sonictl's profile - activity

Ask about the usage of the tilde '~'sign

what's the difference between :

pub = rospy.Publisher('~cmd_vel', Twist, queue_size=5)

and:

pub = rospy.Publisher('cmd_vel', Twist, queue_size=5)

By the way, what's the queue_size in the bracket mean?

Thank you!!

Application: Save several pose and quaternion pairs into a file and load them to plan a navigation which has several intermediate stops.

Background: I'm developing nodes that can receive user's command and save current pose/quaternion data of robot into a file(e.g. yaml file or bag file) in an sequence. This is called task planning.

I will also make a node that can load that file and make the robot go to goals in sequence recorded in that file. This is called task replaying.

Question: Is there any tool/ros_package that I can use?

My plan now is using the yaml file and the yaml-library-for-python that can handle .yaml files. Also, rbbg mentioned the .bag file solution. Thank him~

Thank You!

ps: if there is any puzzles, feel free to ask me. :-)

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How to use rostopic pub to publish multiple line or \n or \r\r for std_msgs/String typed topic.

I tried as YAML commandLine said. but nothing works.

Thank you!!!

$ rostopic pub /send_BTSVR std_msgs/String ['test'] --- ['test2'] ---

Usage: rostopic pub /topic type [args...]

rostopic: error: no such option: ---

$ rostopic pub /send_BTSVR std_msgs/String ['test'] --- ['test2'] ---

Usage: rostopic pub /topic type [args...]

rostopic: error: no such option: ---

reference: http://wiki.ros.org/ROS/Tutorials/Usi...

I have a question: when 'roslaunch' launchs the turtlemimic.launch file, there appears two turtles' window. Why can I only use 'rostopic pub' command to drive the turtle1, however, I cannot use 'rosrun turtlesim turtle_teleop_key' command to do that. the instruction page: http://wiki.ros.org/ROS/Tutorials/Usi...

the 'rostopic pub' command: $ rostopic pub /turtlesim1/turtle1/cmd_vel geometry_msgs/Twist -r 1 -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, -1.8]'

the 'rosrun turtlesim turtle_teleop_key' command: $ rosrun turtlesim turtle_teleop_key

I met error when i use gmaping:

in rviz , i see the simulated position is 1/2 of the reality, when i was using gmapping + laser_scaner to build the map.

when I echo the topic /odom , it shows me the right value. is there experts tell me how to configure this?

please see the figure below:

Thank You Very Much!!

I refered the gmaping wiki page and met the tf requirements. I'm using ros_indigo.

my Question is: How to configure my gmapping or other things to make the /scan can be relative static with /map? so I can build reasonable map.

rospy.Time(0) 这是什么含义? 跟rospy.Time.now() 有啥区别？ Hi, I'm learning tf and time at this link

and I'm confused about the different between rospy.Time(0) and rospy.Time.now()

Could you explain it for me?

Thank you very much!!

how to set the turtlebot point or not point to a specific orientation when it arrives the goal?

I'm using rviz to set the goal for my mova_base for Turtlebot.

How to configure the amcl files or something others to make the turtlebot point or not point to the specific orientation when it arrives the goal.

Thanks!!