FRI-Client-SDK_Python

KUKA Fast Robot Interface Python SDK. The code in this repository, provides Python bindings for the FRI Client SDK C++. The interface has been designed to be as similar as possible to the documentation provided by KUKA.

There is one difference users of the Python bindings should be aware. When instantiating the client application, in C++ this is performed as follows.

// ..setup client..

// create new udp connection
UdpConnection connection;


// pass connection and client to a new FRI client application
ClientApplication app(connection, client);

In Python, the equivalent code is as follows.

import pyFRI as fri

# ..setup client..

app = fri.ClientApplication(client)

Since UDP is the only supported connection type and the connection object is not actually required by the user after declaring the variable, the UdpConnection object is created internally to the fri.ClientApplication class object.

See the examples.

Important notice

THIS IS NOT A KUKA PRODUCT.

@cmower is not affiliated with KUKA.

Support

The following versions of FRI are currently supported:

• 1.15
• 2.5

Note, whilst FRI version 2.5 is supported some functionality is not. Currently, FRI Cartesian Overlay is not supported by FRI-Client-SDK_Python.

If you have a different version, please consider forking and submitting a pull request.

Install

1. Clone repository: $ git clone --recursive git@github.com:cmower/FRI-Client-SDK_Python.git (make sure you include --recursive)
2. Change directory: $ cd FRI-Client-SDK_Python
3. Modify fri_config.py: uncomment the line corresponding to your version of FRI.
4. Install: $ pip install .

Upgrading/switching between FRI Versions

If you upgrade your FRI version or want to switch between them, you need to manually remove the FRI-Client-SDK_Python/build directory before running pip install.

Usage

Java application

A flexible Java application is provided here. This must be installed on the KUKA Sunrise controller.

Data types

You can pass NumPy arrays to the "set" methods (e.g. setJointPosition) in order to command the robot. However, you must ensure the format of the array is correct.

Arrays that have a dtype of np.float32 are the only ones that can be accepted. See how the commands are set in the the examples.

Collecting data from the robot

We provide additional functionality to the LBR client application class that enables data collection to a text file. In Python, simply add the following

app = fri.ClientApplication(client)
app.collect_data(file_name)

The string file_name should contain the file name for the data file. We use the comma-separated values format for the data file, and so the file name should end with the extension .csv - note, if this isn't the case then .csv is automatically appended to the given file name.

The columns in the recorded csv file are as follows:

• index: the index of the recorded data, starts at 0, and is incremented by 1 at each call to the step method.
• time: the time of the command, starts at 0.0, then is incremented by the sample time at each call to the step method.
• record_time_nsec: the epoch time collected when the data in the current time step is recorded.
• tsec: controller time as specified by the FRI in seconds. See FRI documentation for getTimestampSec.
• tnsec: controller time as specified by the FRI in nanoseconds. See FRI documentation for getTimestampNanoSec.
• mp1, ..., mp7: The measured joint position for the robot.
• ip1, ..., ip7: The ipo joint position for the robot.
• mt1, ..., mt7: The measured torque for the robot.
• et1, ..., et7: The external torque for the robot.
• dt: The sample time specified on the KUKA controller.

See the examples/LBRJointSineOverlay.py example that demonstrates how to easily collect data from the robot.

Examples

First, ensure the corresponding Java applications for each example are installed (these were supplied with KUKA Sunrise). Then turn on the robot, connect your laptop via ethernet, and follow these steps on your laptop.

1. Change directory: cd /path/to/FRI-Client-SDK_Python/examples
2. Run examples
   • $ python LBRJointSineOverlay.py # based on examples provided by KUKA
   • $ python LBRTorqueSineOverlay.py # based on examples provided by KUKA
   • $ python LBRWrenchSineOverlay.py # based on examples provided by KUKA
   • $ python joint_teleop.py
   • $ python task_teleop.py

Documentation

You can find documentation for pyFRI in the wiki.

Citation

If you enjoyed using this repository for your work, we would really appreciate ❤️ if you could cite it, as it helps us to continue offering support.

@misc{huber2023lbrstack,
      title={LBR-Stack: ROS 2 and Python Integration of KUKA FRI for Med and IIWA Robots}, 
      author={Martin Huber and Christopher E. Mower and Sebastien Ourselin and Tom Vercauteren and Christos Bergeles},
      year={2023},
      eprint={2311.12709},
      archivePrefix={arXiv},
      primaryClass={cs.RO}
}