利用Kalibr标定双目相机与IMU

技术2022-07-13 74

本文介绍如何利用Kalibr标定工具进行双目相机与IMU的联合标定。主要过程包括以下四步：

生成标定板标定双目相机标定IMU联合标定

1. 生成标定板

使用AprilTag

rosrun kalibr kalibr_create_target_pdf --type apriltag --nx 6 --ny 6 --tsize 0.002 --tspace 0.3

遇到问题"ImportError: No module named pyx" 玄学解法：

sudo apt-get install python-pyx

2. 标定双目相机

降低帧率

rosrun topic_tools throttle messages /l_cam/image_raw 4 /left rosrun topic_tools throttle messages /r_cam/image_raw 4 /right advertised as /left //出现时说明将帧成功

录制bag包

rosbag record /left /right >mycamera.bag

遇到的错误

ImportError: cannot import name NavigationToolbar2Wx

/home/cjn/kalibr/src/kalibr/Schweizer-Messer/sm_python/python/sm/PlotCollection.py

解决方法：将 PlotCollection.py 中的NavigationToolbar2Wx 改为 NavigationToolbar2WxAgg

ImportError: No module named igraph

sudo apt-get install python2.7-igraph

kalibr标定时出现：ImportError: No module named Image.

解决方法：在kalibr_workspace/aslam_offline_calibration/kalibr/python/kalibr_camera_calibration/MulticamGraph.py中将import Image改为from PIL import Image

rosrun kalibr kalibr_calibrate_cameras --bag '/home/guoben/stereocam.bag' --topics /left /right --models pinhole-radtan pinhole-radtan --target '/home/guoben/Project/Kalibr_ws/april_6x6_80x80cm.yaml' --show-extraction --approx-sync 0.1

注意事项：

标定的时候图中不能存在两个标定板起始画面和终止画面要稳定

3. 标定IMU

参考：IMU噪声标定——加速度计和陀螺仪的白噪声和零偏不稳定性

//录制bag文件

collect the data while the IMU is Stationary, with a two hours duration; rosbag record /imu0

有Code_utils和imu_utils两个包先编译code_utils再编译imu_tils

得到的imu.yaml

type: IMU name: ICM20602 Gyr: unit: " rad/s" avg-axis: gyr_n: 1.4127871720120859e+02 gyr_w: 4.8477797168896648e-03 x-axis: gyr_n: 3.9615886574940606e+02 gyr_w: 4.8477797168896648e-03 y-axis: gyr_n: 1.5284722859858114e+01 gyr_w: 4.8477797168896648e-03 z-axis: gyr_n: 1.2392562994361640e+01 gyr_w: 4.8477797168896648e-03 Acc: unit: " m/s^2" avg-axis: acc_n: 3.8264508828802807e-01 acc_w: 1.0613073078261251e-02 x-axis: acc_n: 3.6962189636668691e-01 acc_w: 1.0916554449621266e-02 y-axis: acc_n: 4.6707198750779616e-01 acc_w: 1.0721472803944067e-02 z-axis: acc_n: 3.1124138098960102e-01 acc_w: 1.0201191981218414e-02

修改为如下样式：

rostopic: /imu0 update_rate: 100.0 #Hz accelerometer_noise_density: 3.8264508828802807e-01 #continous accelerometer_random_walk: 1.0613073078261251e-02 gyroscope_noise_density: 1.4127871720120859e+02 #continous gyroscope_random_walk: 4.8477797168896648e-03

4. 录制数据包

沿着3个轴旋转平移三次

5. 联合标定

准备好四个文件

标定半文件相机参数文件imu参数文件数据bag文件 rosrun kalibr kalibr_calibrate_imu_camera --target april_6x6_80x80cm.yaml --cam stereocam.yaml --imu ICM20602.yaml --bag camera_imu.bag --timeoffset-padding 0.1

6. 标定结果

得到结果为camchain.yaml

cam0: T_cam_imu: # 从IMU到相机坐标的转换 - [0.08233179976406399, -0.9949127683235393, -0.05805220214946505, -0.008744023342066004] - [-0.9959106050536686, -0.08430878258416843, 0.032466843406961834, 0.07000917129335886] - [-0.03719598754229868, 0.055141750117018384, -0.9977854708827878, -0.11902680705823296] - [0.0, 0.0, 0.0, 1.0] cam_overlaps: [1] camera_model: pinhole distortion_coeffs: [-0.4274960254764774, 0.1522753401860188, 0.022086313718892994, -0.0007250205609533983] #失真模型的参数向量 distortion_model: radtan intrinsics: [576.2948258096362, 570.5120047531799, 290.9276492936449, 165.99488000803987] #相机内参之前标好的 resolution: [640, 480] #分辨率 rostopic: /l_cam/image_raw #话题 timeshift_cam_imu: -0.04319840825131607 #漂移 cam1: T_cam_imu: # 从IMU到相机坐标的转换 - [0.0894795247331801, -0.9911722483784674, 0.0978314300104943, -0.06676213145949367] - [-0.995095690056223, -0.08480851440432002, 0.05091250844401363, 0.06960856622513922] - [-0.04216612722380045, -0.10190726141402426, -0.9938998580269747, -0.12389393733183268] - [0.0, 0.0, 0.0, 1.0] T_cn_cnm1: - [0.9878176058814627, -0.002372804306504643, -0.1555980311904324, -0.07647885002996721] - [-0.000506528488511444, 0.9998294218114983, -0.01846268422998622, -0.0025906464811484946] - [0.155615297896788, 0.018316579369764666, 0.9876479038507021, -0.0062589855841411746] - [0.0, 0.0, 0.0, 1.0] cam_overlaps: [0] camera_model: pinhole distortion_coeffs: [-0.4358292770104687, 0.13856343257725542, 0.01867787729653694, -0.011189753016360725] distortion_model: radtan intrinsics: [572.0873971077864, 571.5888157262697, 349.04660762135626, 174.35778659111406] resolution: [640, 480] rostopic: /r_cam/image_raw timeshift_cam_imu: -0.002440062477866302

7. 使用Kalibr进行单目相机与IMU的联合标定

出现问题：

Spline Coefficient Buffer Exceeded. Set larger buffer margins”

在标定命令最后添加 --timeoffset-padding 0.1

timeoffset-padding这个参数可以适当的设置的大一些

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