Package Summary

Tags No category tags.
Version 2.2.1
License BSD-3-Clause
Build type AMENT_CMAKE
Use RECOMMENDED

Repository Summary

Checkout URI https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git
VCS Type git
VCS Version main
Last Updated 2022-06-28
Dev Status DEVELOPED
CI status No Continuous Integration
Released RELEASED
Tags No category tags.
Contributing Help Wanted (0)
Good First Issues (0)
Pull Requests to Review (0)

Package Description

Provides controllers that use the speed scaling interface of Universal Robots.

Additional Links

Maintainers

  • Denis Stogl
  • Felix Exner
  • Robert Wilbrandt

Authors

  • Marvin Große Besselmann
  • Lovro Ivanov

ur_controllers

This package contains controllers and hardware interface for ros_control that are special to the UR robot family. Currently this contains

  • A speed_scaling_interface to read the value of the current speed scaling into controllers.
  • A scaled_joint_command_interface that provides access to joint values and commands in combination with the speed scaling value.
  • A speed_scaling_state_controller that publishes the current execution speed as reported by the robot to a topic interface. Values are floating points between 0 and 1.
  • A scaled_joint_trajectory_controller that is similar to the joint_trajectory_controller, but it uses the speed scaling reported by the robot to reduce progress in the trajectory.

About this package

This package contains controllers not being available in the default ros_control set. They are created to support more features offered by the UR robot family. Any of these controllers are example implementations for certain features and are intended to be generalized and merged into the default ros_control controller set at some future point.

Controller description

This packages offers a couple of specific controllers that will be explained in the following sections.

ur_controllers/SpeedScalingStateBroadcaster

This controller publishes the current actual execution speed as reported by the robot. Values are floating points between 0 and 1.

In the ur_robot_driver this is calculated by multiplying the two RTDE data fields speed_scaling (which should be equal to the value shown by the speed slider position on the teach pendant) and target_speed_fraction (Which is the fraction to which execution gets slowed down by the controller).

position_controllers/ScaledJointTrajectoryController and velocity_controllers/ScaledJointTrajectoryController

These controllers work similar to the well-known joint_trajectory_controller.

However, they are extended to handle the robot's execution speed specifically. Because the default joint_trajectory_controller would interpolate the trajectory with the configured time constraints (ie: always assume maximum velocity and acceleration supported by the robot), this could lead to significant path deviation due to multiple reasons: - The speed slider on the robot might not be at 100%, so motion commands sent from ROS would effectively get scaled down resulting in a slower execution. - The robot could scale down motions based on configured safety limits resulting in a slower motion than expected and therefore not reaching the desired target in a control cycle. - Motions might not be executed at all, e.g. because the robot is E-stopped or in a protective stop - Motion commands sent to the robot might not be interpreted, e.g. because there is no external_control program node running on the robot controller. - The program interpreting motion commands could be paused.

The following plot illustrates the problem: Trajectory execution with default trajectory controller

The graph shows a trajectory with one joint being moved to a target point and back to its starting point. As the joint's speed is limited to a very low setting on the teach pendant, speed scaling (black line) activates and limits the joint speed (green line). As a result, the target trajectory (light blue) doesn't get executed by the robot, but instead the pink trajectory is executed. The vertical distance between the light blue line and the pink line is the path error in each control cycle. We can see that the path deviation gets above 300 degrees at some point and the target point at -6 radians never gets reached.

All of the cases mentioned above are addressed by the scaled trajectory versions. Trajectory execution can be transparently scaled down using the speed slider on the teach pendant without leading to additional path deviations. Pausing the program or hitting the E-stop effectively leads to speed_scaling being 0 meaning the trajectory will not be continued until the program is continued. This way, trajectory executions can be explicitly paused and continued.

With the scaled version of the trajectory controller the example motion shown in the previous diagram becomes: Trajectory execution with scaled_joint_trajectory_controller

The deviation between trajectory interpolation on the ROS side and actual robot execution stays minimal and the robot reaches the intermediate setpoint instead of returning "too early" as in the example above.

Under the hood this is implemented by proceeding the trajectory not by a full time step but only by the fraction determined by the current speed scaling. If speed scaling is currently at 50% then interpolation of the current control cycle will start half a time step after the beginning of the previous control cycle.

CHANGELOG

Changelog for package ur_controllers

2.2.1 (2022-06-27)

2.2.0 (2022-06-20)

  • Updated package maintainers
  • Prepare for humble (#394)
  • Update dependencies on all packages (#391)
  • Update controllers\' API (#351)
  • Update binary dependencies (#344)
  • Use upstream fts_broadcaster (#304)
  • Update license to BSD-3-Clause (#277)
  • Added controller stopper node (#309)
  • Add missing dependency on angles and update formatting for linters. (#283)
  • Payload service (#238)
  • Integration tests improvement (#206)
  • Add resend program service and enable headless mode (#198)
  • Update controllers adding dt in to update as in ros2_control (#171)
  • Update main branch with ros-controls changes (#160)
  • Update CI configuration to support galactic and rolling (#142)
  • Modify parameter declaration - approach equalization with ros-controls dependencies (#152)
  • Moved registering publisher and service to on_active (#151)
  • Correct formatting, include std::vector and update ros2_controller to master branch in repo file.
  • Correct check for fixed has_trajectory_msg() See: https://github.com/ros-controls/ros2_controllers/commit/32f089b3f3b53a817412c6bbce9046028786431e
  • Update for changes to ros2_control and ros2_controllers See: https://github.com/ros-controls/ros2_control/commit/156a3f6aaed319585a8a1fd445693e2e08c30ccd and: https://github.com/ros-controls/ros2_controllers/commit/612f610c24d026a41abd2dd026902c672cf778c9#diff-5d3e18800b3a217b37b91036031bdb170f5183970f54d1f951bb12f2e4847706
  • Fix gpio controller (#103)
  • Fixed speed slider service call (#100)
  • Reintegrating missing ur_client_library dependency since the break the building process (#97)
  • Setting speed slider with range of 0.0-1.0 and added warnings if range is exceeded (#88)
  • Fix move to home bug (#92)
  • Review CI by correcting the configurations (#71)
  • Add support for gpios, update MoveIt and ros2_control launching (#66)
  • Fix warning about deprecated controller_interface::return_type::SUCCESS (#68)
  • Use GitHub Actions, use pre-commit formatting (#56)
  • Scaled Joint Trajectory Controller (#43)
  • Only load speed scaling interface
  • Removed controller from config file to realign with current branch status
  • Removed last remnants of joint_state_controller
  • Added publisher rate
  • Code formatting and cleanup
  • Added publisher for speed scaling factor
  • Initial version of the speed_scaling_state_controller
  • Update licence.
  • Fix clang tidy in multiple pkgs.
  • Update force torque state controller.
  • Prepare for testing.
  • Update ft state controller with ros2_control changes.
  • Remove lifecycle node (update with ros2_control changes).
  • Claim individual resources.
  • Add force torque controller.
  • Claim individual resources.
  • Add force torque controller.
  • Add XML schema to all package.xml files Better enable ament_xmllint to check validity.
  • Update package.xml files so ros2 pkg list shows all pkgs
  • Clean out ur_controllers, it needs a complete rewrite
  • Update CMakeLists and package.xml for:
    • ur5_moveit_config
    • ur_bringup
    • ur_description
  • Change pkg versions to 0.0.0
  • Contributors: AndyZe, Denis Stogl, Denis

Wiki Tutorials

See ROS Wiki Tutorials for more details.

Source Tutorials

Not currently indexed.

Launch files

No launch files found

Messages

No message files found.

Services

No service files found

Plugins

No plugins found.

Recent questions tagged ur_controllers at answers.ros.org

Package Summary

Tags No category tags.
Version 2.1.1
License BSD-3-Clause
Build type AMENT_CMAKE
Use RECOMMENDED

Repository Summary

Checkout URI https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git
VCS Type git
VCS Version galactic
Last Updated 2022-06-28
Dev Status DEVELOPED
CI status No Continuous Integration
Released RELEASED
Tags No category tags.
Contributing Help Wanted (0)
Good First Issues (0)
Pull Requests to Review (0)

Package Description

Provides controllers that use the speed scaling interface of Universal Robots.

Additional Links

Maintainers

  • Denis Stogl
  • Felix Exner
  • Tristan Schnell

Authors

  • Marvin Große Besselmann
  • Lovro Ivanov

ur_controllers

This package contains controllers and hardware interface for ros_control that are special to the UR robot family. Currently this contains

  • A speed_scaling_interface to read the value of the current speed scaling into controllers.
  • A scaled_joint_command_interface that provides access to joint values and commands in combination with the speed scaling value.
  • A speed_scaling_state_controller that publishes the current execution speed as reported by the robot to a topic interface. Values are floating points between 0 and 1.
  • A scaled_joint_trajectory_controller that is similar to the joint_trajectory_controller, but it uses the speed scaling reported by the robot to reduce progress in the trajectory.

About this package

This package contains controllers not being available in the default ros_control set. They are created to support more features offered by the UR robot family. Any of these controllers are example implementations for certain features and are intended to be generalized and merged into the default ros_control controller set at some future point.

Controller description

This packages offers a couple of specific controllers that will be explained in the following sections.

ur_controllers/SpeedScalingStateBroadcaster

This controller publishes the current actual execution speed as reported by the robot. Values are floating points between 0 and 1.

In the ur_robot_driver this is calculated by multiplying the two RTDE data fields speed_scaling (which should be equal to the value shown by the speed slider position on the teach pendant) and target_speed_fraction (Which is the fraction to which execution gets slowed down by the controller).

position_controllers/ScaledJointTrajectoryController and velocity_controllers/ScaledJointTrajectoryController

These controllers work similar to the well-known joint_trajectory_controller.

However, they are extended to handle the robot's execution speed specifically. Because the default joint_trajectory_controller would interpolate the trajectory with the configured time constraints (ie: always assume maximum velocity and acceleration supported by the robot), this could lead to significant path deviation due to multiple reasons: - The speed slider on the robot might not be at 100%, so motion commands sent from ROS would effectively get scaled down resulting in a slower execution. - The robot could scale down motions based on configured safety limits resulting in a slower motion than expected and therefore not reaching the desired target in a control cycle. - Motions might not be executed at all, e.g. because the robot is E-stopped or in a protective stop - Motion commands sent to the robot might not be interpreted, e.g. because there is no external_control program node running on the robot controller. - The program interpreting motion commands could be paused.

The following plot illustrates the problem: Trajectory execution with default trajectory controller

The graph shows a trajectory with one joint being moved to a target point and back to its starting point. As the joint's speed is limited to a very low setting on the teach pendant, speed scaling (black line) activates and limits the joint speed (green line). As a result, the target trajectory (light blue) doesn't get executed by the robot, but instead the pink trajectory is executed. The vertical distance between the light blue line and the pink line is the path error in each control cycle. We can see that the path deviation gets above 300 degrees at some point and the target point at -6 radians never gets reached.

All of the cases mentioned above are addressed by the scaled trajectory versions. Trajectory execution can be transparently scaled down using the speed slider on the teach pendant without leading to additional path deviations. Pausing the program or hitting the E-stop effectively leads to speed_scaling being 0 meaning the trajectory will not be continued until the program is continued. This way, trajectory executions can be explicitly paused and continued.

With the scaled version of the trajectory controller the example motion shown in the previous diagram becomes: Trajectory execution with scaled_joint_trajectory_controller

The deviation between trajectory interpolation on the ROS side and actual robot execution stays minimal and the robot reaches the intermediate setpoint instead of returning "too early" as in the example above.

Under the hood this is implemented by proceeding the trajectory not by a full time step but only by the fraction determined by the current speed scaling. If speed scaling is currently at 50% then interpolation of the current control cycle will start half a time step after the beginning of the previous control cycle.

CHANGELOG

Changelog for package ur_controllers

2.1.1 (2022-05-05)

2.1.0 (2022-05-03)

  • Updated package maintainers (#360)
  • Use upstream fts_broadcaster (#304)
  • Update license to BSD-3-Clause (#277)
  • Added controller stopper node (#309)
  • Add missing dependency on angles and update formatting for linters. (#283)
  • Payload service (#238)
  • Integration tests improvement (#206)
  • Add resend program service and enable headless mode (#198)
  • Update controllers adding dt in to update as in ros2_control (#171)
  • Update main branch with ros-controls changes (#160)
  • Update CI configuration to support galactic and rolling (#142)
  • Modify parameter declaration - approach equalization with ros-controls dependencies (#152)
  • Moved registering publisher and service to on_active (#151)
  • Correct formatting, include std::vector and update ros2_controller to master branch in repo file.
  • Correct check for fixed has_trajectory_msg() See: https://github.com/ros-controls/ros2_controllers/commit/32f089b3f3b53a817412c6bbce9046028786431e
  • Update for changes to ros2_control and ros2_controllers See: https://github.com/ros-controls/ros2_control/commit/156a3f6aaed319585a8a1fd445693e2e08c30ccd and: https://github.com/ros-controls/ros2_controllers/commit/612f610c24d026a41abd2dd026902c672cf778c9#diff-5d3e18800b3a217b37b91036031bdb170f5183970f54d1f951bb12f2e4847706
  • Fix gpio controller (#103)
  • Fixed speed slider service call (#100)
  • Reintegrating missing ur_client_library dependency since the break the building process (#97)
  • Setting speed slider with range of 0.0-1.0 and added warnings if range is exceeded (#88)
  • Fix move to home bug (#92)
  • Review CI by correcting the configurations (#71)
  • Add support for gpios, update MoveIt and ros2_control launching (#66)
  • Fix warning about deprecated controller_interface::return_type::SUCCESS (#68)
  • Use GitHub Actions, use pre-commit formatting (#56)
  • Scaled Joint Trajectory Controller (#43)
  • Only load speed scaling interface
  • Removed controller from config file to realign with current branch status
  • Removed last remnants of joint_state_controller
  • Added publisher rate
  • Code formatting and cleanup
  • Added publisher for speed scaling factor
  • Initial version of the speed_scaling_state_controller
  • Update licence.
  • Fix clang tidy in multiple pkgs.
  • Update force torque state controller.
  • Prepare for testing.
  • Update ft state controller with ros2_control changes.
  • Remove lifecycle node (update with ros2_control changes).
  • Claim individual resources.
  • Add force torque controller.
  • Claim individual resources.
  • Add force torque controller.
  • Add XML schema to all package.xml files Better enable ament_xmllint to check validity.
  • Update package.xml files so ros2 pkg list shows all pkgs
  • Clean out ur_controllers, it needs a complete rewrite
  • Update CMakeLists and package.xml for:
    • ur5_moveit_config
    • ur_bringup
    • ur_description
  • Change pkg versions to 0.0.0
  • Contributors: AndyZe, Denis Stogl, Denis

Wiki Tutorials

See ROS Wiki Tutorials for more details.

Source Tutorials

Not currently indexed.

Launch files

No launch files found

Messages

No message files found.

Services

No service files found

Plugins

No plugins found.

Recent questions tagged ur_controllers at answers.ros.org

Package Summary

Tags No category tags.
Version 2.0.0
License Apache License 2.0
Build type AMENT_CMAKE
Use RECOMMENDED

Repository Summary

Checkout URI https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git
VCS Type git
VCS Version foxy
Last Updated 2022-06-28
Dev Status DEVELOPED
CI status No Continuous Integration
Released RELEASED
Tags No category tags.
Contributing Help Wanted (0)
Good First Issues (0)
Pull Requests to Review (0)

Package Description

Provides controllers that use the speed scaling interface of Universal Robots.

Additional Links

Maintainers

  • Marvin Große Besselmann
  • Lovro Ivanov
  • Denis Stogl
  • Andy Zelenak

Authors

  • Marvin Große Besselmann
  • Lovro Ivanov

ur_controllers

This package contains controllers and hardware interface for ros_control that are special to the UR robot family. Currently this contains

  • A speed_scaling_interface to read the value of the current speed scaling into controllers.
  • A scaled_joint_command_interface that provides access to joint values and commands in combination with the speed scaling value.
  • A speed_scaling_state_controller that publishes the current execution speed as reported by the robot to a topic interface. Values are floating points between 0 and 1.
  • A scaled_joint_trajectory_controller that is similar to the joint_trajectory_controller, but it uses the speed scaling reported by the robot to reduce progress in the trajectory.

About this package

This package contains controllers not being available in the default ros_control set. They are created to support more features offered by the UR robot family. Any of these controllers are example implementations for certain features and are intended to be generalized and merged into the default ros_control controller set at some future point.

Controller description

This packages offers a couple of specific controllers that will be explained in the following sections.

ur_controllers/SpeedScalingStateBroadcaster

This controller publishes the current actual execution speed as reported by the robot. Values are floating points between 0 and 1.

In the ur_robot_driver this is calculated by multiplying the two RTDE data fields speed_scaling (which should be equal to the value shown by the speed slider position on the teach pendant) and target_speed_fraction (Which is the fraction to which execution gets slowed down by the controller).

position_controllers/ScaledJointTrajectoryController and velocity_controllers/ScaledJointTrajectoryController

These controllers work similar to the well-known joint_trajectory_controller.

However, they are extended to handle the robot's execution speed specifically. Because the default joint_trajectory_controller would interpolate the trajectory with the configured time constraints (ie: always assume maximum velocity and acceleration supported by the robot), this could lead to significant path deviation due to multiple reasons: - The speed slider on the robot might not be at 100%, so motion commands sent from ROS would effectively get scaled down resulting in a slower execution. - The robot could scale down motions based on configured safety limits resulting in a slower motion than expected and therefore not reaching the desired target in a control cycle. - Motions might not be executed at all, e.g. because the robot is E-stopped or in a protective stop - Motion commands sent to the robot might not be interpreted, e.g. because there is no external_control program node running on the robot controller. - The program interpreting motion commands could be paused.

The following plot illustrates the problem: Trajectory execution with default trajectory controller

The graph shows a trajectory with one joint being moved to a target point and back to its starting point. As the joint's speed is limited to a very low setting on the teach pendant, speed scaling (black line) activates and limits the joint speed (green line). As a result, the target trajectory (light blue) doesn't get executed by the robot, but instead the pink trajectory is executed. The vertical distance between the light blue line and the pink line is the path error in each control cycle. We can see that the path deviation gets above 300 degrees at some point and the target point at -6 radians never gets reached.

All of the cases mentioned above are addressed by the scaled trajectory versions. Trajectory execution can be transparently scaled down using the speed slider on the teach pendant without leading to additional path deviations. Pausing the program or hitting the E-stop effectively leads to speed_scaling being 0 meaning the trajectory will not be continued until the program is continued. This way, trajectory executions can be explicitly paused and continued.

With the scaled version of the trajectory controller the example motion shown in the previous diagram becomes: Trajectory execution with scaled_joint_trajectory_controller

The deviation between trajectory interpolation on the ROS side and actual robot execution stays minimal and the robot reaches the intermediate setpoint instead of returning "too early" as in the example above.

Under the hood this is implemented by proceeding the trajectory not by a full time step but only by the fraction determined by the current speed scaling. If speed scaling is currently at 50% then interpolation of the current control cycle will start half a time step after the beginning of the previous control cycle.

CHANGELOG

Changelog for package ur_controllers

2.0.0 (2022-06-20)

  • Updated package dependencies (#399)
  • Foxy controller stopper (#324)
  • Fixing foxy CI (#157)
  • Moved registering publisher and service to on_active (#151)
  • Correct formatting, include std::vector and update ros2_controller to master branch in repo file.
  • Correct check for fixed has_trajectory_msg()
  • Update for changes to ros2_control and ros2_controllers
  • Fix gpio controller (#103)
  • Fixed speed slider service call (#100)
  • Reintegrating missing ur_client_library dependency since the break the building process (#97)
  • Setting speed slider with range of 0.0-1.0 and added warnings if range is exceeded (#88)
  • Fix move to home bug (#92)
  • Last fix-ups
  • Some intermediate commit
  • Last fix-ups
  • Review CI by correcting the configurations (#71)
  • Add support for gpios, update MoveIt and ros2_control launching (#66)
  • Fix warning about deprecated controller_interface::return_type::SUCCESS (#68)
  • Use GitHub Actions, use pre-commit formatting (#56)
  • Scaled Joint Trajectory Controller (#43)
  • Code cleanup
  • Only load speed scaling interface
  • Removed controller from config file to realign with current branch
  • Removed last remnants of joint_state_controller
  • Added publisher rate
  • Code formatting and cleanup
  • Added publisher for speed scaling factor
  • Initial version of the speed_scaling_state_controller Controller is base on the current joint_state_controller of ros2 control
  • Update licence.
  • Fix clang tidy in multiple pkgs.
  • Update force torque state controller.
  • Prepare for testing.
  • Update ft state controller with ros2_control changes.
  • Remove lifecycle node (update with ros2_control changes).
  • Claim individual resources.
  • Add force torque controller.
  • Claim individual resources.
  • Add force torque controller.
  • Add XML schema to all package.xml files Better enable ament_xmllint to check validity.
  • Silence ament_lint_cmake errors
  • Update package.xml files so ros2 pkg list shows all pkgs
  • Clean out ur_controllers, it needs a complete rewrite
  • Update CMakeLists and package.xml for:
    • ur5_moveit_config
    • ur_bringup
    • ur_description
  • Change pkg versions to 0.0.0
  • Contributors: AndyZe, Denis Stogl, Denis

Wiki Tutorials

See ROS Wiki Tutorials for more details.

Source Tutorials

Not currently indexed.

Launch files

No launch files found

Messages

No message files found.

Services

No service files found

Plugins

No plugins found.

Recent questions tagged ur_controllers at answers.ros.org

Package Summary

Tags No category tags.
Version 2.2.1
License BSD-3-Clause
Build type AMENT_CMAKE
Use RECOMMENDED

Repository Summary

Checkout URI https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git
VCS Type git
VCS Version main
Last Updated 2022-06-28
Dev Status DEVELOPED
CI status No Continuous Integration
Released RELEASED
Tags No category tags.
Contributing Help Wanted (0)
Good First Issues (0)
Pull Requests to Review (0)

Package Description

Provides controllers that use the speed scaling interface of Universal Robots.

Additional Links

Maintainers

  • Denis Stogl
  • Felix Exner
  • Robert Wilbrandt

Authors

  • Marvin Große Besselmann
  • Lovro Ivanov

ur_controllers

This package contains controllers and hardware interface for ros_control that are special to the UR robot family. Currently this contains

  • A speed_scaling_interface to read the value of the current speed scaling into controllers.
  • A scaled_joint_command_interface that provides access to joint values and commands in combination with the speed scaling value.
  • A speed_scaling_state_controller that publishes the current execution speed as reported by the robot to a topic interface. Values are floating points between 0 and 1.
  • A scaled_joint_trajectory_controller that is similar to the joint_trajectory_controller, but it uses the speed scaling reported by the robot to reduce progress in the trajectory.

About this package

This package contains controllers not being available in the default ros_control set. They are created to support more features offered by the UR robot family. Any of these controllers are example implementations for certain features and are intended to be generalized and merged into the default ros_control controller set at some future point.

Controller description

This packages offers a couple of specific controllers that will be explained in the following sections.

ur_controllers/SpeedScalingStateBroadcaster

This controller publishes the current actual execution speed as reported by the robot. Values are floating points between 0 and 1.

In the ur_robot_driver this is calculated by multiplying the two RTDE data fields speed_scaling (which should be equal to the value shown by the speed slider position on the teach pendant) and target_speed_fraction (Which is the fraction to which execution gets slowed down by the controller).

position_controllers/ScaledJointTrajectoryController and velocity_controllers/ScaledJointTrajectoryController

These controllers work similar to the well-known joint_trajectory_controller.

However, they are extended to handle the robot's execution speed specifically. Because the default joint_trajectory_controller would interpolate the trajectory with the configured time constraints (ie: always assume maximum velocity and acceleration supported by the robot), this could lead to significant path deviation due to multiple reasons: - The speed slider on the robot might not be at 100%, so motion commands sent from ROS would effectively get scaled down resulting in a slower execution. - The robot could scale down motions based on configured safety limits resulting in a slower motion than expected and therefore not reaching the desired target in a control cycle. - Motions might not be executed at all, e.g. because the robot is E-stopped or in a protective stop - Motion commands sent to the robot might not be interpreted, e.g. because there is no external_control program node running on the robot controller. - The program interpreting motion commands could be paused.

The following plot illustrates the problem: Trajectory execution with default trajectory controller

The graph shows a trajectory with one joint being moved to a target point and back to its starting point. As the joint's speed is limited to a very low setting on the teach pendant, speed scaling (black line) activates and limits the joint speed (green line). As a result, the target trajectory (light blue) doesn't get executed by the robot, but instead the pink trajectory is executed. The vertical distance between the light blue line and the pink line is the path error in each control cycle. We can see that the path deviation gets above 300 degrees at some point and the target point at -6 radians never gets reached.

All of the cases mentioned above are addressed by the scaled trajectory versions. Trajectory execution can be transparently scaled down using the speed slider on the teach pendant without leading to additional path deviations. Pausing the program or hitting the E-stop effectively leads to speed_scaling being 0 meaning the trajectory will not be continued until the program is continued. This way, trajectory executions can be explicitly paused and continued.

With the scaled version of the trajectory controller the example motion shown in the previous diagram becomes: Trajectory execution with scaled_joint_trajectory_controller

The deviation between trajectory interpolation on the ROS side and actual robot execution stays minimal and the robot reaches the intermediate setpoint instead of returning "too early" as in the example above.

Under the hood this is implemented by proceeding the trajectory not by a full time step but only by the fraction determined by the current speed scaling. If speed scaling is currently at 50% then interpolation of the current control cycle will start half a time step after the beginning of the previous control cycle.

CHANGELOG

Changelog for package ur_controllers

2.2.1 (2022-06-27)

2.2.0 (2022-06-20)

  • Updated package maintainers
  • Prepare for humble (#394)
  • Update dependencies on all packages (#391)
  • Update controllers\' API (#351)
  • Update binary dependencies (#344)
  • Use upstream fts_broadcaster (#304)
  • Update license to BSD-3-Clause (#277)
  • Added controller stopper node (#309)
  • Add missing dependency on angles and update formatting for linters. (#283)
  • Payload service (#238)
  • Integration tests improvement (#206)
  • Add resend program service and enable headless mode (#198)
  • Update controllers adding dt in to update as in ros2_control (#171)
  • Update main branch with ros-controls changes (#160)
  • Update CI configuration to support galactic and rolling (#142)
  • Modify parameter declaration - approach equalization with ros-controls dependencies (#152)
  • Moved registering publisher and service to on_active (#151)
  • Correct formatting, include std::vector and update ros2_controller to master branch in repo file.
  • Correct check for fixed has_trajectory_msg() See: https://github.com/ros-controls/ros2_controllers/commit/32f089b3f3b53a817412c6bbce9046028786431e
  • Update for changes to ros2_control and ros2_controllers See: https://github.com/ros-controls/ros2_control/commit/156a3f6aaed319585a8a1fd445693e2e08c30ccd and: https://github.com/ros-controls/ros2_controllers/commit/612f610c24d026a41abd2dd026902c672cf778c9#diff-5d3e18800b3a217b37b91036031bdb170f5183970f54d1f951bb12f2e4847706
  • Fix gpio controller (#103)
  • Fixed speed slider service call (#100)
  • Reintegrating missing ur_client_library dependency since the break the building process (#97)
  • Setting speed slider with range of 0.0-1.0 and added warnings if range is exceeded (#88)
  • Fix move to home bug (#92)
  • Review CI by correcting the configurations (#71)
  • Add support for gpios, update MoveIt and ros2_control launching (#66)
  • Fix warning about deprecated controller_interface::return_type::SUCCESS (#68)
  • Use GitHub Actions, use pre-commit formatting (#56)
  • Scaled Joint Trajectory Controller (#43)
  • Only load speed scaling interface
  • Removed controller from config file to realign with current branch status
  • Removed last remnants of joint_state_controller
  • Added publisher rate
  • Code formatting and cleanup
  • Added publisher for speed scaling factor
  • Initial version of the speed_scaling_state_controller
  • Update licence.
  • Fix clang tidy in multiple pkgs.
  • Update force torque state controller.
  • Prepare for testing.
  • Update ft state controller with ros2_control changes.
  • Remove lifecycle node (update with ros2_control changes).
  • Claim individual resources.
  • Add force torque controller.
  • Claim individual resources.
  • Add force torque controller.
  • Add XML schema to all package.xml files Better enable ament_xmllint to check validity.
  • Update package.xml files so ros2 pkg list shows all pkgs
  • Clean out ur_controllers, it needs a complete rewrite
  • Update CMakeLists and package.xml for:
    • ur5_moveit_config
    • ur_bringup
    • ur_description
  • Change pkg versions to 0.0.0
  • Contributors: AndyZe, Denis Stogl, Denis

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