How to load a controller from control_manager?

Question

Dears all,

I'm new to ROS_control and I'm investigating the possibility to use it to build an hardware-interface and a controller for a 6 gdl human-exoskeleton. To begin, I wrote a simple hardware-interface as the one in: https://github.com/ros-controls/ros_control/wiki/hardware_interface
I registered a "joint state interface" and a "joint effort interface" for all my joints and created the hardware-interface class. In my main program I created the controller_manager passing the created object as explained in the same tutorial. I could compile the code and run the so created control-loop; when it is running I can see the /controller_manager services trough "rosservice list".

My question is: if I want to use some "effort_controllers/JointPositionController" for my joints, how should I load them? As a beginning, I built a yaml configuration file and a launch file to load a joint controller as follows:

yaml file

robot: #what should robot be for? Package name? Namespace?
rHip_position_controller:
type: effort_controllers/JointPositionController
joint: rHip
pid: {p: 100.0, i: 0.01, d: 10.0} #random example values

and launcher

rosparam file="$(find biomot_control)/config/biomot_config.yaml" command="load"

node name="controller_spawner" pkg="controller_manager" type="spawner" respawn="false" output="screen" args="rHip_position_controller"

But when I launch it, it blocks at the step: Loading controller: rHip_position_controller. Am I missing any step or doing something wrong?

Also running "rosrun controller_manager controller_manager list-types" blocks without prompting any error or answer.

Thank you very much for the attention.

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Originally posted by MarcoB on ROS Answers with karma: 28 on 2015-03-11

Post score: 0

Answer 1

But when I launch it, it blocks at the step: [..]

[..]

Also running "rosrun controller_manager controller_manager list-types" blocks [..]

This reminds me of Unresponding control node on the ros-sig-robot-control list.

Without access to your actual code: make sure you service ros_control callbacks somewhere, as if those are not processed, it cannot correctly handle incoming service requests, which typically results in the hangs you are describing.

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Originally posted by gvdhoorn with karma: 86574 on 2015-03-11

This answer was ACCEPTED on the original site

Post score: 2

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Original comments

Comment by MarcoB on 2015-03-11:
Thank you, that seems to be my problem. I fixed with a ros::spinOnce() in my control loop, I'm not sure that's the correct way to do it. Now I'm facing another problem, when loading:"Could not find parameter robot_description on param serv." I made a urdf file but I can't figure out how to load it.

Comment by MarcoB on 2015-03-11:
EDIT: I had to start a dedicate thread running ros::spin as explained in the linked discussion. with position interfaces now controllers can load fine, to run effort interfaces I still need to understand how to get a proper xml description file from the urdf file.

Comment by gvdhoorn on 2015-03-12:
You might be interested in the ros_control_boilerplate package by Dave Coleman.

Comment by MarcoB on 2015-03-12:
Very interesting, thank you very much!