D435i IMU Calibration

# for nvidia jetson
$ cd ~/librealsense/tools/rs-imu-calibration
$ python3 rs-imu-calibration.py

# for desktop
1. Download this file
https://github.com/IntelRealSense/librealsense/blob/master/tools/rs-imu-calibration/rs-imu-calibration.py
2. Run python script
$ python3 rs-imu-calibration.py

• Command Line Parameters

Flag	Description	Default
-h	Show help.
-i <accel_filename> [gyro_filename]	Load previously saved results to EEPROM
-s serial_no	calibrate device with given serial_no	calibrate first found device
-g	show graph of data before and after calibration

Install Kalibr

$ mkdir kalibr_ws && cd kalibr_ws && mkdir src && cd src
$ sudo apt install libv4l-dev python-igraph
$ git clone https://github.com/ethz-asl/kalibr
$ cd .. && catkin build

# Type in ~/.bashrc
alias ks='source ~/kalibr_ws/devel/setup.bash'

# And git clone this repository

Stereo Camera calibration

$ roslaunch realsense2_camera rs_camera.launch
$ rosrun topic_tools throttle messages /camera/infra1/image_rect_raw 4.0 /left
$ rosrun topic_tools throttle messages /camera/infra2/image_rect_raw 4.0 /right
$ rosbag record -O stereo_calibra_d435i.bag /left /right

# set target and run (If the target board size is A4, change april_6x6_80x80cm.yaml to april_6x6_A4.yaml)
$ cd ~/kalibr_d435i/kalibr_calibrate_cameras
$ rosrun kalibr kalibr_calibrate_cameras --bag ~/kalibr_d435i/calibrate_cameras/stereo_calibra_d435i.bag --topics /left /right --models pinhole-radtan pinhole-radtan --target ~/kalibr_d435i/april_6x6_80x80cm.yaml --show-extraction

# if an error occurs: "Cameras are not connected through mutual observations, ....."
Add option: --approx-sync 0.04

Get noise density and bias random walk through imu_utils package

• Preparation and Collection

1. Install required libary
$ sudo apt install libdw-dev libgoogle-glog-dev libatlas-base-dev

2. Install package in ~/calib_ws/src
$ git clone https://github.com/gaowenliang/code_utils.git
$ cd .. && catkin build code_utils
$ cd src && git clone https://github.com/gaowenliang/imu_utils.git
$ cd .. && catkin build imu_utils

3. Move imu_utils_d435i.launch to imu_utils launch dir and start launch file
$ roslaunch imu_utils imu_utils_d435i.launch

4. Collect the data while the IMU is Stationary, with set duration time

• Create imu_d435i.yaml file with results
  • result

  type : IMU
  name : d435i
  Gyr :
  unit : "rad/s".
  avg-axis :
      gyr_n : 3.0247286551398204e-03
      gyr_w : 2.2901170839457266e-05
  x-axis :
      gyr_n : 3.0486121293259861e-03
      gyr_w : 2.3588043857742811e-05
  y-axis :
      gyr_n : 3.9906956275203298e-03
      gyr_w : 3.8510954801834231e-05
  z-axis :
      gyr_n : 2.0348782085731448e-03
      gyr_w : 6.6045138587947500e-06
  Acc :
  unit : "m/s^2".
  avg-axis :
      acc_n : 2.8949600741350223e-02
      acc_w : 4.5552273079824281e-04
  x-axis :
      acc_n : 2.4870413946165581e-02
      acc_w : 3.5175805157083910e-04
  y-axis :
      acc_n : 2.7808521377206314e-02
      acc_w : 4.8805723243924246e-04
  z-axis :
      acc_n : 3.4169866900678782e-02
      acc_w : 5.2675290838464703e-04
  

  • Create imu_d435i.yaml using the results above

  rostopic: /camera/imu
  update_rate: 200.0 # Hz
  
  accelerometer_noise_density: 2.89e-01
  accelerometer_random_walk: 4.55e-04 
  gyroscope_noise_density: 3.02e-03
  gyroscope_random_walk: 2.29e-05
  

Camera-IMU calibration

$ cd ~/kalibr_d435i/calibrate_imu_camera

# If the target board size is A4, change april_6x6_80x80cm.yaml to april_6x6_A4.yaml

## Method1
$ rosbag record -O stereo_imu_calibra_d435i.bag /camera/infra1/image_rect_raw /camera/infra2/image_rect_raw /camera/imu
$ rosrun kalibr_calibrate_imu_camera --target ~/kalibr_d435i/april_6x6_80x80cm.yaml --cam ~/kalibr_d435i/calibrate_cameras/calibra_d435i.yaml --imu ~/kalibr_d435i/calibrate_imu_camera/imu_d435i.yaml --bag ~/kalibr_d435i/calibrate_imu_camera/stereo_imu_calibra_d435i.bag

# Method2 (better??)
$ rosrun topic_tools throttle messages /camera/infra1/image_rect_raw 20.0 /left
$ rosrun topic_tools throttle messages /camera/infra2/image_rect_raw 20.0 /right
$ rosrun topic_tools throttle messages /camera/imu 200.0 /imu
$ rosbag record -O imu_stereo_d435i_20_200hz.bag  /left /right /imu
#### change rostopic value of imu_d435i.yaml to /imu
$ rosrun kalibr_calibrate_imu_camera --target ~/kalibr_d435i/april_6x6_80x80cm.yaml --cam ~/kalibr_d435i/calibrate_cameras/calibra_d435i.yaml --imu ~/kalibr_d435i/calibrate_imu_camera/imu_d435i.yaml --bag ~/kalibr_d435i/calibrate_imu_camera/imu_stereo_d435i_20_200hz.bag

Make VINS-Fusion config file

• camchain-imucam.yaml

d435i_stereo_imu.yaml	camchain-imucam.yaml	d435i_imu_param.yaml
body_T_cam0	cam0:T_cam_imu
body_T_cam1	cam1:T_cam_imu
acc_n		acc_n
gyr_n		gyr_n
acc_w		acc_w
gyr_w		gyr_w

• left.yaml, right.yaml

left.yaml & right.yaml	d435i_imu_param.yaml
distortion_parameters	distortion_coeffs
projection_parameters	intrinsics

Run VINS-Fusion

$ roslaunch realsense2_camera rs_camera.launch
$ roslaunch vins vins_rviz.launch
$ rosrun vins vins_node ~/kalibr_d435i/calibrate_imu_camera/vins_config/d435i_stereo_imu.yaml 
$ rosrun loop_fusion loop_fusion_node ~/kalibr_d435i/calibrate_imu_camera/vins_config/d435i_stereo_imu.yaml