Stage

http://www.ros.org/wiki/stage

move_base_stage Tutorial

Following the tutorial of amazing ROS in: http://www.ros.org/wiki/move_base_stage/Tutorials/stage%20and%20navigation%20stack

...

Well trying the tutorial everything went fine until I followed the step #5. At the last command I recieved an error message like this:



So I went to the .cc code and found the part of the code where that error message was generated:



I coulnd't find where actually the error was, so I decided to change the !=4 to !=3 and see what happens...

After making stage I ran the willow.world once again...

It didn't work, I changed the values first and then the message and it didn't change, I also rosmake stage and nothing... It seems to bee usign another code, because in all the extension of the model.cc there is no other message like that, I also might be reading a copy of that code in another part... so I will follow all the instructions again and see if it works well...
---
roscp is a useful commandline tool for copying files from one package to another.
pr2 throws a robot on map =D

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map_server
Provides the map_server ROS Node, which offers map data as a ROS Service. It also provides the map_saver command-line utility, which allows dynamically generated maps to be saved to file.
Maps manipulated by the the tools in this package are stored in a pair of files. The YAML file describes the map meta-data, and names the image file. The image file encodes the occupancy data.

http://www.ros.org/wiki/map_server
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Other resources:

Navigator Stack and Stage:
Simple tutorial that sets up navigation stack and rosstage. Can be used by any new beginner just to see how awesome and simple ROS is

To test navigation stack with both robots.

After the new actualization of the "To simulate two robots" ticket I need to run two robots in two maps. The commands I need to follow are these:

$ roscd simulator_stage
$ svn co `roslocate svn navigation_stage`
$ roslaunch navigation_stage move_base_multi_robot.launch

First of all I will check how does the twoRobots world run.

I think the problem might be around here:
oscar@oscar-laptop:/opt/ros/cturtle/stacks/sscrovers-ros-pkg$ rostopic echo robot_footprint

WARNING: topic [/robot_footprint] does not appear to be published yet

Because robot_footprint

robot_footprint (geometry_msgs/Polygon)

* Polygonal "footprint" around the robot. Rendered as a line.

I don't see any robot nor form on the map, and I should see it even in a corner of it.



I decided to try another example, in this case one using the same fake_localization node. I tried the move_base_fake_localization_10cm.launch example. But I had the the same problem. Then I decided to echo the different topics and see their messages, and I saw that many topics didn't publish anything, and the /odom topic published origin values.

After trying many ways to find the issue I decided to write a letter to the ROS community as follows:

HI everybody,

Im trying to run the launch/move_base_multi_robot.launch example launch file, it simulates two robots on different windows. But when the windows of nav_view opens I don't see anything but the map (image 1). Neither the inflated obstacles nor the particle cloud or the robot footprint seem to appear. I also looked for information in what was being published over those topics but there weren't any messages. I also receive a warning message when I run the launch file but I don't know if it has anything to do with it (Image 2):

[ WARN] [1285694547.646811796, 3.800000000]: The base_scan observation buffer has not been updated for 2.10 seconds, and it should be updated every 0.40 seconds.

This problem occurs also with the move_base_fake_localization_10cm.launch example, but in this case it opens a window from stage (Stage-3.2.2) and from there I can see the footprint of the robot (image 3). Also when I listen to the /odom topic (rostopic echo /odom) It prints the following (image 4):

wist:
twist:
linear:
x: 0.0
y: 0.0
z: 0.0
angular:
x: 0.0
y: 0.0
z: 0.0
covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

Could you please tell me the possible reason of why I cant see the footprints of the robot or anything else besides the map on the nav_view window?

The Version of Ubuntu I use is 10.4
The Version of ROS is CTurtle.
The Version of Stage is 3.2.2.

Image 1:


Image 2:


Image 3:


Image 4:


........
Chatting with Renato:

We saw that a a part of the launch file code is responsible of why in the multi robot example we don't see any stage map. When the stage node is declared there is a part where...

and if you delete it you can see now the stage map.

Actually when you set the goal on the nav_view map, the respective robot starts to move.

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Finally I could solve the problem by editing the rgb.txt file. Now both maps have their respective robots, and no important error seems to make problems on the simulation.

--
Oscar Rodrigo Hernández Panczenko IMT

Resources:

.pgm format: http://netpbm.sourceforge.net/doc/pgm.html

To see an image in terminal go to the directory where that image is and cast oeg:
http://netpbm.sourceforge.net/doc/pgm.html

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To see images cast eog "file"
To see pdf files cast xpdf "file"
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/rosout (roslib/Log)

* Standard ROS topic for publishing logging messages.
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/clock Topic

Nodes are automatically subscribed to the /clock Topic, which is a global Topic published by a Clock Server. The Clock Server publishes regular time Messages (at an unspecified rate).
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nav_view
Is a GUI for visualizing 2-D navigation. It is a specialized interface for the navigation stack.

nav_view displays:

* A map
* A robot's pose
* A cloud of particles (e.g., from a localization system)
* Two paths (e.g., from a path planner)
* A set of obstacles (and inflated obstacles)

http://www.ros.org/wiki/nav_view

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fake_localization:

The fake_localization package provides a single node, fake_localization, which substitutes for a localization system, providing a subset of the ROS API used by amcl. This node is most frequently used during simulation as a method to provide perfect localization in a computationally inexpensive manner.

Specifically, fake_localization converts odometry data into pose, particle cloud, and transform data of the form published by amcl.

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amcl:

amcl is a probabilistic localization system for a robot moving in 2D. It implements the adaptive (or KLD-sampling) Monte Carlo localization approach (as described by Dieter Fox), which uses a particle filter to track the pose of a robot against a known map.

http://www.ros.org/wiki/amcl

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map_server

map_server provides the map_server ROS Node, which offers map data as a ROS Service. It also provides the map_saver command-line utility, which allows dynamically generated maps to be saved to file.

http://www.ros.org/wiki/map_server

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cmd_vel:

cmd_vel geometry_msgs/Twist

* velocity commands to differentially drive the position model of the robot

http://www.ros.org/wiki/stage

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navigation_stage

This package holds example launch files for running the ROS navigation stack in stage.

http://www.ros.org/wiki/navigation_stage

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Information about some topics involved: