KUKA LBR Cartesian Impedance Control

A repository for controlling the KUKA lbr or med with cartesian impedance control.

ROS2 Distro	Controller	FRI library	LBR Stack
Humble
Jazzy

Setup

Set the FRI impedance gains to zero

Follows the instructions reported in the lbr stack documentation that you can find here.
Set the stiffness of the JointImpedanceControlMode in the LBRServer.java to zero for each joint, i.e.:

control_mode_ = new JointImpedanceControlMode(0, 0, 0, 0, 0, 0, 0);

Then synchronize the application to update the changes.

Install

Clone this repo inside your ros2 workspace as the src folder

git clone --recursive [email protected]:idra-lab/kuka_impedance.git src

Install ros2 dependencies

rosdep install --from-paths src -i -r -y

Build the workspace

colcon build --symlink-install

Run the controllers on real hardware

Gravity compensation

source install/setup.bash
ros2 launch lbr_bringup hardware.launch.py ctrl:=gravity_compensation

---

Cartesian impedance control

source install/setup.bash
ros2 launch lbr_bringup hardware.launch.py ctrl:=cartesian_impedance_controller model:=iiwa14 # or iiwa7, med7, med14

---

Cartesian impedance control with nullspace task

This controller takes the initial configuration as the reference position for the nullspace control.
Can be activated by setting

...
nullspace_stiffness: 10.0
...

in lbr_fri_ros2_stack/lbr_description/ros2_control/lbr_controllers.yaml under the cartesian_impedance_controller configuration.
Then run the controller:

source install/setup.bash
ros2 launch lbr_bringup hardware.launch.py ctrl:=cartesian_impedance_controller model:=iiwa14 # or iiwa7, med7, med14

---

Test the controllers in Gazebo

You need first to set

...
kuka_hw: false
...
compensate_gravity: true
compensate_coriolis: true

in lbr_fri_ros2_stack/lbr_description/ros2_control/lbr_controllers.yaml under the cartesian_impedance_controller configuration.
Then run the gazebo simulation:

source install/setup.bash
ros2 launch lbr_bringup gazebo.launch.py ctrl:=cartesian_impedance_controller model:=iiwa14

Tracking a reference trajectory

This controller takes a trajectory as input a PoseStamped message and tracks it. You need to publish a PoseStamped message on the /lbr/target_frame topic.
Some examples trajectories are already implemented here where tracking performances are also visualized.

git clone [email protected]:Hydran00/controller_evaluation.git
cd controller_evaluation/

Make sure that the robot type is set to "kuka" in the initialize.py file. Adjust the trajectory parameters in the traj_sin.py or traj_lin.py file. Then run the trajectory publisher:

source /opt/ros/humble/setup.bash
python3 traj_sin.py # traj_lin.py

References

• Cartesian controllers
• lbr ROS2 stack