, this chapter gives an overview of the NAV-350 support in sick_scan_xd. Please refer to the manuals for further information.

Process loop

Scan data, landmarks and poses of NAV-350 devices are queried by SOPAS commands with polling. Therefore the sick_scan_xd process loop runs as followed:

  1. Initialization and setup

  2. Main loop (polling):
    1 . Send data request "sMN mNPOSGetData 1 2"
    2 . Receive and parse response
    3 . Convert and publish pointcloud, laserscan, landmarks, pose and transform
    4 . API: notify listeners and run their callback functions
    5 . Repeat from step 1

  3. In case of incoming odometry messages (asynchron):
    1 . Convert to SOPAS command
    2 . Send "sMN mNPOSSetSpeed <odom_data>" to NAV350

Initialization and setup

After initialization, sick_scan_xd switches to navigation mode by default. Navigation requires mapping (i.e. a valid landmark layout), which can be done by

  • SOPAS ET (recommended), or
  • optional mapping with parameter nav_do_initial_mapping:=True using the landmarks detected at start, or
  • using an optional imk-file.

Configuration and setup using SOPAS ET is most powerful and recommended.

The default sopas initialization sequence runs as followed:

"sMN SetAccessMode 3 F4724744"     # switch to access level authorized client
"sMN mNEVAChangeState 1"           # switch to operation mode standby
"sWN NEVACurrLayer <layer>"        # set layer configured by launchfile
"sWN NLMDLandmarkDataFormat 0 1 1" # set result format (landmark data)
"sWN NAVScanDataFormat 1 1"        # set result format (scan data)
"sWN NPOSPoseDataFormat 1 1"       # set result format (pose data)
"sMN mNEVAChangeState 4"           # switch to navigation mode
"sMN mNPOSGetData 1 2"             # query pose, landmark and scan data

If optional parameter nav_do_initial_mapping is true, a landmark layout is initialized using the reflectors detected at startup (sopas command "sMN mNMAPDoMapping"). The sopas initialization sequence for an initial mapping runs as followed:

"sMN SetAccessMode 3 F4724744"     # switch to access level authorized client
"sMN mNEVAChangeState 1"           # switch to operation mode standby
"sWN NEVACurrLayer <layer>"        # set layer configured by launchfile
"sWN NLMDLandmarkDataFormat 0 1 1" # set result format (landmark data)
"sWN NAVScanDataFormat 1 1"        # set result format (scan data)
"sWN NPOSPoseDataFormat 1 1"       # set result format (pose data)
"sMN mNEVAChangeState 2"           # switch to mapping mode
"sMN mNLAYEraseLayout 1"           # clear landmark layout
"sWN NMAPMapCfg ..."               # configure mapping parameter
"sWN NLMDReflSize <size>"          # set reflector size configured by launchfile
"sMN mNMAPDoMapping"               # detect landmarks and run mapping
"sMN mNLAYAddLandmark ..."         # add all detected landmarks to the layout
"sMN mNLAYStoreLayout"             # store landmark layout
"sMN mNEVAChangeState 4"           # switch to navigation mode
"sMN mNPOSGetData 1 2"             # query pose, landmark and scan data

The landmark layout stored in an imk-file can optionally loaded at startup with optional parameter nav_set_landmark_layout_by_imk_file. File 20230126_nav350_4reflectors_moving.imk shows an example. See the NAV-350 manual for details about imk-files.

The settings are configured in launchfile sick_nav_350.launch.

Messages

sick_scan_xd polls the NAV350 scan data, reflectors and poses in its main loop. Scan data are published by pointcloud messages (in topic "cloud" by default). Reflectors are published by type sick_scan_xd/NAVLandmarkData on topic "/sick_nav_350/nav_landmark" and as MarkerArray on topic "/sick_nav_350/nav_reflectors" for easy visualization using rviz. Poses are published by type sick_scan_xd/NAVPoseData on topic "/sick_nav_350/nav_pose" and as ros transform on topic "/tf".

The following rviz-screenshot shows the pointcloud, landmarks and pose of a NAV-350:

nav350_ros1_screenshot2.jpg

Odometry messages

Odometry messages can be sent to the NAV-350 device using ROS messages nav_msgs/Odometry on topic "/sick_nav_350/odom" or sick_scan_xd/NAVOdomVelocity on topic "/sick_nav_350/nav_odom_velocity". Odometry messages sick_scan_xd/NAVOdomVelocity specify the velocity (vx, vy) in m/s in lidar coordinates. Odometry messages nav_msgs/Odometry specify the velocity (vx, vy) in m/s in ros coordinates. The angular velocity is expected in radians/s.

Example odometry messages with vx = 1 m/s, vy = -1 m/s and omega: 0.5 rad/s:

rostopic pub --rate 10 /sick_nav_350/nav_odom_velocity sick_scan_xd/NAVOdomVelocity '{vel_x: 1.0, vel_y: -1.0, omega: 0.5, timestamp: 123456789, coordbase: 0}‘
rostopic pub --rate 10 /sick_nav_350/odom nav_msgs/Odometry '{twist: { twist: { linear: {x: 1.0, y: -1.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.5}}}}'