Error when initializing trac_ik on Noetic

edit

I believe the error is coming due to an incorrect installation of trac_ik. To answer you completely, I tested it in ROS Noetic and found it working. Please see below:

1. Install trac_ik: Please install from pre-built binaries as shown below:

   $ sudo apt install ros-noetic-trac-ik
   

2. Install dependency to run an example: We do not need this package. But here, I want to run an example to confirm trac_ik.

   $ sudo apt install ros-noetic-pr2-description
   

3. Run example: The pr2_arm.launch uses TRAC_IK::TRAC_IK tracik_solver(chain_start, chain_end, urdf_param, timeout, eps)

   ravi@dell:~$ roslaunch trac_ik_examples pr2_arm.launch 
   ... logging to /home/ravi/.ros/log/a428d09e-64be-11ek-b98a-bhc0cd415369/roslaunch-dell-13219.log
   Checking log directory for disk usage. This may take a while.
   Press Ctrl-C to interrupt
   Done checking log file disk usage. Usage is <1GB.
   
   started roslaunch server http://dell:36633/
   
   SUMMARY
   ========
   
   PARAMETERS
    * /robot_description: <?xml version="1....
    * /rosdistro: noetic
    * /rosversion: 1.15.14
    * /trac_ik_tests/chain_end: r_wrist_roll_link
    * /trac_ik_tests/chain_start: torso_lift_link
    * /trac_ik_tests/num_samples: 1000
    * /trac_ik_tests/timeout: 0.005
    * /trac_ik_tests/urdf_param: /robot_description
   
   NODES
     /
       trac_ik_tests (trac_ik_examples/ik_tests)
   
   auto-starting new master
   process[master]: started with pid [13259]
   ROS_MASTER_URI=http://localhost:11311
   
   setting /run_id to a428d09e-64be-11ek-b98a-bhc0cd415369
   process[rosout-1]: started with pid [13284]
   started core service [/rosout]
   process[trac_ik_tests-2]: started with pid [13287]
   [ INFO] [1668500629.439007277]: Using 7 joints
   [ INFO] [1668500629.440011185]: *** Testing KDL with 1000 random samples
   [ INFO] [1668500629.440163447]: 0% done
   [ INFO] [1668500630.509473437]: 90% done
   [ INFO] [1668500630.632576062]: KDL found 859 solutions (85.9%) with an average of 0.0011914 secs per sample
   [ INFO] [1668500630.632594903]: *** Testing TRAC-IK with 1000 random samples
   [ INFO] [1668500630.632938700]: 0% done
   [ INFO] [1668500631.733434004]: TRAC-IK found 955 solutions (95.5%) with an average of 0.0010914 secs per sample
   [trac_ik_tests-2] process has finished cleanly
   log file: /home/ravi/.ros/log/a428d09e-64be-11ek-b98a-bhc0cd415369/trac_ik_tests-2*.log
   ^C[rosout-1] killing on exit
   [master] killing on exit
   shutting down processing monitor...
   ... shutting down processing monitor complete
   done
   

Note

Please read below if you get the following error with pr2_arm.launch file

RLException: Invalid <param> tag: Cannot load command parameter [robot_description]: no such command [['/opt/ros/noetic/share/xacro/xacro.py', '/opt/ros/noetic/share/pr2_description/robots/pr2.urdf.xacro']]. 

Param xml is <param name="robot_description" command="$(find xacro)/xacro.py '$(find pr2_description)/robots/pr2.urdf.xacro'"/>
The traceback for the exception was written to the log file

Please change xacro.py to xacro at line#8 of /opt/ros/noetic/share/trac_ik_examples/launch/pr2_arm.launch file as suggested here.

Update

With "chain_start", "chain_end", as "base_link", and "tool0" respectively, the IK test of kuka lbr iiwa robot using trac_ik works smoothly. Below is the kuka_lbr_iiwa.launch file:

<?xml version="1.0"?>
<launch>
  <arg name="num_samples" default="1000" />
  <arg name="chain_start" default="base_link" />
  <arg name="chain_end" default="tool0" />
  <arg name="timeout" default="0.005" />

  <param name="robot_description" command="$(find xacro)/xacro --inorder '$(find kuka_lbr_iiwa_support)/urdf/lbr_iiwa_14_r820.xacro'" />

  <node name="trac_ik_tests" pkg="trac_ik_examples" type="ik_tests" output="screen">
    <param name="num_samples" value="$(arg num_samples)" />
    <param name="chain_start" value="$(arg chain_start)" />
    <param name="chain_end" value="$(arg chain_end ...