I found myself with some difficulties to understand how to use the control_toolbox::pid class. After struggling to make it work, here I share my findings with a tutorial package to get you set up!

First, docs from the Pid class: http://docs.ros.org/api/control_toolbox/html/classcontrol__toolbox_1_1Pid.html

Mainly the interesting bits of this package are in src/example.cpp.

It implements a pid controller for a made up geometry_msgs/Twist cmd_vel. There is nothing to actually control for real, but you can play with the parts and find a working pid implementation with dynamic reconfigure to tune it available.

You should be able to build this package with something like:

mkdir -p pid_ws/src
cd pid_ws/src
git clone https://github.com/awesomebytes/control_toolbox_pid_tutorial
cd ..
catkin build
source devel/setup.bash

You can run the example node with:

rosrun control_toolbox_pid_tutorial pid_example

Or check it out with a launchfile setting up the PID parameters:

roslaunch control_toolbox_pid_tutorial example.launch

Looks like this:

If before starting the node that contains the PID you set the parameter publish_state in the param server to true, you'll get access to the PID internal state.

$ rostopic echo /my_namespace/my_pid/state
header: 
  seq: 992
  stamp: 
    secs: 1545405985
    nsecs: 449541433
  frame_id: ''
timestep: 
  secs: 0
  nsecs: 100291320
error: 0.0
error_dot: 0.0
p_error: 0.0
i_error: 0.0
d_error: 0.0
p_term: 0.0
i_term: 0.0
d_term: 0.0
i_max: 10.0
i_min: -10.0
output: 0.0
---

In my case, to debug what is going on I use:

• rosrun rqt_robot_steering rqt_robot_steering (or rqt adding the plugin) to send geometry_msgs/Twist commands to a topic.
• rosrun rqt_reconfigure rqt_reconfigure (or rqt adding the plugin) to play with the PID gains.
• rosrun plotjuggler PlotJuggler PlotJuggler to visualize in real time the different inputs and outputs, including the PID state, in case that helps debugging (it may help to choose i_clamp values of the PID). rqt_multiplot could be used too (as rqt plugin probably).
• Some rostopic echo of the topics that come in and out. They are useful sometimes too.
• rosbag record and rosbag play to check in an offline fashion.

sudo apt-get install ros-kinetic-control-toolbox ros-kinetic-rqt-reconfigure ros-kinetic-plotjuggler ros-kinetic-rqt-robot-steering

But chances are you already have them.