Universal Robots Client Library

Universal Robots Client Library

A C++ library for accessing Universal Robots interfaces. With this library C++-based drivers can be implemented in order to create external applications leveraging the versatility of Universal Robots robotic manipulators.

The library has no external dependencies besides the standard C++ libraries such as ROS, or boost to make it easy to integrate and maintain. It also serves as the foundation for the ROS and ROS 2 drivers.

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Requirements

• Polyscope (The software running on the robot controller) version 3.14.3 (for CB3-Series), or 5.9.4 (for e-Series) or 10.7.0 (For PolyScope X) or higher. If you use an older Polyscope version it is suggested to update your robot. If for some reason (please tell us in the issues why) you cannot upgrade your robot, please see the version compatibility table (opens in a new tab) for a compatible tag.
• The library requires an implementation of POSIX threads such as the pthread library

Build instructions

See Build / installation (opens in a new tab)

License

The majority of this library is licensed under the Apache-2.0 licensed. However, certain parts are licensed under different licenses:

• The queue used inside the communication structures is originally written by Cameron Desrochers and is released under the BSD-2-Clause license.
• The semaphore implementation used inside the queue implementation is written by Jeff Preshing and licensed under the zlib license

While the main LICENSE file in this repository contains the Apache-2.0 license used for the majority of the work, the respective libraries of third-party components reside together with the code imported from those third parties.

Library contents

Currently, this library contains the following components:

• Basic primary interface: The primary interface isn't fully implemented at the current state and provides only basic functionality. See A word on the primary / secondary interface for further information about the primary interface.
• RTDE interface: The RTDE interface (opens in a new tab) is fully supported by this library. See RTDEClient (opens in a new tab) for further information on how to use this library as an RTDE client.
• Dashboard interface: The Dashboard server (opens in a new tab) can be accessed directly from C++ through helper functions using this library.
• Custom motion streaming: This library was initially developed as part of the Universal Robots ROS driver (opens in a new tab). Therefore, it also contains a mechanism to do data streaming through a custom socket, e.g. to perform motion command streaming.

Example driver

In the examples subfolder you will find a minimal example of a running driver. It starts an instance of the UrDriver class and prints the RTDE values read from the controller. To run it make sure to

• have an instance of a robot controller / URSim running at the configured IP address (or adapt the address to your needs)
• run it from the package's main folder (the one where this README.md file is stored), as for simplicity reasons it doesn't use any sophisticated method to locate the required files.

Architecture

See Architecture documentation (opens in a new tab)

A word on the primary / secondary interface

Currently, this library doesn't support the primary interface very well, as the Universal Robots ROS driver (opens in a new tab) was built mainly upon the RTDE interface. The PrimaryClient for directly accessing the primary interface doesn't support all features of the primary interface.

The comm::URStream class can be used to open a connection to the primary / secondary interface and send data to it. The producer/consumer pipeline structure can also be used together with the primary / secondary interface. However, package parsing isn't implemented for most packages currently. See the primary_pipeline example (opens in a new tab) on details how to set this up. Note that when running this example, most packages will just be printed as their raw byte streams in a hex notation, as they aren't implemented in the library, yet.

A word on Real-Time scheduling

As mentioned above, for a clean operation it is quite critical that arriving RTDE messages are read before the next message arrives. Due to this, both, the RTDE receive thread and the thread calling getDataPackage() should be scheduled with real-time priority. See this guide (opens in a new tab) for details on how to set this up.

The RTDE receive thread will be scheduled to real-time priority automatically, if applicable. If this doesn't work, an error is raised at startup. The main thread calling getDataPackage should be scheduled to real-time priority by the application. See the ur_robot_driver (opens in a new tab) as an example.

Producer / Consumer architecture

Communication with the primary / secondary and RTDE interfaces is designed to use a consumer/producer pattern. The Producer reads data from the socket whenever it comes in, parses the contents and stores the parsed packages into a pipeline queue. You can write your own consumers that use the packages coming from the producer. See the comm::ShellConsumer (opens in a new tab) as an example.

Logging configuration

As this library was originally designed to be included into a ROS driver but also to be used as a standalone library, it uses custom logging macros instead of direct printf or std::cout statements.

The macro based interface is by default using the DefaultLogHandler (opens in a new tab) to print the logging messages as printf statements. It is possible to define your own log handler to change the behavior, see create new log handler on how to.

Change logging level

Make sure to set the logging level in your application, as by default only messages of level WARNING or higher will be printed. See below for an example:

#include "ur_client_library/log.h"

int main(int argc, char* argv[])
{
  urcl::setLogLevel(urcl::LogLevel::DEBUG);

  URCL_LOG_DEBUG("Logging debug message");
  return 0;
}

Create new log handler

The logger comes with an interface LogHandler (opens in a new tab), which can be used to implement your own log handler for messages logged with this library. This can be done by inheriting from the LogHandler class.

If you want to create a new log handler in your application, you can use below example as inspiration:

#include "ur_client_library/log.h"
#include <iostream>

class MyLogHandler : public urcl::LogHandler
{
public:
  MyLogHandler() = default;

  void log(const char* file, int line, urcl::LogLevel loglevel, const char* log) override
  {
    switch (loglevel)
    {
      case urcl::LogLevel::INFO:
        std::cout << "INFO " << file << " " << line << ": " << log << std::endl;
        break;
      case urcl::LogLevel::DEBUG:
        std::cout << "DEBUG " << file << " " << line << ": " << log << std::endl;
        break;
      case urcl::LogLevel::WARN:
        std::cout << "WARN " << file << " " << line << ": " << log << std::endl;
        break;
      case urcl::LogLevel::ERROR:
        std::cout << "ERROR " << file << " " << line << ": " << log << std::endl;
        break;
      case urcl::LogLevel::FATAL:
        std::cout << "ERROR " << file << " " << line << ": " << log << std::endl;
        break;
      default:
        break;
    }
  }
};

int main(int argc, char* argv[])
{
  urcl::setLogLevel(urcl::LogLevel::DEBUG);
  std::unique_ptr<MyLogHandler> log_handler(new MyLogHandler);
  urcl::registerLogHandler(std::move(log_handler));

  URCL_LOG_DEBUG("logging debug message");
  URCL_LOG_INFO("logging info message");
  return 0;
}

Contributor Guidelines

• This repo supports pre-commit (opens in a new tab) e.g. for automatic code formatting. TLDR: This will prevent you from committing falsely formatted code:

  pipx install pre-commit
  pre-commit install
  

• Succeeding pipelines are a must on Pull Requests (unless there is a reason, e.g. when there have been upstream changes).

• We try to increase and keep our code coverage high, so PRs with new features should also have tests covering them.

• Parameters of public methods must all be documented.

Acknowledgment

Many parts of this library are forked from the ur_modern_driver (opens in a new tab).

Developed in collaboration between:

(opens in a new tab)   and   (opens in a new tab).

(opens in a new tab)

Supported by ROSIN - ROS-Industrial Quality-Assured Robot Software Components. More information: rosin-project.eu (opens in a new tab)

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 732287.