Hello,
I am trying to implement a custom hardware interface for a 3-joint manipulator with ros_control. I was following the tutorial on the matter pretty closely. The problem is that while the controller_manager apparently gets started, service calls like list_controllers just hang. I am also unable to load any controllers, as this call also hangs.
To narrow down the possible causes, I created a test node (called test_iface) which contains almost exactly the code from the tutorial mentioned above, i.e., two joints, "A" and "B", and the interface implements a JointStateInterface as well as a PositionJointInterface. The read() and write() methods simply write a message to stdout (ROS_INFO).
Now, when I start this test node, the read/write loop gets executed properly, as I get the ROS_INFO messages from them. Also, the output of rosservice list is:
user@ubuntu:~$ rosservice list
/controller_manager/list_controller_types
/controller_manager/list_controllers
/controller_manager/load_controller
/controller_manager/reload_controller_libraries
/controller_manager/switch_controller
/controller_manager/unload_controller
/joint_state_publisher/get_loggers
/joint_state_publisher/set_logger_level
/rosout/get_loggers
/rosout/set_logger_level
/test_iface_node/get_loggers
/test_iface_node/set_logger_level
So the controller_manager seems to start up okay. However, when I try to call the list_controllers service (via rqt; expecting an empty list, since no controllers have been loaded yet), the request just hangs and nothing happens.
When I use gazebo instead of my custom HW interface, the service call to list_controllers returns an empty list, as expected. (on a side note, if I run "rosrun controller_manager controller_manager list", that always seems to hang).
What can I do to debug this? Do you have any suggestions as to what I might be doing wrong? The test_iface code is the MyRobot class from the tutorial, extended by a read() and write() that only print debug messages, and this main method:
int main(int argc, char** argv)
{
ros::init(argc, argv, "test_iface_node");
ros::NodeHandle nh;
MyRobot robot;
controller_manager::ControllerManager cm(&robot);
ros::Time ts = ros::Time::now();
while (true)
{
ros::Duration d = ts - ros::Time::now();
ts = ros::Time::now();
robot.read();
cm.update(ts, d);
robot.write();
sleep(1);
}
return 0;
}
Any hints or suggestions are welcome. Thanks!
Originally posted by onkel_keks on ROS Answers with karma: 28 on 2015-02-03
Post score: 1
Original comments
Comment by cyborg-x1 on 2015-12-01:
I was using your code as example (was in a real need for a simple one) ... well there is a little issue:
ros::Duration d = ts - ros::Time::now(); //is negative because time now is later and bigger ...
Must be like ros::Duration d = ros::Time::now() - ts;
Comment by cyborg-x1 on 2015-12-01:
My example if you anybody is interested: https://github.com/cyborg-x1/ros_control_test (based on yours, now with fixed time calculation ;-) )
Comment by bario on 2017-02-07:
cyborg-x1,
Your link was quite helpful for me. Thanks
Comment by SofiaGr on 2017-05-26:
hello, what needs to be added in cyborg-x1's example so that the robot can move? Can I add rostopic commands into the program? I am trying to write a program that will ask for user input, as to how to move a link and will give back the actual position of the link.
Comment by cyborg-x1 on 2017-05-31:
As far as I remember my example you should have the topic cmd_vel as in the launchfile there is a diff drive controller loaded. Set linear.x part of the message for forward backward speed and angular.z for left/right.
