could not open port /dev/ttyACM0,but i use "sudo chmod 666/dev/ttyACM0“ ，“chmod: "666/dev/tty/ACM0" 后缺少操作数 Try 'chmod --help' for more information.”

edit

Straight dump of console output:

$ ROS_NAMESPACE=om_with_tb3 roslaunch turtlebot3_bringup turtlebot3_robot.launch multi_robot_name:=om_with_tb3 set_lidar_frame_id:=om_with_tb3/base_scan
... logging to /home/pi/.ros/log/b64e31c2-5472-11e9-828c-ace01033ad0f/roslaunch-raspberrypi-993.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://192.168.43.142:36451/

SUMMARY
========

PARAMETERS
 * /om_with_tb3/turtlebot3_core/baud: 115200
 * /om_with_tb3/turtlebot3_core/port: /dev/ttyACM0
 * /om_with_tb3/turtlebot3_core/tf_prefix: om_with_tb3
 * /om_with_tb3/turtlebot3_lds/frame_id: om_with_tb3/base_...
 * /om_with_tb3/turtlebot3_lds/port: /dev/ttyUSB0
 * /rosdistro: kinetic
 * /rosversion: 1.12.13

NODES
  /om_with_tb3/
    turtlebot3_core (rosserial_python/serial_node.py)
    turtlebot3_diagnostics (turtlebot3_bringup/turtlebot3_diagnostics)
    turtlebot3_lds (hls_lfcd_lds_driver/hlds_laser_publisher)

ROS_MASTER_URI=http://192.168.43.116:11311

process[om_with_tb3/turtlebot3_core-1]: started with pid [1002]
process[om_with_tb3/turtlebot3_lds-2]: started with pid [1003]
process[om_with_tb3/turtlebot3_diagnostics-3]: started with pid [1004]
[INFO] [1553909289.526154]: ROS Serial Python Node
[INFO] [1553909289.607560]: Connecting to /dev/ttyACM0 at 115200 baud
[ERROR] [1553909289.627768]: Error opening serial: [Errno 2] could not open port /dev/ttyACM0: [Errno 2] No such file or directory: '/dev/ttyACM0'
[om_with_tb3/turtlebot3_core-1] process has finished cleanly
log file: /home/pi/.ros/log/b64e31c2-5472-11e9-828c-ace01033ad0f/om_with_tb3-turtlebot3_core-1*.log
^C[om_with_tb3/turtlebot3_diagnostics-3] killing on exit
[om_with_tb3/turtlebot3_lds-2] killing on exit
shutting down processing monitor...
... shutting down processing monitor complete
done
Unhandled exception in thread started by 
sys.excepthook is missing
lost sys.stderr