Using 2 velodynes, receiving mixed messages in separated topics from both velodynes

[yasgalmon]

• OS and Version: Ubuntu 18.04
• ROS Version: Melodic
• Built from Source or Downloaded from Official Repository: Built from source
• Version: Commit 75c7c68 I'm trying to receive messages from two velodynes and then merge the scans for using the data with AMCL package. I've modified the launcher so the velodyne's scan topic is ${arg frame_id}_scan instead of just scan and I've realized that I'm receiving in each velodyne's topic mixed messages from both velodynes instead of the ones corresponding to the velodyne of the topic. Does anyone had this problem and can tell me how to solve it? Thank you in advance.

Modified launcher:

<!-- run velodyne_pointcloud/CloudNodelet in a nodelet manager for a VLP-16 -->

<launch>

  <!-- declare arguments with default values -->
  <arg name="calibration" default="$(find velodyne_pointcloud)/params/VLP16db.yaml"/>
  <arg name="device_ip" default="" />
  <arg name="frame_id" default="velodyne" />
  <arg name="manager" default="$(arg frame_id)_nodelet_manager" />
  <arg name="max_range" default="130.0" />
  <arg name="min_range" default="0.4" />
  <arg name="pcap" default="" />
  <arg name="port" default="2368" />
  <arg name="read_fast" default="false" />
  <arg name="read_once" default="false" />
  <arg name="repeat_delay" default="0.0" />
  <arg name="rpm" default="600.0" />
  <arg name="gps_time" default="false" />
  <arg name="cut_angle" default="-0.01" />
  <arg name="timestamp_first_packet" default="false" />
  <arg name="laserscan_ring" default="-1" />
  <arg name="laserscan_resolution" default="0.007" />
  <arg name="organize_cloud" default="false" />
  <!--
     0    degrees >>>>      0.0 rad     >>>> FRONTAL
    180  degrees >>>> 3.14159265359 rad >>>> REAR
  -->
  <arg name="view_direction" default="0.0" /><!--[0-2*pi]center of view angle in radians in the device frame of reference.-->
  <!--
    240 degrees >>>> 4.18879000000 rad
    220 degrees >>>> 3.83972000000 rad
    200 degrees >>>> 3.49066000000 rad
    180 degrees >>>> 3.14159265359 rad
    160 degrees >>>> 2.79252680319 rad 
    140 degrees >>>> 2.44346095279 rad
    120 degrees >>>> 2.09439510239 rad
  -->
  <arg name="view_width" default="3.83972000000" /><!--[0-2*pi]Width of view angle in radians in the XY plane of the device frame of reference-->

  <!-- start nodelet manager and driver nodelets -->
  <include file="$(find velodyne_driver)/launch/nodelet_manager.launch">
    <arg name="device_ip" value="$(arg device_ip)"/>
    <arg name="frame_id" value="$(arg frame_id)"/>
    <arg name="manager" value="$(arg manager)" />
    <arg name="model" value="VLP16"/>
    <arg name="pcap" value="$(arg pcap)"/>
    <arg name="port" value="$(arg port)"/>
    <arg name="read_fast" value="$(arg read_fast)"/>
    <arg name="read_once" value="$(arg read_once)"/>
    <arg name="repeat_delay" value="$(arg repeat_delay)"/>
    <arg name="rpm" value="$(arg rpm)"/>
    <arg name="gps_time" value="$(arg gps_time)"/>
    <arg name="cut_angle" value="$(arg cut_angle)"/>
    <arg name="timestamp_first_packet" value="$(arg timestamp_first_packet)"/>
  </include>

  <!-- start cloud nodelet -->
  <include file="$(find velodyne_pointcloud)/launch/cloud_nodelet.launch">
    <arg name="model" value="VLP16"/>
    <arg name="calibration" value="$(arg calibration)"/>
    <arg name="manager" value="$(arg manager)" />
    <arg name="fixed_frame" value="$(arg frame_id)" />
    <arg name="target_frame" value="$(arg frame_id)" />
    <arg name="max_range" value="$(arg max_range)"/>
    <arg name="min_range" value="$(arg min_range)"/>
    <arg name="organize_cloud" value="$(arg organize_cloud)"/>
    <arg name="view_width" value="$(arg view_width)"/>
    <arg name="view_direction" value="$(arg view_direction)"/>
  </include>

  <!-- start laserscan nodelet -->
  <include file="$(find velodyne_pointcloud)/launch/laserscan_nodelet.launch">
    <arg name="manager" value="$(arg manager)" />
    <arg name="ring" value="$(arg laserscan_ring)"/>
    <arg name="resolution" value="$(arg laserscan_resolution)"/>
  </include>

</launch>

Launch script:

# Local variables for script purposes
NOT_FOUND=true
ALL_OK=false
NUM_LIDARS=0
# All velodyne data are stored in an array called LIDAR
declare -A LIDAR

if [ -z $CAR_TYPE ]; then
    echo "CAR_TYPE variable not set. Try adding to ~/.bashrc the following command: export CAR_TYPE=cas (cas/c4/golf)\n"
    exit 1
else
    if [ $CAR_TYPE = "cas" ]; then
        echo "CAR_TYPE selected is cas"
        # The data of the velodyne in the front of the CAS is stored in FRONT
        declare -A FRONT
        # The data of the velodyne in the back of the CAS is stored in BACK
        declare -A BACK
        # FRONT velodyne data
        FRONT["IP"]=192.168.1.91
        FRONT["FRAME_ID"]=front_velodyne
        FRONT["PORT"]=2368
        FRONT["RPM"]=1200.0
        FRONT["RING"]=12
        FRONT["VIEW_DIRECTION"]=0.0
        FRONT["VIEW_WIDTH"]=3.14159265359
        FRONT["PING"]=false
        FRONT["COUNT"]=0
        # BACK velodyne data
        BACK["IP"]=192.168.1.201
        BACK["FRAME_ID"]=back_velodyne
        BACK["PORT"]=2368
        BACK["RPM"]=1200.0
        BACK["RING"]=12
        BACK["VIEW_DIRECTION"]=1,57079632679
        BACK["VIEW_WIDTH"]=3.14159265359
        BACK["PING"]=false
        BACK["COUNT"]=0
        # FRONT and BACK are stored in LIDAR
        i=1
        for key in "${!FRONT[@]}"; do
            LIDAR[$i,$key]=${FRONT[$key]}
        done
        ((i++))
        for key in "${!BACK[@]}"; do
            LIDAR[$i,$key]=${BACK[$key]}
        done
        declare -p LIDAR
        NUM_LIDARS=2
    fi
    if [ $CAR_TYPE = "c4" ]; then
        echo "CAR_TYPE selected is c4"
        # The data of the velodyne is stored in FRONT
        declare -A FRONT
        # FRONT velodyne data
        FRONT["IP"]=192.168.1.201
        FRONT["FRAME_ID"]=velodyne
        FRONT["PORT"]=2369
        FRONT["RPM"]=1200.0
        FRONT["RING"]=7
        FRONT["VIEW_DIRECTION"]=0.0
        FRONT["PING"]=false
        FRONT["COUNT"]=0
        FRONT["VIEW_WIDTH"]=6,28318530718
        # FRONT is stored in LIDAR
        i=1
        for key in "${!FRONT[@]}"; do
            LIDAR[$i,$key]=${FRONT[$key]}
        done
        declare -p LIDAR
        NUM_LIDARS=1
    fi
fi
if [ -z $TEST_WITH_PCAP ]; then
    echo "No PCAP file detected. Trying to connect to VLP16 sensors"
    until $ALL_OK; do
        i=1
        while [ $i -le $NUM_LIDARS ]; do
            ALL_OK=true
            if [ !${LIDAR[$i, PING]} ]; then
                ping -q -c3 "${LIDAR[$i,IP]}" > /dev/null
                if [ $? -eq 0 ]; then
                    echo "Succeded to ping VLP16 ${LIDAR[$i,IP]}\nLaunching Driver...\n"
                    roslaunch velodyne_pointcloud VLP16_points.launch device_ip:=${LIDAR[$i,IP]} frame_id:=${LIDAR[$i,FRAME_ID]} port:=${LIDAR[$i,PORT]} rpm:=${LIDAR[$i,RPM]} laserscan_ring:=${LIDAR[$i,RING]} view_direction:=${LIDAR[$i,VIEW_DIRECTION]} view_width:=${LIDAR[$i,VIEW_WIDTH]} &
                    LIDAR[$i,PING]=true
                    LIDAR[$i,COUNT]=0
                    sleep 2s
                else
                    echo "No ping from VLP16 (${LIDAR[$i,IP]})"
                    if [ $( ifconfig | grep addr:192.168.1.14| wc -l) -lt 1 ]; then
                        printf "Not connected to velodyne network\n"
                    fi    
                    LIDAR[$i,COUNT]=$((LIDAR[$i,COUNT]+1))
                    printf "Ping not established, attempt number: ${LIDAR[$i,COUNT]} \n" 
                    ALL_OK=false 
                fi
            fi
        ((i++))
        done
    done
else
    echo "Using file: $TEST_WITH_PCAP"
    i=1
    while [ $i -le $NUM_LIDARS ]; do
        echo "Launching driver for VLP16 (${LIDAR[$i,IP]})"
        roslaunch velodyne_pointcloud VLP16_points.launch device_ip:=${LIDAR[$i,IP]} frame_id:=${LIDAR[$i,FRAME_ID]} port:=${LIDAR[$i,PORT]} pcap:=${EST_WITH_PCAP} rpm:=${LIDAR[$i,RPM]} laserscan_ring:=${LIDAR[$i,RING]} view_direction:=${LIDAR[$i,VIEW_DIRECTION]} view_width:=${LIDAR[$i,VIEW_WIDTH]} &
        ((i++))
        sleep 2s
    done
fi
exit 0

[JWhitleyWork]

You should, instead, launch each driver in its own namespace (e.g. /lidar1/velodyne_driver, /lidar2/velodyne_driver) and then you'll need to combine the two scans into one using a fusion node. An example of one can be found in Autoware.Auto.

[jeff-o]

Make sure you define different ports for each sensor. Currently it looks like both are using 2368. So set one of them to 2369 (or some other unused port).