镭神激光雷达对于Autoware的适配

1. 前言

我们的自动驾驶采用镭神激光雷达，在使用Autoware的时候，需要对镭神激光雷达的底层驱动，进行一些改变以适配Autoware。

2. 修改

（1）首先修改lslidar_c32.launch文件：

<launch>

  <node pkg="lslidar_c32_driver" type="lslidar_c32_driver_node" name="leishen_lslidar_c32_driver" output="screen" >
    <param name="frame_id" value="laser_link"/>
    <param name="device_ip" value="192.168.1.200"/>
    <param name="device_port" value="2368"/>
  </node>

  <node pkg="lslidar_c32_decoder" type="lslidar_c32_decoder_node" name="leishen_lslidar_c32_decoder" output="screen">
    <!-- <param name="child_frame_id" value="world"/> -->
    <param name="child_frame_id" value="velodyne"/>
    <param name="point_num" value="2000"/>
    <param name="channel_num" value="0"/>
    <param name="angle_disable_min" value="0"/>
    <param name="angle_disable_max" value="0"/>
    <param name="min_range" value="0.15"/>
    <param name="max_range" value="500.0"/>
    <param name="frequency" value="10.0"/>
    <param name="publish_point_cloud" value="true"/>
    <param name="publish_channels" value="false"/>
    <remap from="lslidar_point_cloud" to="/points_raw" />
  </node>
  
  <!--node name="rviz" pkg="rviz" type="rviz" args="-d $(find lslidar_c32_decoder)/launch/lslidar_c32.rviz" output="screen"/-->

</launch>

这里贴出了修改后的launch文件，第10行修改为11行，21行去掉s。我们修改了frame_id，将之前的“world”改为“velodyne”。还有就是Autoware需要的点云topic为points_raw，而镭神的点云topic为point_raw，我们讲point_raw改为points_raw。

（2）修改时间戳

根据镭神的手册：“如果镭神接入GPS，那么会采用GPS时间，如果不接入GPS，雷达会采用内部时间，从0开始以微秒为单位计数，计数值赋值到主数据流时间戳的字节，计数到1小时在从0开始”。这样会导致在使用TF变换的时候时间戳出错，所以，需要修改时间戳，找到如下代码

void LslidarC32Decoder::publishPointCloud() {
//    pcl::PointCloud<pcl::PointXYZI>::Ptr point_cloud(
//                new pcl::PointCloud<pcl::PointXYZI>());
    VPointCloud::Ptr point_cloud(new VPointCloud());

    //point_cloud->header.stamp =
            //pcl_conversions::toPCL(sweep_data->header).stamp;
    point_cloud->header.frame_id = child_frame_id;
    point_cloud->height = 1;

    for (size_t i = 0; i < 32; ++i) {
        const lslidar_c32_msgs::LslidarC32Scan& scan = sweep_data->scans[i];
        // The first and last point in each scan is ignored, which
        // seems to be corrupted based on the received data.
        // TODO: The two end points should be removed directly
        //    in the scans.
        // point_time unit is sec
        double timestamp = point_time;
        //point_cloud->header.stamp = static_cast<uint64_t>(timestamp * 1e6);
        point_cloud->header.stamp = ros::Time::now().toSec() * 1e6; 
        if (scan.points.size() == 0) continue;
        size_t j;
        VPoint point;
        for (j = 1; j < scan.points.size()-1; ++j) {
            point.timestamp = timestamp - (scan.points.size()-1 - j)*0.00005;  // time interval for each point is 50us
            point.x = scan.points[j].x;
            point.y = scan.points[j].y;
            point.z = scan.points[j].z;
            point.intensity = scan.points[j].intensity;
            point.range = scan.points[j].distance;
            point.h_angle = scan.points[j].azimuth;
            point.v_angle = layer_altitude[i];
            point.laserid = layer_id[i];

            point_cloud->points.push_back(point);
            ++point_cloud->width;
        }

    }

    //      if(point_cloud->width > 2000)
    {
        point_cloud_pub.publish(point_cloud);
    }


    return;
}

同样是贴上修改后的代码，将19行变为20行。