aldaris's profile - activity

It seems that I can't comment under your answer. Thank you very much for you help. It works. It also helps me to better understand how nodes communicate with each other. I have never edit ROS wiki before, I will try later.

I'm a new user of Linux and ROS. I'm running the Groovy on Ubuntu 12.04. I meet some problems with the tutorials on roslaunch. Using the launch file turtlemimic.launch:

<launch>

<group ns="turtlesim1">
<node pkg="turtlesim" name="sim" type="turtlesim_node"/>
</group>

<group ns="turtlesim2">
<node pkg="turtlesim" name="sim" type="turtlesim_node"/>
</group>

<node pkg="turtlesim" name="mimic" type="mimic">
<remap from="input" to="turtlesim1/turtle1"/>
<remap from="output" to="turtlesim2/turtle1"/>
</node>

</launch>

After running the launch file, I can get two turtlesims started. Command

$ rostopic pub /turtlesim1/turtle1/command_velocity turtlesim/Velocity -r 1 --   2.0  -1.8

also allowed me to control the two turtles moving in circles. But after I ran the command

$ rosrun rqt_graph rqt_graph

the result shows as followed:

                 /turtlesim1/turtle1/pose         /turtlesim2/turtle1/command_velocity
/turtlesim1/sim --------------------------> /mimic--------------------> /turtlesim2/sim

This is different from the one in tutorials:

              /turtle1/command_velocity
 teleop_turtle-----------------------> 
              /turtle1/command_velocity  /turtlesim
 rostopic....------------------------>

I don't know whether it's the problem of my setting or not. The result I got makes more sense to me. I also tried to add several lines in the launch file:

  <node pkg="turtlesim" name="tele" type="turtle_teleop_key">
  <remap from="output" to="turtlesim1/turtle1"/>
  </node>

But I still can't control the turtle using keyboard. I checked the node information of "tele", the results are:

Node [/tele]
Publications: 
 * /rosout [rosgraph_msgs/Log]
* /turtle1/command_velocity [turtlesim/Velocity]

Subscriptions: None

Services: 
* /tele/get_loggers
* /tele/set_logger_level


contacting node htt p://localhost:36452/ ...
Pid: 9285
Connections:
* topic: /rosout
* to: /rosout
* direction: outbound
* transport: TCPROS

Can anyone tell me what's happening? Thanks in advance.

I killed the node /my_turtle and used $ rosrun turtlesim turtlesim_node __name:=other_name, unless I restarted the roscore, /my_turtle will still be in the list.

I'm running groovy on ubuntu 12.04.1. I'm new to ROS. When I was going through the tutorials on

w ww.ros.org/wiki/ROS/Tutorials/UnderstandingNodesTutorials/UnderstandingNodes

roscore worked as the tutorials describes. When I typed

$ rosrun turtlesim turtlesim_node __name:=my_turtle

two turtles showed up. I ran

$ rosnode list

and I got the following information:

/my_turtle
/rosout
/turtlesim

As noted in the tutorials, I shouldn't get the /turtlesim in the list. So I set the environment variables according to the page single machine configuration, I set

$ export ROS_HOSTNAME=localhost
$ export ROS_MASTER_URI=htt p://localhost:11311

and sourced the variables. The last few lines of my ~/.bashrc file are:

export ROS_HOSTNAME=localhost
export ROS_MASTER_URI=htt p://localhost:11311
source /opt/ros/groovy/setup.bash

I added a space in the URI, cos I'm not allowed to post link yet. I ran the codes again, but /turtlesim was still in the list. I ran roswtf after, and I got the following information:

No package or stack in context
================================================================================
Static checks summary:

No errors or warnings
================================================================================
Beginning tests of your ROS graph. These may take awhile...
analyzing graph...
... done analyzing graph
running graph rules...
... done running graph rules

Online checks summary:

Found 1 warning(s).
Warnings are things that may be just fine, but are sometimes at fault

WARNING The following node subscriptions are unconnected:
* /turtlesim:
* /turtle1/command_velocity
* /my_turtle:
* /turtle1/command_velocity


Found 1 error(s).

ERROR Communication with [/my_turtle] raised an error:

I searched here and didn't find similar questions, so what can I do to fix this problem? Thanks in advance.