想做物体或者人脸识别，安装usb-cam运行后报错，查看实时图像时显示不出usb-cam的图像

熊猫panda

安装了usb-cam，但是运行roslaunch robot_vision usb_cam.launch 后报错


[ INFO] [1740536955.740403271]: using default calibration URL
[ INFO] [1740536955.741620887]: camera calibration URL: file:///home/hawkbot/.ros/camera_info/head_camera.yaml
[ INFO] [1740536955.741807514]: Unable to open camera calibration file [/home/hawkbot/.ros/camera_info/head_camera.yaml]
[ WARN] [1740536955.741835188]: Camera calibration file /home/hawkbot/.ros/camera_info/head_camera.yaml not found.
[ INFO] [1740536955.741860610]: Starting 'head_camera' (/dev/video0) at 640x480 via mmap (yuyv) at 30 FPS
[ERROR] [1740536955.741987453]: Cannot identify '/dev/video0': 2, No such file or directory
[usb_cam-1] process has died [pid 6827, exit code 1, cmd /opt/ros/noetic/lib/usb_cam/usb_cam_node __name:=usb_cam __log:=/home/hawkbot/.ros/log/52c00708-f3e9-11ef-ba4e-c589a1116ef5/usb_cam-1.log].
log file: /home/hawkbot/.ros/log/52c00708-f3e9-11ef-ba4e-c589a1116ef5/usb_cam-1*.log

hawkbot

最新的小车默认就自带相机，会发布相应话题，如果是老的使用树莓派的小车，请先检查树莓派是否识别到了usb相机，然后检查/dev/video0是否存在