SERL Franka Controllers

Robot controller used in SERL (A Software Suite for Sample-Efficient Robotic Reinforcement Learning)

Serl Website and Paper: https://serl-robot.github.io/

serl_franka_controllers is a ROS package designed to control Franka Emika Robot through libfranka and franka_ros. This package provides a compliant yet accurate Cartesian Impedance Controller for safe online reinforcement learning algorithms, as well as a Joint Position Controller for resetting arm.

Compliance and accuracy is achieved at the same time by limiting the reference point of the Impedance controller to be within a certain distance from the current pose in the realtime loop. This way, a high gain can be used for accuracy without excess force when in contact.

Installation

Prerequisites

• ROS Noetic
• Installation of libfranka>=0.8.0 and franka_ros>=0.8.0 according to the Franka FCI Documentation

  sudo apt install ros-noetic-libfranka ros-noetic-franka-ros

Installing via apt-get

sudo apt-get install ros-serl_franka_controllers

Installing from Source

cd ~/catkin_ws/src
git clone git@github.com:rail-berkeley/serl_franka_controllers.git
cd ~/catkin_ws
catkin_make --pkg serl_franka_controllers
source ~/catkin_ws/devel/setup.bash

Realtime Constraint

The franka_ros requires a realtime kernel by default. This is not possible if you want to install CUDA on the same machine. A workaround is to ignore the realtime constraint in catkin_ws/src/franka_ros/franka_control/config/franka_control_node.yaml

realtime_config: ignore

Usage

Cartesian Impedance Controller

To launch the Cartesian Impedance Controller, use:

roslaunch serl_franka_controllers impedance.launch robot_ip:=<RobotIP> load_gripper:=<true/false>

Replace with the IP address of your Franka robot. The load_gripper argument is a boolean value (true or false) depending on whether you have a gripper attached.

Compliance parameters for the controller can be adjusted in an interactive GUI by running rosrun rqt_reconfigure rqt_reconfigure. This can also be achieved in Python code as demonstrated in the example section.

Joint Position Controller

For resetting or moving the robot to a specific joint position, launch the joint position controller:

rosparam set /target_joint_positions '[q1, q2, q3, q4, q5, q6, q7]'
roslaunch serl_franka_controllers joint.launch robot_ip:=<RobotIP> load_gripper:=<true/false>

Here, you also need to replace with the actual IP address and specify the load_gripper option. Then replace [q1, q2, q3, q4, q5, q6, q7] with the desired joint positions.

rospy Example

We include a requirements.txt and python script to show one way of interacting with the controller. This script shows how to adjust the reference limiting values and how to send robot commands through ROS Topics and dynamic_reconfigure. To use this, run

conda create -n serl_controller python=3.8
conda activate serl_controller
pip install -r requirements.txt
python test/test.py --robot_ip=ROBOT_IP