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linear_feedback_controller package from linear_feedback_controller repo

linear_feedback_controller

ROS Distro
rolling

Package Summary

Version	3.0.1
License	BSD-2-Clause
Build type	AMENT_CMAKE
Use	RECOMMENDED

Repository Summary

Description	ROS2 control linear feedback controller. It connects Ricatti gains based controllers with the hardware through ROS2 topics.
Checkout URI	https://github.com/loco-3d/linear-feedback-controller.git
VCS Type	git
VCS Version	main
Last Updated	2026-02-24
Dev Status	MAINTAINED
Released	UNRELEASED
Contributing	Help Wanted (-) Good First Issues (-) Pull Requests to Review (-)

Package Description

roscontrol controller package conputing a linear feedback. The user needs to provide a model of the robot and a list of controlled joint and the controller computes a linear feedback on the user defined state.

Additional Links

Website

Maintainers

Guilhem Saurel

Authors

Maximilien Naveau

README.md

linear feedback controller

This repository is aimed to be used with its public API the linear_feedback_controller_msgs.

These two packages are under the license BSD-2 license.

The current versions of these two packages can be found in their respective package.xml file. There must be an associated git tag in a shape of vX.Y.Z.

Follows a quick description of these package.

The linear_feedback_controller

In this package we implement a ros2_control controller. It is implementing a chainable controller pluggable with any kind of state estimator.

We implement a ROS 2 topic publisher sending:

base configuration (only if the robot has a free-flyer, identity otherwise)
base velocity (only if the robot has a free-flyer, identity otherwise)
joint positions
joint velocities
joint efforts (torques applied to the joints)

We send receive the response via a topic in the shape:

A feedback gain matrix
A feedforward term in torque
The state which was sent before used to linearize the control.

This allows us, for example, to use it on the Talos (1 and 3) robots with a remote controller using a whole body model predictive control based on croccodyl

For the interfacing of a fixed robot we add a joint_state_estimator which aims at providing a layer of filtering from the joint sensors.

In addition we provide a passthrough controller which aims at renaming some output interfaces downstream in case this is needed. Typically you may want the same configuration file for simulation and for the robot but the interfaces ffrom one to the other may not match. You can use the passthrough controller for this.

The linear_feedback_controller_msgs

This package contains the external user interface to the linear_feedback_controller package. It describes the sensor data exchanged in the previously cited ROS2 topics.

And in particular it offers a very simple ROS/Eigen conversion tooling. And a ROS/numpy conversion tooling. These are made to facilitate further computations with the Sensor data, and ease to fill in the Control message.

Please check the README.md of the package for more details.

Example of usage

This a ROS2 controller so on can simply look at the ROS2 control documentation. An example of configuration can be found in this repository here.

The example is extracted from the agimus-demos pacakges: https://github.com/agimus-project/agimus-demos

And in particular the setup of the LFC is in the agimus_demos_common package.

Build the package.

This package is base on ament_cmake hence one can simply use the standard:

git clone https://github.com/loco-3d/linear-feedback-controller.git
cd linear-feedback-controller
make _build
cd _build
cmake .. -DCMAKE_INSTALL_PREFIX=/path/to/your/install/folder
make
make install

Or one can use the ROS2 super build system colcon:

mkdir -p workspace/src
git -C workspace/src clone https://github.com/loco-3d/linear-feedback-controller.git
colcon build

One can also use nix to:

Check the package (builds and run tests):

git clone https://github.com/loco-3d/linear-feedback-controller.git
cd linear-feedback-controller
nix flake check -L

Build the package:

File truncated at 100 lines see the full file

CHANGELOG

Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Releases are available on the github repository.

Unreleased

3.0.1 - 2025-11-04

add jrl_cmakemodules to package.xml

3.0.0 - 2025-10-23

added

A passthrough_controller to simulate controllers on partial interface sets. Example in a certain robot there is one controller per joint on the robot but not in simulation. This passthrough controller helps the user to create a seemless interface for both the real robot and the simulation.

changed

Breaking API! The in and out interfaces can now be twicked interface by interface.

2.0.0 - 2025-04-14

Changed

Breaking change: migration ROS2
Splitting the ROS vs none ROS part of the code.

Added

Added unit-test for the math.

1.0.2 - 2023-04-03

Added

pal_statistics introspection.
computation of the ZMP in the controller for debugging
computation of the position of the pendulum base fro debugging.
computation of the CoM acceleration from the measured forces.

1.0.1 - 2023-03-21

Fixed

Fix the averaging filter implementation.

Changed

Update the usage of the Eigen API to save some code lines.

1.0.0 - 2023-03-17

Changed

Remove the msgs package and mv the lfc at the root of the git repository. msgs are now here: https://github.com/loco-3d/linear-feedback-controller-msgs

0.1.0 - 2023-03-17

Implementation of linear-feedback-controller in ROS1 for Talos PAL-Robotics robot.

Git changelogs

Package Dependencies

Deps	Name
	jrl_cmakemodules
	parameter_traits
	ament_cmake_auto
	ament_cmake_python
	ament_lint_auto
	gtest_vendor
	gmock_vendor
	rcl
	rclcpp
	rclcpp_lifecycle
	controller_interface
	control_toolbox
	hardware_interface
	message_filters
	nav_msgs
	sensor_msgs
	pluginlib
	realtime_tools
	pinocchio
	linear_feedback_controller_msgs
	pal_statistics
	generate_parameter_library
	rosidl_dynamic_typesupport

System Dependencies

Name
eigen
fmt

Dependant Packages

No known dependants.

Launch files

launch/talos_linear_feedback_controller.launch
- - spawn [default: true]
  - simulation [default: false]
  - ns [default: linear_feedback_controller]
  - debug_log [default: false]
  - default_params [default: false]
launch/talos_params.launch
- - simulation [default: false]
  - ns [default: linear_feedback_controller]
  - arm_left_control_type [default: no_control]
  - arm_right_control_type [default: no_control]
  - legs_control_type [default: inertia_shaping_effort_analytic_dob_control]
  - torso_control_type [default: inertia_shaping_effort_analytic_dob_control]
  - head_control_type [default: no_control]
  - head_local_joint_control_pkg [default: pal_local_joint_control]
  - wrists_control_type [default: no_control]
  - wrists_local_joint_control_pkg [default: pal_local_joint_control]
  - arm_left_local_joint_control_pkg [default: inertia_shaping_effort_control]
  - arm_left_local_joint_control_pkg [default: pal_local_joint_control]
  - arm_right_local_joint_control_pkg [default: inertia_shaping_effort_control]
  - arm_right_local_joint_control_pkg [default: pal_local_joint_control]
  - legs_local_joint_control_pkg [default: inertia_shaping_effort_control]
  - legs_local_joint_control_pkg [default: pal_local_joint_control]
  - torso_local_joint_control_pkg [default: inertia_shaping_effort_control]
  - torso_local_joint_control_pkg [default: pal_local_joint_control]

Messages

No message files found.

Services

No service files found

Plugins

No plugins found.

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