FAQ

This page provides answers to questions that are frequently asked by users of the planner. If you have a question that is not answered here, please contact us or add an issue to the issue tracker.

Question 1:

Error message: No p gain specified for pid. Namespace: /ur10/gazebo_ros_control/pid_gains/<joint_name>

This error mentions the missing P gains resulting from dependencies with the gazebo-ros-control package. Since we define a velocity controller to control the simulated robot, we don't need to set the P gain. If we select a P gain, the velocity controller will be controlled by an effort since we add another controller between the commanded velocities and the simulated robot, which leads to a robot motion even at a standstill. Please also refer to this ROS forum entry (https://answers.ros.org/question/293830/what-is-the-fix-for-no-p-gain-specified-for-pid-namespace-gazebo_ros_controlpid_gainsback_right_wheel_joint-ros-melodic/) which discusses this error more detailed, as well as this issue for the gazebo-ros-control package (https://github.com/ros-simulation/gazebo_ros_pkgs/issues/886).

If this issue is fixed at some point in the future, we will include this bug fix.

Question 2:

Warn message: TF_REPEATED_DATA ignoring data with redundant timestamp for frame <frame_name> (parent mocap) at time xx.xxxxxx according to authority unknown_publisher

This is an issue with the ROS melodic to noetic upgrade. If two transforms in ROS noetic have the same frame and timestamp a warning is thrown. This is not an issue for the planner and can be ignored. Nevertheless, this warning can be avoided by resorting to the messages in the rosbag test_motion based on the header timestamps and not the order in which they are received. The sorting uses the code from http://wiki.ros.org/rosbag/Cookbook and saves the rosbag in a new file "test_motion_noetic.bag" for the noetic branch.