Sietse's profile - activity

Hello all,

since a week or so, starting roscore doesn't work normally om my machine. The program hangs most of the time, there is nothing more than the command I entered. It only starts if I Ctrl-C the hanging roscore, then it suddenly starts. Very strange.

If I, e.g., start rviz it has the same behaviour (often), it only really starts when I ctrl-C the hanging program.

There were no ros-updates in the last month I think. I am running ubuntu 14.04 and indigo, all standard.

What can we wrong here? Thanks in advance,

Sietse

Hello List,

I am working with different ros versions, mostly kinetic and melodic. But my question pertains to all versions. Often it is difficult to stop ros programs, typing control-C often is not enough. It has to be repeated multiple times, it also take a long time to actually react. I usually ends with "excalating to SIGTERM" or something. I currently see this with gazebo_ros launch files.

Why is this so, what is the technical reason that a more clean and faster stop does not seem to be possible?

Regards, Sietse

Hello list,

Trying to get a trajectory controller working, but am unable to get a working action client. As a first test I tried to add it to the rrbot example from gazebo_ros_demos. As the rrbot_control.yaml I use the following:

 rrbot:
  # Publish all joint states -----------------------------------
  joint_state_controller:
    type: joint_state_controller/JointStateController
    publish_rate: 50  

  # Trajectory Controller  (not together with the position controllers)
  joint_trajectory_controller:
    type: effort_controllers/JointTrajectoryController
    joints:
      - joint1
      - joint2
    constraints:
      goal_time: 0.0
      stopped_velocity_tolerance: 0.01
      joint1: {trajectory: 0.01, goal: 0.01}
      joint2: {trajectory: 0.01, goal: 0.01}
    gains:
      joint1: {p: 100.0, d: 75.0, i: 0.0, i_clamp: 0.0}
      joint2: {p: 100.0, d: 25.0, i: 0.0, i_clamp: 0.0}
      state_publish_rate:  100
      action_monitor_rate: 100
      stop_trajectory_duration: 0.0

With an properly adapted launch file both controllers are loaded and started. All is well I think, but I have a problem creating a simple actionclient to use them. I actually do not know how to start the client (in Python). The client starts but noting happens, if keeps waiting for the server. The relevant line (i think) in my client is:

arm_client = actionlib.SimpleActionClient('rrbot/joint_trajectory_controller', FollowJointTrajectoryAction)

The first parameter is wrong, but what should it be? Is there an additional parameter needed in the yaml file?

Thanks in advance, Sietse

PS. Using melodic (from source) on debian test

No, I currently use ROS only on Ubuntu, and wait until ROS for newer versions will become available on Debian.

Hello List,

Creating simulation of a rower in a boat using ros, gazebo and trac_ik. There are three kinematic loops in the robot's description. This cannot be described in URDF, so they should be closed when generating the SDF from it. I use ik_fast to find the correct joint values for this. I created stubs on both sides of the, still, broken arm's, and ask trac_ik how to close them.

The project can be found om my github page. The code resides in the boot3_description directory. Please see this screenshot of the rower in rviz. The loop with the left arm is closed, but the right arm not yet. Also note the stub-links that have to be placed on top of each other.

I create a program ik_1.py that uses the joint state controller and trac_ik to calculate the correct values of the arm joints to close the loop. The new initial joint values are written in param.xacro to be used later.

Now my question. The program works perfectly when closing the left arm, but does NOT yield the proper values for the right arm. trac_ik finds a solution, but when the new values are used the right arm is not connected.

I can't find any difference in the two chains, apart of course of the different values to get another arm. How can trac_ik find a solution that is clearly wrong?

Hopefully someone can shed some light on this.

UPDATE: I was confused, I use trac_ik, not ik_fast.

Thanks in advance, Sietse

Answering my own question. There where some differences in the arms in orientation, and how axes where set, that got me

Oops, you are right. Thanks, Updated.

Closing kinematic loop with ik_fast Hello List, Creating simulation of a rower in a boat using ros, gazebo and trac_ik.

Closing kinematic loop with ik_fast Hello List, Creating simulation of a rower in a boat using ros, gazebo and trac_ik.

Closing kinematic loop with ik_fast Hello List, Creating simulation of a rower in a boat using ros, gazebo and ik_fast.

Track_IK is not designed to be used is less than 2 (controllable) joints. It normally gives an error about that, but is

Hello list,

After loading a simple urdf in the parameter server using the following launch file:

<launch>
  <param name="robot_description"
    command="xacro '$(find tf_if_test)/urdf/boot.xacro' " />

  <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher">
    <param name="use_gui" value="true"/>
  </node>

  <node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher"/>
  <node name="rviz" pkg="rviz" type="rviz" args="-d $(find tf_if_test/launch/boot.rviz"/>
</launch>

This works fine, but if I try to use trac_ik_python, but it fails with the following error:

terminate called after throwing an instance of 'ros::TimeNotInitializedException'
  what():  Cannot use ros::Time::now() before the first NodeHandle has been created or ros::start() has been called.  If this is a standalone app or test that just uses ros::Time and does not communicate over ROS, you may also call ros::Time::init()
Aborted (core dumped)

The code:

#!/usr/bin/env python                                                                                                       
import rospy
from trac_ik_python.trac_ik import IK

rospy.init_node('tester', anonymous=True)
ik_solver = IK("l1",               "l3")
print 'done'

I thought that init_node did the ros::start() here. Am I doing something wrong?

EDIT: Or is it a problem that there are only 2DOF in this robot?

2nd EDIT: I tried the patch by adding the ros::Timer::init() in the swig-file. That works. Then I removed that patched version of trac_ik completely and reverted to the official one. Now the problem does NOT return, It is really reverted, I also rebooted the machine. Weird....

Thanks in advance, Sietse

I will answer my own question. The error occurs here when the chain does NOT at least have 2 non-fixed joints in it. I'

Yes, I tried that, but it had no influence at all.

trac_ik fails on melodic Hello list, After loading a simple urdf in the parameter server using the following launch fil

I only tested on Melodic. Probably shouldn't have mentioned it. The problem now seems to have gone away, weird. See my e

trac_ik fails on melodic Hello list, After loading a simple urdf in the parameter server using the following launch fil

trac_ik fails on melodic Hello list, After loading a simple urdf in the parameter server using the following launch fil

Yes, looks like a duplicate. Only a bit weird that it did work a few months ago with an earlier version of testing.

Installing melodic on debian buster Hello list! Trying to install melodic using the recipe from http://wiki.ros.org/mel

Installing melodic on debian buster Hello list! Trying to install melodic using the recipe from http://wiki.ros.org/mel

simpleactionclient send_goal_and_wait problem Hello list, SECOND EDIT: I still am at a loss why the send_goal_and_wait

simpleactionclient send_goal_and_wait problem Hello list, SECOND EDIT: I still am at a loss why the send_goal_and_wait

simpleactionclient send_goal_and_wait problem Hello list, SECOND EDIT: I still am at a loss why the `send_goal_and_wai

Same here, probably because of an upgrade to libboost 1.67. At least here on debian testing, on which it worked fine wit

simpleactionclient send_goal_and_wait problem Hello list, Trying to send multiple trajectories to a robot simulated in

Thanks, see my edit above.

simpleactionclient send_goal_and_wait problem Hello list, Trying to send multiple trajectories to a robot simulated in