Franka Lightweight Interface

This package is a lightweight interface to connect to the Franka Panda robot, receive its state and send torques commands to the internal controller. It is made to be system agnostic (not relying on a ROS installation) and uses a ZMQ based communication network from network interfaces, encoding state and command data using state_representation and clproto from control libraries.

The design philosophy is to have two asynchronous processes which communicate over a common protocol:

• A realtime robot control interface (referred to as the server)
• A control loop (referred to as the client)

The server runs a simple internal controller that broadcasts the robot state and listens to commands to forward to the robot. The client receives the robot state, calculates a desired control value in an asynchronous fashion, and then sends the command to the server.

Quick start

• Preprocess
• Installation
• Connecting to the robot
• Robot IPs
• Running the interface
• Examples
• Authors / Maintainers

Preprocess

The Franka robot requires a realtime kernel for the server process to work properly. To install one on your computer you can use a patched kernel following instructions here. Any kernel is working, but we recommend using one closed to the version currently installed on your computer. For example, on Ubuntu 18.04 a kernel v5.4.78 would work with the associated RT patch would work. Note that not all the available kernels are patched so be sure to select that have an associated RT patch available.

Installation

First, you will need to install state_representation and clproto from control libraries. The encoding library clproto also requires Google Protobuf to be installed.

# install control library state representation
git clone -b develop --depth 1 https://github.com/epfl-lasa/control-libraries
cd control-libraries/source
sudo ./install.sh --no-controllers --no-dynamical-systems --no-robot-model --auto

# install clproto protobuf bindings
cd ../../control-libraries/protocol
RUN sudo ./install.sh --auto

Secondly, install network_interfaces:

git clone -b develop --depth 1 https://github.com/aica-technology/network-interfaces
cd network-interfaces
sudo ./install.sh --no-python --auto

Then, make sure the submodule libfranka is available:

cd franka_lightweight_interface
git submodule init && git submodule update

Install libfranka

The building process relies on cmake. You first need to build and install libfranka following the recommendation from the website. First download the required packages:

sudo apt install build-essential cmake git libpoco-dev libeigen3-dev libtool

Then build and install the library

cd lib/libfranka && mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Release .. && make -j && sudo make install -j && sudo ldconfig

Build the interface

Finally, build the interface with:

cd franka_lightweight_interface
mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Release .. && make -j

Optionally, one can run sudo make install and sudo ldconfig to install the interface to /usr/local/bin.

Connecting to the robot

The robot proposes two type of connections using ethernet cables, one is connected to the control box and one directly to the robot. The latest is simply used to access the graphical interface to unlock the robot joints. For using the robot with this library, you should connect to the control box only.

Connect the control box ethernet cable and follow the instructions to set up the connection with the proper IP address. This is detailed on libfranka under Linux workstation network configuration.

You can then access the web interface that allows to unlock the joints of the robot on https://.

Robot IPs

There are currently two Franka Panda robots:

• Franka Papa, with IP 172.16.0.2 and ID 16
• Franka Quebec 17, with IP 172.17.0.2 and ID 17

Running the interface

To start the interface, first unlock the robot joints using the web interface. The LEDs on the robot change to blue. Then simply run the interface with your desired robot ID (either 16 or 17) and optionally a prefix that allows to set the robot name and joint names:

cd build && ./franka_lightweight_interface <robot-id> <robot-prefix>

In case the controller stops, due to violation of the velocities or efforts applied on the robot, you can push on the emergency stop button, which turns the LEDs to white and unlock it to bring it back to blue. The controller is automatically restarted to accept new commands.

Examples

See here for examples on how to use the interface to control the robot.

Authors / Maintainers

For any questions or further explanations, please contact the authors.

• Enrico Eberhard (enrico.eberhard@epfl.ch)
• Dominic Reber (dominic.reber@epfl.ch)
• Baptiste Busch (baptiste.busch@epfl.ch)