KDL Parser (Standalone)

A standalone C++ library for converting URDF (Unified Robot Description Format) files to KDL (Kinematics and Dynamics Library) tree structures. This is a ROS-independent version that can be compiled and used on Windows, Linux, and macOS without any ROS dependencies.

Features

• ✅ ROS-free: Completely independent from ROS/ROS2, no ament_cmake, rcutils, or other ROS dependencies
• ✅ Cross-platform: Supports Windows, Linux, and macOS
• ✅ Pure CMake: Uses standard CMake build system (no ROS build tools required)
• ✅ C++17: Modern C++ standard support
• ✅ Lightweight: Minimal dependencies (only KDL, urdfdom, and Eigen3)

Requirements

• CMake >= 3.15
• C++17 compatible compiler (GCC 7+, Clang 5+, MSVC 2017+)
• Dependencies:
  • orocos-kdl - Kinematics and Dynamics Library
  • urdfdom - URDF parser library
  • Eigen3 - Linear algebra library

Installation

Windows (using vcpkg)

1. Install vcpkg if you haven't already:

   git clone https://github.com/microsoft/vcpkg.git
   cd vcpkg
   .\bootstrap-vcpkg.bat

2. Install dependencies:

   .\vcpkg install orocos-kdl:x64-windows
   .\vcpkg install urdfdom:x64-windows
   .\vcpkg install eigen3:x64-windows

3. Configure CMake with vcpkg toolchain:

   cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=[path-to-vcpkg]/scripts/buildsystems/vcpkg.cmake

Linux (Ubuntu/Debian)

sudo apt-get update
sudo apt-get install libeigen3-dev liborocos-kdl-dev liburdfdom-dev

macOS (using Homebrew)

brew install eigen orocos-kdl urdfdom

Building

Standard Build

# Configure
cmake -B build -S .

# Build
cmake --build build

# (Optional) Install
cmake --install build --prefix install

Build with Tests

The project includes a test program that can be enabled:

cmake -B build -S . -DBUILD_TEST=ON
cmake --build build

Windows (Visual Studio)

# Generate Visual Studio solution
cmake -B build -S . -G "Visual Studio 17 2022" -A x64

# Open kdl_parser.sln in Visual Studio or build from command line
cmake --build build --config Release

Usage

Basic Example

#include "kdl_parser/kdl_parser.hpp"
#include "kdl/tree.hpp"

int main() {
    KDL::Tree tree;
    
    // Parse URDF from file
    if (!kdl_parser::treeFromFile("robot.urdf", tree)) {
        std::cerr << "Failed to parse URDF file" << std::endl;
        return 1;
    }
    
    // Use the KDL tree for kinematics calculations
    // ...
    
    return 0;
}

Parse from String

std::string urdf_string = "<?xml version=\"1.0\"?>...";
KDL::Tree tree;
if (kdl_parser::treeFromString(urdf_string, tree)) {
    // Success
}

Parse from URDF Model

#include "urdf_model/model.h"
#include "urdf_parser/urdf_parser.h"

urdf::ModelInterfaceSharedPtr model = urdf::parseURDF(urdf_string);
KDL::Tree tree;
if (kdl_parser::treeFromUrdfModel(*model, tree)) {
    // Success
}

API Reference

The library provides three main functions in the kdl_parser namespace:

• bool treeFromFile(const std::string &file, KDL::Tree &tree) - Parse URDF from a file
• bool treeFromString(const std::string &xml, KDL::Tree &tree) - Parse URDF from a string
• bool treeFromUrdfModel(const urdf::ModelInterface &robot_model, KDL::Tree &tree) - Convert from URDF model object

All functions return true on success and false on failure.

Integration with Your Project

Using CMake

# Find the library
find_package(kdl_parser REQUIRED)

# Link to your target
target_link_libraries(your_target PRIVATE kdl_parser)

Manual Integration

1. Add include/ to your include paths
2. Link against the kdl_parser library
3. Ensure KDL, urdfdom, and Eigen3 are available

Differences from ROS Version

This standalone version differs from the original ROS kdl_parser package in the following ways:

• ❌ No ROS/ROS2 dependencies (ament_cmake, rcutils, etc.)
• ❌ No ROS-specific logging (uses standard C++ fprintf instead)
• ✅ Can be compiled independently on Windows without ROS
• ✅ Uses standard CMake instead of ament_cmake
• ✅ No package.xml required

The API is fully compatible with the ROS version, so existing code using kdl_parser should work without modification.

License

This project is licensed under the BSD 3-Clause License - see the LICENSE file for details.

Acknowledgments

This project is based on the original kdl_parser by Willow Garage, with all ROS dependencies removed to enable standalone usage.