add imu soft sync function but not recommended

README.md

@@ -111,6 +111,7 @@ Edit ``` config/avia.yaml ``` to set the below parameters:
 3. Translational extrinsic: ``` extrinsic_T ```
 4. Rotational extrinsic: ``` extrinsic_R ``` (only support rotation matrix)
 - The extrinsic parameters in FAST-LIO is defined as the LiDAR's pose (position and rotation matrix) in IMU body frame (i.e. the IMU is the base frame). They can be found in the official manual.
+- FAST-LIO produces a very simple software time sync for livox LiDAR, set parameter ```time_sync_en``` to ture to turn on. But turn on **ONLY IF external time synchronization is really not possible**, since the software time sync cannot make sure accuracy.
 
 ### 3.3 For Velodyne or Ouster (Velodyne as an example)
 

config/avia.yaml

@@ -1,6 +1,7 @@
 common:
     lid_topic:  "/livox/lidar"
     imu_topic:  "/livox/imu"
+    time_sync_en: false         # ONLY turn on when external time synchronization is really not possible
 
 preprocess:
     lidar_type: 1                # 1 for Livox serials LiDAR, 2 for Velodyne LiDAR, 3 for ouster LiDAR, 

config/horizon.yaml

@@ -1,6 +1,7 @@
 common:
     lid_topic:  "/livox/lidar"
     imu_topic:  "/livox/imu"
+    time_sync_en: false         # ONLY turn on when external time synchronization is really not possible
     
 preprocess:
     lidar_type: 1                # 1 for Livox serials LiDAR, 2 for Velodyne LiDAR, 3 for ouster LiDAR, 

config/ouster64.yaml

@@ -1,6 +1,7 @@
 common:
     lid_topic:  "/os_cloud_node/points"
     imu_topic:  "/os_cloud_node/imu"
+    time_sync_en: false         # ONLY turn on when external time synchronization is really not possible
     
 preprocess:
     lidar_type: 3                # 1 for Livox serials LiDAR, 2 for Velodyne LiDAR, 3 for ouster LiDAR, 

config/velodyne.yaml

@@ -1,6 +1,7 @@
 common:
     lid_topic:  "/velodyne_points"
     imu_topic:  "/imu/data"
+    time_sync_en: false         # ONLY turn on when external time synchronization is really not possible
     
 preprocess:
     lidar_type: 2                # 1 for Livox serials LiDAR, 2 for Velodyne LiDAR, 3 for ouster LiDAR, 

rviz_cfg/loam_livox.rviz

@@ -9,7 +9,6 @@ Panels:
         - /mapping1/surround1
         - /mapping1/currPoints1
         - /mapping1/currPoints1/Autocompute Value Bounds1
-        - /Odometry1
         - /Odometry1/Odometry1
         - /Odometry1/Odometry1/Shape1
         - /Odometry1/Odometry1/Covariance1
@@ -86,9 +85,9 @@ Visualization Manager:
           Enabled: true
           Invert Rainbow: false
           Max Color: 255; 255; 255
-          Max Intensity: 255
+          Max Intensity: 150
           Min Color: 0; 0; 0
-          Min Intensity: 0
+          Min Intensity: 1
           Name: surround
           Position Transformer: XYZ
           Queue Size: 1
@@ -101,7 +100,7 @@ Visualization Manager:
           Use Fixed Frame: true
           Use rainbow: true
           Value: true
-        - Alpha: 0.07000000029802322
+        - Alpha: 0.10000000149011612
           Autocompute Intensity Bounds: true
           Autocompute Value Bounds:
             Max Value: 15
@@ -327,33 +326,33 @@ Visualization Manager:
   Views:
     Current:
       Class: rviz/ThirdPersonFollower
-      Distance: 122.74785614013672
+      Distance: 10
       Enable Stereo Rendering:
         Stereo Eye Separation: 0.05999999865889549
         Stereo Focal Distance: 1
         Swap Stereo Eyes: false
         Value: false
       Focal Point:
-        X: 17.150386810302734
+        X: 5.284592628479004
-        Y: 1.2471342086791992
+        Y: -1.0116491317749023
-        Z: 3.980784458690323e-5
+        Z: -9.5367431640625e-7
-      Focal Shape Fixed Size: true
+      Focal Shape Fixed Size: false
       Focal Shape Size: 0.05000000074505806
-      Invert Z Axis: false
+      Invert Z Axis: true
       Name: Current View
       Near Clip Distance: 0.009999999776482582
-      Pitch: 1.189797043800354
+      Pitch: -0.31460127234458923
       Target Frame: camera_init
       Value: ThirdPersonFollower (rviz)
-      Yaw: 3.293565511703491
+      Yaw: 4.585422039031982
     Saved: ~
 Window Geometry:
   Displays:
     collapsed: false
   Height: 1385
   Hide Left Dock: false
-  Hide Right Dock: true
+  Hide Right Dock: false
-  QMainWindow State: 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
+  QMainWindow State: 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
   Selection:
     collapsed: false
   Time:
@@ -361,7 +360,7 @@ Window Geometry:
   Tool Properties:
     collapsed: false
   Views:
-    collapsed: true
+    collapsed: false
   Width: 2493
   X: 67
   Y: 27

src/laserMapping.cpp

@@ -70,7 +70,7 @@ double kdtree_incremental_time = 0.0, kdtree_search_time = 0.0, kdtree_delete_ti
 double T1[MAXN], s_plot[MAXN], s_plot2[MAXN], s_plot3[MAXN], s_plot4[MAXN], s_plot5[MAXN], s_plot6[MAXN], s_plot7[MAXN], s_plot8[MAXN], s_plot9[MAXN], s_plot10[MAXN], s_plot11[MAXN];
 double match_time = 0, solve_time = 0, solve_const_H_time = 0;
 int    kdtree_size_st = 0, kdtree_size_end = 0, add_point_size = 0, kdtree_delete_counter = 0;
-bool   runtime_pos_log = false, pcd_save_en = false;
+bool   runtime_pos_log = false, pcd_save_en = false, time_sync_en = false;
 /**************************/
 
 float res_last[100000] = {0.0};
@@ -284,22 +284,37 @@ void standard_pcl_cbk(const sensor_msgs::PointCloud2::ConstPtr &msg)
     sig_buffer.notify_all();
 }
 
+double timediff_lidar_wrt_imu = 0.0;
+bool   timediff_set_flg = false;
 void livox_pcl_cbk(const livox_ros_driver::CustomMsg::ConstPtr &msg) 
 {
     mtx_buffer.lock();
-    scan_count ++;
     double preprocess_start_time = omp_get_wtime();
-    cout<<"lidar got at: "<<msg->header.stamp.toSec()<<endl;
+    scan_count ++;
     if (msg->header.stamp.toSec() < last_timestamp_lidar)
     {
         ROS_ERROR("lidar loop back, clear buffer");
         lidar_buffer.clear();
     }
+    last_timestamp_lidar = msg->header.stamp.toSec();
+    
+    if (!time_sync_en && abs(last_timestamp_imu - lidar_end_time) > 10.0)
+    {
+        printf("IMU and LiDAR not Synced, IMU time: %lf, lidar scan end time: %lf",last_timestamp_imu, lidar_end_time);
+    }
+
+    if (time_sync_en && !timediff_set_flg && abs(last_timestamp_lidar - last_timestamp_imu) > 1 && !imu_buffer.empty())
+    {
+        timediff_set_flg = true;
+        timediff_lidar_wrt_imu = last_timestamp_lidar + 0.1 - last_timestamp_imu;
+        printf("Self sync IMU and LiDAR, time diff is %.10lf \n", timediff_lidar_wrt_imu);
+    }
+
     PointCloudXYZI::Ptr  ptr(new PointCloudXYZI());
     p_pre->process(msg, ptr);
     lidar_buffer.push_back(ptr);
-    time_buffer.push_back(msg->header.stamp.toSec());
+    time_buffer.push_back(last_timestamp_lidar);
-    last_timestamp_lidar = msg->header.stamp.toSec();
+    
     s_plot11[scan_count] = omp_get_wtime() - preprocess_start_time;
     mtx_buffer.unlock();
     sig_buffer.notify_all();
@@ -308,18 +323,23 @@ void livox_pcl_cbk(const livox_ros_driver::CustomMsg::ConstPtr &msg)
 void imu_cbk(const sensor_msgs::Imu::ConstPtr &msg_in) 
 {
     publish_count ++;
-    cout<<"IMU got at: "<<msg_in->header.stamp.toSec()<<endl;
+    // cout<<"IMU got at: "<<msg_in->header.stamp.toSec()<<endl;
     sensor_msgs::Imu::Ptr msg(new sensor_msgs::Imu(*msg_in));
 
+    if (abs(timediff_lidar_wrt_imu) > 0.1 && time_sync_en)
+    {
+        msg->header.stamp = \
+        ros::Time().fromSec(timediff_lidar_wrt_imu + msg_in->header.stamp.toSec());
+    }
+
     double timestamp = msg->header.stamp.toSec();
 
     mtx_buffer.lock();
 
     if (timestamp < last_timestamp_imu)
     {
-        ROS_ERROR("imu loop back, clear buffer");
+        ROS_WARN("imu loop back, clear buffer");
         imu_buffer.clear();
-        flg_reset = true;
     }
 
     last_timestamp_imu = timestamp;
@@ -349,11 +369,6 @@ bool sync_packages(MeasureGroup &meas)
         lidar_pushed = true;
     }
 
-    if (abs(last_timestamp_imu - lidar_end_time) > 10.0)
-    {
-        printf("IMU and LiDAR not Synced, IMU time: %lf, lidar scan end time: %lf",last_timestamp_imu, lidar_end_time);
-    }
-
     if (last_timestamp_imu < lidar_end_time)
     {
         return false;
@@ -439,7 +454,6 @@ void publish_frame_world(const ros::Publisher & pubLaserCloudFullRes)
     {
         RGBpointBodyToWorld(&laserCloudFullRes->points[i], \
                             &laserCloudWorld->points[i]);
-        cout<<laserCloudWorld->points[i].intensity<<endl;
     }
 
     // *pcl_wait_pub += *laserCloudWorld;
@@ -664,6 +678,7 @@ int main(int argc, char** argv)
     nh.param<string>("map_file_path",map_file_path,"");
     nh.param<string>("common/lid_topic",lid_topic,"/livox/lidar");
     nh.param<string>("common/imu_topic", imu_topic,"/livox/imu");
+    nh.param<bool>("common/time_sync_en", time_sync_en, false);
     nh.param<double>("filter_size_corner",filter_size_corner_min,0.5);
     nh.param<double>("filter_size_surf",filter_size_surf_min,0.5);
     nh.param<double>("filter_size_map",filter_size_map_min,0.5);
@@ -761,6 +776,7 @@ int main(int argc, char** argv)
                 ROS_WARN("reset when rosbag play back");
                 p_imu->Reset();
                 flg_reset = false;
+                Measures.imu.clear();
                 continue;
             }
 

src/preprocess.cpp

@@ -89,7 +89,7 @@ void Preprocess::avia_handler(const livox_ros_driver::CustomMsg::ConstPtr &msg)
   {
     for(uint i=1; i<plsize; i++)
     {
-      if((msg->points[i].line < N_SCANS) && ((msg->points[i].tag & 0x30) == 0x10))
+      if((msg->points[i].line < N_SCANS) && ((msg->points[i].tag & 0x30) == 0x10 || (msg->points[i].tag & 0x30) == 0x00))
       {
         pl_full[i].x = msg->points[i].x;
         pl_full[i].y = msg->points[i].y;
@@ -138,7 +138,7 @@ void Preprocess::avia_handler(const livox_ros_driver::CustomMsg::ConstPtr &msg)
   {
     for(uint i=1; i<plsize; i++)
     {
-      if((msg->points[i].line < N_SCANS) && ((msg->points[i].tag & 0x30) == 0x10))
+      if((msg->points[i].line < N_SCANS) && ((msg->points[i].tag & 0x30) == 0x10 || (msg->points[i].tag & 0x30) == 0x00))
       {
         valid_num ++;
         if (valid_num % point_filter_num == 0)