之前博客《ROS學習筆記之——DAVIS346 calibration》已經實作了用dv-gui（Calibration [Tutorial] · DV）來標定event camera了，但是缺少了跟IMU的外參標定等等，本博文利用Kalibr庫來對其進行標定，

Kalibr安裝

先創建一個作業空間

mkdir -p ~/kalibr_workspace/src
cd ~/kalibr_workspace
source /opt/ros/melodic/setup.bash
catkin init
catkin config --extend /opt/ros/melodic
catkin config --merge-devel
catkin config --cmake-args -DCMAKE_BUILD_TYPE=Release

cd ~/kalibr_workspace/src
git clone https://github.com/ethz-asl/Kalibr.git

cd ~/kalibr_workspace
catkin build -DCMAKE_BUILD_TYPE=Release -j4

可能會提示缺少libv4l，安裝依賴包即可：

sudo apt-get install libv4l-dev

建立完之后需要source一下

source ~/kalibr_workspace/devel/setup.bash

還是沒有辦法，，，，還要把操蛋的opencv4安裝了，，，，，

改為參考：melodic 安裝 kalibr_matthewsyc的博客-CSDN博客

sudo apt-get install python-setuptools python-rosinstall ipython 
sudo apt-get install libeigen3-dev libboost-all-dev doxygen
sudo apt-get install ros-melodic-cmake-modules python-software-properties 
sudo apt-get install software-properties-common libpoco-dev python-matplotlib 
sudo apt-get install python-scipy python-git python-pip ipython libtbb-dev 
sudo apt-get install libblas-dev liblapack-dev python-catkin-tools libv4l-dev
sudo apt-get install python-igraph

安裝完依賴后，編譯好像就比較正常了～

每次運行前，記得加入

source ~/kalibr_workspace/devel/setup.bash

IMU標定

產生資料寫入imu.yaml中，imu.yaml檔案要用于聯合標定，

imu_utils依賴code_utils，要先安裝code_utils再安裝imu_utils，

mkdir -p ~/imu_catkin_ws/src
cd ~/imu_catkin_ws/src
catkin_init_workspace
cd ..
catkin_make
source ~/imu_catkin_ws/devel/setup.bash

cd ~/imu_catkin_ws/src
git clone https://github.com/gaowenliang/code_utils.git
cd ..
catkin_make

可能出現報錯，試試運行

sudo apt-get install libdw-dev

catkin_make時出現backward.hpp沒有找到

解決方法：將sumpixel_test.cpp中# include "backward.hpp"改為：#include “code_utils/backward.hpp”

即可安裝成功！

然后下載imu_utils

cd ~/imu_catkin_ws/src/
git clone https://github.com/gaowenliang/imu_utils.git
cd ..
catkin_make

然后運行

roslaunch vins davis_testing.launch

rostopic list

rostopic echo /dvs/imu

記錄imu資訊，這個程序要保持imu靜止不動至少２個小時(這個太夸張了吧，，，)

17.26開始

在imu_utils檔案下的launch檔案目錄下添加一個launch檔案，我這里添加的是 imu.launch，并把以下代碼復制進檔案，代碼中的/IMU_data改成自己imu的topic，

<launch>
    <node pkg="imu_utils" type="imu_an" name="imu_an" output="screen">
        <!--TOPIC名稱-->
        <param name="imu_topic" type="string" value= "/dvs/imu"/>
        <!--imu_name 無所謂-->
        <param name="imu_name" type="string" value= "imu_davis346"/>
         <!--標定結果存放路徑-->s
        <param name="data_save_path" type="string" value= "$(find imu_utils)/data/"/>
        <!--資料錄制時間-min-->
        <param name="max_time_min" type="int" value= "120"/>
         <!--采樣頻率，即是IMU頻率，采樣頻率可以使用rostopic hz /dvs/imu查看，設定為400，為后面的rosbag play播放頻率-->
        <param name="max_cluster" type="int" value= "400"/>
    </node>
</launch>

運行之前要先source一下

source ~/imu_catkin_ws/devel/setup.bash
roslaunch imu_utils davis_imu.launch
rosbag play -r 400 /home/kwanwaipang/dataset/gwphku/hku_davis346_imu_2021-10-25-17-26-06.bag
rosbag play /home/kwanwaipang/dataset/gwphku/hku_davis346_imu_2021-10-25-17-26-06.bag

標定結束后在imu_catkin_ws/src/imu_utils/data中生成許多檔案，其中(d435i_imu_param.yaml)imu_davis346_imu_param.yaml就是我們想要的結果，展示如下：

%YAML:1.0
---
type: IMU
name: imu_davis346
Gyr:
   unit: " rad/s"
   avg-axis:
      gyr_n: 3.4207443164969696e-03
      gyr_w: 5.0328372766535944e-05
   x-axis:
      gyr_n: 2.8679837408646372e-03
      gyr_w: 5.2377301938209580e-05
   y-axis:
      gyr_n: 3.4204365908127145e-03
      gyr_w: 5.9820318994959333e-05
   z-axis:
      gyr_n: 3.9738126178135566e-03
      gyr_w: 3.8787497366438921e-05
Acc:
   unit: " m/s^2"
   avg-axis:
      acc_n: 4.0577448874376872e-02
      acc_w: 8.7349218314222493e-04
   x-axis:
      acc_n: 3.6370001351966601e-02
      acc_w: 9.6556492723349487e-04
   y-axis:
      acc_n: 3.4926548351679493e-02
      acc_w: 8.3124335009033201e-04
   z-axis:
      acc_n: 5.0435796919484514e-02
      acc_w: 8.2366827210284801e-04

撰寫imu.yaml，格式參考https://github.com/ethz-asl/kalibr/wiki/yaml-formats中的imu.yaml，具體引數使用之前imu標定得到的引數，示例如下：

#Accelerometers
accelerometer_noise_density: 4.0577448874376872e-02   #Noise density (continuous-time)
accelerometer_random_walk:   8.7349218314222493e-04   #Bias random walk

#Gyroscopes
gyroscope_noise_density:     3.4207443164969696e-03   #Noise density (continuous-time)
gyroscope_random_walk:       5.0328372766535944e-05   #Bias random walk

rostopic:                    /dvs/imu      #the IMU ROS topic
update_rate:                 1000.0      #Hz (for discretization of the values above)

若不加速播放rosbag得到的結果如下：

%YAML:1.0
---
type: IMU
name: imu_davis346
Gyr:
   unit: " rad/s"
   avg-axis:
      gyr_n: 3.4869979619824697e-03
      gyr_w: 4.4740603706140853e-05
   x-axis:
      gyr_n: 2.9539477648808021e-03
      gyr_w: 5.0580216740422281e-05
   y-axis:
      gyr_n: 3.5214141180930189e-03
      gyr_w: 5.4806050604838655e-05
   z-axis:
      gyr_n: 3.9856320029735878e-03
      gyr_w: 2.8835543773161611e-05
Acc:
   unit: " m/s^2"
   avg-axis:
      acc_n: 4.2153479580575477e-02
      acc_w: 8.5654389798364998e-04
   x-axis:
      acc_n: 3.7662088244236419e-02
      acc_w: 8.9242080034822346e-04
   y-axis:
      acc_n: 3.8469169601091632e-02
      acc_w: 8.9970652031743314e-04
   z-axis:
      acc_n: 5.0329180896398394e-02
      acc_w: 7.7750437328529356e-04

還是有點差別的～按這個來把～～～

camera標定

產生資料檔案也是用于聯合標定

1.標定板，可在kalibr的wiki中下載，地址：https://github.com/ethz-asl/kalibr/wiki/downloads

選擇

下載（然后發現根本下載不了，，，eth這群貨真的是，，，，event camera的驅動弄得崩潰，連標定的扳子也搞？？？）鏈接: 百度網盤請輸入提取碼提取碼: r4ts

然后縮放到40%，用A4紙就可以列印出來
原始pdf的格子引數是：
6*6的格子
大格子邊長：5.5cm
小格子邊長：1.65cm
小格子與大格子邊長比例：0.3
調整后的格子引數是：
大格子邊長：2.4cm
小格子邊長：0.75cm
小格子與大格子邊長比例：0.3125

但這只是理想情況，實際情況還得實際測量，
新建april_6x6_A4.yaml檔案，格式參考上圖的yaml，內容展示如下：

target_type: 'aprilgrid' #gridtype
tagCols: 6               #number of apriltags
tagRows: 6               #number of apriltags
tagSize: 0.024           #size of apriltag, edge to edge [m]
tagSpacing: 0.3125          #ratio of space between tags to tagSize

錄制bag，錄制bag 的同時，相機對準標定板，或是固定相機或是固定標定板，晃動另一個，動作不要太大，不要讓相機看不清標定板（就爭取把標定板晃動到過相機像素平面的每個地方）

注意：需要修改相機幀數（官方推薦是4Hz，盡管實際頻率不完全準確，但是不影響結果）
kalibr在處理標定資料的時候要求頻率不能太高，一般為4Hz，我們可以使用如下命令來更改topic的頻率，實際上是將原來的topic以新的頻率轉成新的topic，實際測驗infra1才是對應左目相機

roslaunch vins davis_testing.launch

rostopic list

rostopic hz /dvs/image_raw

rosrun topic_tools throttle messages /dvs/image_raw 4.0 /color


rostopic hz /color


roslaunch vins davis_raw_image_recording.launch

錄制的topic就是轉換頻率后的topic

rosbag play /home/kwanwaipang/dataset/gwphku/hku_davis346_image_raw_imu_2021-10-26-14-31-10.bag

然后就使用上面安裝好的Kalibr進行標定

source ~/kalibr_workspace/devel/setup.bash
kalibr_calibrate_cameras --target /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/april_6x6_A4.yaml --bag  /home/kwanwaipang/dataset/gwphku/hku_davis346_image_raw_imu_2021-10-26-14-31-10.bag --models pinhole-equi --topics /color --show-extraction

其中–target …/yaml/april_6x6_A4.yaml是標定板的組態檔，注意如果選擇棋格盤，注意targetCols和targetRows表示的是內側角點的數量，不是格子數量，–bag multicameras_calibration.bag是錄制的資料包，models pinhole-equi pinhole-equi pinhole-equi表示三個攝像頭的相機模型和畸變模型（解釋參考https://github.com/ethz-asl/kalibr/wiki/supported-models，根據需要選取）， --topics /infra_left /infra_right /color表示三個攝像頭對應的拍攝的資料話題，–bag-from-to 10 100表示處理bag中10-100秒的資料，–show-extraction表示顯示檢測特征點的程序，這些引數可以相應的調整，

kalibr_calibrate_cameras --target ../yaml/april_6x6_A4.yaml --bag  multicameras_calibration.bag --models pinhole-equi pinhole-equi pinhole-equi --topics /infra_left /infra_right /color --bag-from-to 10 100 --show-extraction

出來的標定結果如下圖所示

得到的結果如下所示

cam0:
  cam_overlaps: []
  camera_model: pinhole
  distortion_coeffs: [0.023761891762741624, -0.6457616668645434, 2.070114304159524,
    -2.4332476089446473]
  distortion_model: equidistant
  intrinsics: [333.6626192244177, 333.5395724565995, 162.74154656440015, 133.0594987830887]
  resolution: [346, 260]
  rostopic: /color

若改為降低速率前的topic效果如下：

source ~/kalibr_workspace/devel/setup.bash
kalibr_calibrate_cameras --target /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/april_6x6_A4.yaml --bag  /home/kwanwaipang/dataset/gwphku/hku_davis346_image_raw_imu_2021-10-26-14-31-10.bag --models pinhole-equi --topics /dvs/image_raw --show-extraction

cam0:
  cam_overlaps: []
  camera_model: pinhole
  distortion_coeffs: [0.007145831923439896, -0.4460587583609059, 1.2828141357453273,
    -1.3797467604219862]
  distortion_model: equidistant
  intrinsics: [333.649413082246, 333.5165283699802, 162.51929394284377, 132.6341713511583]
  resolution: [346, 260]
  rostopic: /dvs/image_raw

撰寫camchain.yaml，格式參考Kalibr官方教程https://github.com/ethz-asl/kalibr/wiki/yaml-formats中的chain.yaml，具體的引數參考上面得到的yaml檔案，沒有的引數可以洗掉，最終結果示例如下：

cam0:
  camera_model: pinhole
  intrinsics: [333.649413082246, 333.5165283699802, 162.51929394284377, 132.6341713511583]
  distortion_model: equidistant
  distortion_coeffs: [0.007145831923439896, -0.4460587583609059, 1.2828141357453273, -1.3797467604219862]
  T_cam_imu:
  - [0.01779318, 0.99967549,-0.01822936, 0.07008565]
  - [-0.9998017, 0.01795239, 0.00860714,-0.01771023]
  - [0.00893160, 0.01807260, 0.99979678, 0.00399246]
  - [0.0, 0.0, 0.0, 1.0]
  timeshift_cam_imu: -8.121e-05
  rostopic:  /dvs/image_raw
  resolution: [346, 260]

IMU與camera的聯合標定

將之前矯正好的檔案放好

source ~/kalibr_workspace/devel/setup.bash
kalibr_calibrate_imu_camera --bag [filename.bag] --cam [camchain.yaml] --imu [imu.yaml] --target [target.yaml] --bag-from-to 15 75 --show-extraction

kalibr_calibrate_imu_camera --bag /home/kwanwaipang/dataset/gwphku/hku_davis346_image_raw_imu_2021-10-26-14-31-10.bag --cam /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/camchain.yaml --imu /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/imu.yaml --target /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/april_6x6_A4.yaml --show-extraction

也有一種說法需要調整引數頻率

注意選擇的camera失真模型（https://github.com/ethz-asl/kalibr/wiki/supported-models）

roslaunch vins davis_testing.launch
rosrun topic_tools throttle messages /dvs/image_raw 20.0 /image_raw 
rosrun topic_tools throttle messages /dvs/imu 200.0 /imu
roslaunch vins davis_raw_image_imu_recording.launch 

source ~/kalibr_workspace/devel/setup.bash
kalibr_calibrate_cameras --target /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/april_6x6_A4.yaml --bag /home/kwanwaipang/dataset/gwphku/hku_davis346_image_imu_2021-10-26-16-14-23.bag --models pinhole-radtan --topics /image_raw --show-extraction

kalibr_calibrate_imu_camera --bag /home/kwanwaipang/dataset/gwphku/hku_davis346_image_imu_2021-10-26-16-14-23.bag --cam /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/camchain_second.yaml --imu /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/imu_second.yaml --target /home/kwanwaipang/catkin_ws_dvs/src/EVIO/config/kalibr_davis/april_6x6_A4.yaml --show-extraction

至此，矯正完成！測驗一下這些引數，

出來的pdf report如下

camera校正的report