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2014-01-30 06:19:21 -0600 asked a question Adding ros integrated contact sensors

Hello everyone!

I'm building a biped model and I want to add a sensor that detects a collision between its foot and the ground and sends a message to a ROS topic.

The 'Bumper controller' described here sounds pretty much like what I want. But when I try to put the following tag in the .gazebo file:

  <plugin name="gazebo_ros_bumper_controller" filename="">

As suggested in the tutorial, I get the following error:

Error [] Model[bumperbot] is attempting to load a plugin, but detected an incorrect plugin type. Plugin filename[] name[gazeborosbumpercontroller]

I ftought it was because I did not specify any link for the sensor, so I tried using:

<gazebo reference='base_link'>

This time I got the message:

Error [] XML Element[plugin], child of element[link] not defined in SDF. Ignoring.[link]
Error [] Error reading element <link>
Error [] Error reading element <model>
Error [] Unable to read element <sdf>
Error [] parse as old deprecated model file failed.
Error [] Unable to read sdf string

I also tried to follow this answer, which suggested using a tag like this:

<sensor:contact name="contact_sensor">
  <controller:gazebo_ros_bumper name="gazebo_ros_bumper_controller" plugin="">
      <interface:bumper name="bumper_iface" />

This time the xml couldn't even be parsed.

I did manage to add the gazebo contact sensor

<gazebo reference="base_link">
  <sensor type="contact" name="contact">
    <plugin name='gazebo_contact' filename=''/>

But it publishes to a gazebo topic, not a ROS topic.

Does anyone know what am I doing wrong? I'm using gazebo 1.9.3 and ros-hydro.

P.S: I've noticed the turtlebot has a sensor that does exactly what I want, but I couldn't figure out where to find the plugin which is used there or how to add it to my model.

Thanks in advance!

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2013-03-12 09:17:09 -0600 asked a question Physics solver parameters and BDI behavior controller

I just installed the latest DRCSim (had to compile from source because although Gazebo 1.5 was added to the repository, DRCSim 2.2 wasn't). As we work mainly on getting the robot to walk, the first thing we tried is the BDI behavior controller which produces a fine walking gait. It was clear from the tutorial that this runs with different solver parameters so we got curious about what happens with normal parameters and found out that a small change in any of the parameters will cause the controller to fail (the robot joints don't behave as expected causing the robot to fall). The question is: what will the solver parameters be during the qualifications and the VRC? Which approach would you recommend for developing a walking algorithm if the behavior changes so drastically depending on the solver parameters?

2013-03-12 08:39:33 -0600 commented answer Is it possible to control the GUI camera with python to follow a model?

Great! It would be very useful to have such a feature

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2013-03-07 03:00:00 -0600 asked a question Is it possible to control the GUI camera with python to follow a model?

Using the current Gazebo GUI it is possible to focus the camera on any model using the "Move To" option. However, the camera doesn't "attach" to the model, i.e. the camera doesn't follow the model once it moves. Is there a way of calling "Move To" from python or calling some service that moves the camera so it will track the model automatically?

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2013-02-06 09:21:43 -0600 answered a question DRCsim 2.0 problem with effort control and /joint_commands topic

UPDATE: found the cause for the second problem, apparently the messages were sent with no time stamp so rxplot couldn't plot them, so now I set the time stamp of the joint_commands message manually before sending and it works fine (I thought it was done automatically by the publisher)

the first problem still stands though.

2013-02-05 15:41:04 -0600 asked a question DRCsim 2.0 problem with effort control and /joint_commands topic

Hello, I updated to drcsim 2.0 and i'm having problems controlling the joint effort. as suggested in the user guide I send a message to /atlas/joint_commands with the desires efforts, and PID gains set to 0, the torques I'm getting look nothing like the command I give, first the amplitude never seem to rise above 0.5 Nm (, second there seems to be a huge delay (a second or so) between reference and output signal, could someone please elaborate on how the effort control is modeled in DRCsim? are there any controller dynamics I'm not aware of? In the previous versions it seemed as if commanded effort would go directly to torques in gazebo

another problem I'm having is plotting the commanded effort with rxplot. in order to compare the command to the output I want to plot them side by side. whenever I try plotting the command($rxplot /atlas/jointcommands/effort[17]) the plot appears but only the 1st value appears, after that the time axis start getting negative values (?!) and the plotting area stays clear, to work around this issue I send the same message to command topic and to /testtopic, plotting /test_topic seems to work just fine, any idea why rxplot is having problems with that particular topic?

thanks in advance.

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2012-12-11 05:15:28 -0600 asked a question DRCSIM: gazebo crashes when model launced as "pinned"

I'm using the drc simulator and I've recently updated to gazebo 1.3, since then I encounter the following problem:

If I try to "pin" the robot model too early (publish "pinned" to /mode either from the launch file or from the command line) gazebo crashes. If I wait a little before I publish the message everything seems to work fine.

I also noticed that even though I launch my model with no position controllers started it still stays in a stiff position for several seconds before it collapses, perhaps this is the time when a pin command will crash the simulator?

Any idea what might be the problem?