dongjq23
commented
2 months ago 感谢作者优秀的开源！
因为我应用的场景比较特殊（船舱环境），项目上有一些对地图处理的需求。但是我对于point-lio的理解不够深入，不知道需要怎么修改才能满足我的要求。
我的雷达是mid360，采回来的一些数据包在这里：链接: https://pan.baidu.com/s/1PmE2aJVYI2zvz-Do4kVHZw?pwd=jlu6 提取码: jlu6 播放数据集后，启动 mapping_mid360.launch 文件开始建图。（没有对于任何源码进行修改）
- mid360.yaml文件如下：(因为点云比较多，有做了下采样的预处理，不过yaml里订阅的是原点云)
common:
lid_topic: "/livox/lidar" #"/filtered_cloud/intensity"
imu_topic: "/livox/imu_192_168_1_151"
con_frame: false # true: if you need to combine several LiDAR frames into one
con_frame_num: 1 # the number of frames combined
cut_frame: false # true: if you need to cut one LiDAR frame into several subframes
cut_frame_time_interval: 0.1 # should be integral fraction of 1 / LiDAR frequency
# time_lag_imu_to_lidar: 0.3 # Time offset between LiDAR and IMU calibrated by other algorithms, e.g., LI-Init (find in Readme)
# the timesample of IMU is transferred from the current timeline to LiDAR's timeline by subtracting this value
time_lag_imu_to_lidar: 0.001792 #-0.009263
preprocess:
lidar_type: 2
scan_line: 6
timestamp_unit: 1 # the unit of time/t field in the PointCloud2 rostopic: 0-second, 1-milisecond, 2-microsecond, 3-nanosecond.
blind: 1.0 #0.5
mapping:
imu_en: true
start_in_aggressive_motion: false # if true, a preknown gravity should be provided in following gravity_init
extrinsic_est_en: true # for aggressive motion, set this variable false
imu_time_inte: 0.005 # = 1 / frequency of IMU
# satu_acc: 3.0 # the saturation value of IMU's acceleration. not related to the units
satu_acc: 4.0
satu_gyro: 35 # the saturation value of IMU's angular velocity. not related to the units
acc_norm: 1.0 # 1.0 for g as unit, 9.81 for m/s^2 as unit of the IMU's acceleration
lidar_meas_cov: 0.1 #0.001 # 0.001; 0.01
acc_cov_output: 500
gyr_cov_output: 1000
b_acc_cov: 0.0001
b_gyr_cov: 0.0001
imu_meas_acc_cov: 0.1 #0.1 # 0.1
imu_meas_omg_cov: 0.1 #0.01 # 0.1
gyr_cov_input: 0.01 # for IMU as input model
acc_cov_input: 0.1 # for IMU as input model
plane_thr: 0.1 # 0.05, the threshold for plane criteria, the smaller, the flatter a plane
match_s: 81
fov_degree: 180 #360
det_range: 50.0
#True表示将世界框架的z轴与重力方向对齐，重力方向应在下面指定
gravity_align: false # true to align the z axis of world frame with the direction of gravity, and the gravity direction should be specified below
gravity: [0.0, 0.0, -9.800291] # gravity to be aligned
gravity_init: [0.0, 0.0, -9.800291] # [0.0, 9.810, 0.0] # # preknown gravity in the first IMU body frame, use when imu_en is false or start from a non-stationary state
# extrinsic_T: [ 0.04165, 0.02326, -0.0284 ]
extrinsic_T: [ 0.011, 0.02329, -0.04412 ]
extrinsic_R: [ 1, 0, 0,
0, 1, 0,
0, 0, 1 ]
odometry:
publish_odometry_without_downsample: false
publish:
path_en: true # false: close the path output
scan_publish_en: true # false: close all the point cloud output
scan_bodyframe_pub_en: true # true: output the point cloud scans in IMU-body-frame
pcd_save:
pcd_save_en: true
interval: -1 # how many LiDAR frames saved in each pcd file;
# -1 : all frames will be saved in ONE pcd file, may lead to memory crash when having too much frames.- mapping_mid360.launch文件如下：
<launch>
<!-- Launch file for Livox AVIA LiDAR -->
<arg name="rviz" default="true" />
<node pkg="point_lio" type="pointlio_mapping" name="laserMapping" output="screen">
<rosparam command="load" file="$(find point_lio)/config/mid360.yaml" />
<param name="use_imu_as_input" type="bool" value="0"/> <!--change to 1 to use IMU as input of Point-LIO-->
<param name="prop_at_freq_of_imu" type="bool" value="1"/>
<param name="check_satu" type="bool" value="1"/>
<param name="init_map_size" type="int" value="10"/>
<param name="point_filter_num" type="int" value="1"/> <!--4, 3-->
<param name="space_down_sample" type="bool" value="1" />
<param name="filter_size_surf" type="double" value="0.3" /> <!--0.5, 0.3, 0.2, 0.15, 0.1-->
<param name="filter_size_map" type="double" value="0.2" /> <!--0.5, 0.3, 0.15, 0.1-->
<param name="cube_side_length" type="double" value="2000" /> <!--1000-->
<param name="runtime_pos_log_enable" type="bool" value="0" /> <!--1-->
</node>
<group if="$(arg rviz)">
<node launch-prefix="nice" pkg="rviz" type="rviz" name="rviz" args="-d $(find point_lio)/rviz_cfg/loam_livox.rviz" />
</group>
launch-prefix="gdb -ex run --args"
</launch>问题一：地图绕z轴的偏航角度偏差
建图过程中，效果如下：
因为建图初始帧，imu坐标系与 船舱两垂直侧壁和底面 构成的坐标系不是平行的。所以船舱结构俯视投影与grid map存在偏航角偏差。
我想消除上述的偏差，保持建图过程中，船舱俯视投影与grid map能够水平对齐。我应该如何去做呢？
我能想到的时，在建图初始时刻，保持雷达不动，利用实时的点云数据感知拟合船舱侧壁平面。选定船舱一角以及垂直侧面和舱底面作为坐标系。 计算出IMU坐标系相对于选定的船体坐标系的x y方向偏差，以及偏航角度偏差。
在计算出上述的偏差值之后，我应该将偏差值，写入point-lio源码的哪个位置呢？
下面的建图结束后得到的PCD：
问题二：生成的地图绕x和绕y方向存在3度以内的偏差
问题也是出在初始IMU上，初始点云转换成PCD后查看，就有倾斜的状态。但是无论我在yaml中 设置IMU是否与重力对齐（gravity_align: false 或者 true），都会有倾斜的情况出现。非静止起动情况下，IMU偏转更大，地图生成后偏差也更大。
这是bag数据初始7帧点云叠加的侧视图和正视图：
针对上述的两个问题，您可以帮忙分析一下问题的本质原因和我想的是一样的吗？可以提供一些解决方案嘛？
Joanna-HE
感谢作者优秀的开源！