Add constraints to describe closed loops

.github/workflows/ros2.yaml

@@ -15,6 +15,7 @@ jobs:
     name: 'ROS 2 CI (${{ matrix.build_name }})'
     runs-on: ubuntu-24.04
     strategy:
+      fail-fast: false
       matrix:
         include:
           - build_name: 'source deps'

CHANGELOG.rst

@@ -2,6 +2,34 @@
 Changelog for package urdfdom
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+6.0.0 (2026-04-20)
+-----------
+* Support for URDF Specification 1.2
+    * Extend parsing of acceleration, deceleration and jerk limits from ``limit`` tag (`#212 <https://github.com/ros/urdfdom/issues/212>`_)
+    * Update default limits for the joint limits and safety limits (`#249 <https://github.com/ros/urdfdom/issues/249>`_)
+    * Add invalid data checks to the Geometry data (`#242 <https://github.com/ros/urdfdom/issues/242>`_)
+    * Require urdfdom_headers 3.0.0 (`#257 <https://github.com/ros/urdfdom/issues/257>`_)
+* Use URDF_MAJOR_VERSION for SOVERSION (`#248 <https://github.com/ros/urdfdom/issues/248>`_)
+* Contributors: Jose Luis Rivero, Sai Kishor Kothakota, Steve Peters
+
+5.1.2 (2026-04-18)
+-----------
+* Revert "Extend parsing of acceleration, deceleration and jerk limits from `limit` tag (`#212 <https://github.com/ros/urdfdom/issues/212>`_)"
+  This was a breaking change that will be released in 6.0.0
+* Contributors: Steve Peters
+
+5.1.1 (2026-04-15)
+------------------
+
+* Prevent CI from failing fast to allow all builds to complete (`#254 <https://github.com/ros/urdfdom/issues/254>`_)
+* Remove ``urdf_world/types.h`` deprecation (`#251 <https://github.com/ros/urdfdom/issues/251>`_)
+* Extend parsing of acceleration, deceleration and jerk limits from ``limit`` tag (`#212 <https://github.com/ros/urdfdom/issues/212>`_)
+* ROS 2 CI: build urdfdom_headers from source (`#246 <https://github.com/ros/urdfdom/issues/246>`_)
+* Disable system workflow because ``urdfdom_headers`` isn't available on Ubuntu 24.04 (`#240 <https://github.com/ros/urdfdom/issues/240>`_)
+* Fix ROS 2 CI workflow by updating Ubuntu version and checkout action (`#239 <https://github.com/ros/urdfdom/issues/239>`_)
+
+* Contributors: Alejandro Hernández Cordero, Sai Kishor Kothakota, Steve Peters
+
 5.1.0 (2026-02-06)
 ------------------
 * Support for URDF Specification 1.1

CMakeLists.txt

@@ -51,7 +51,7 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
 find_package(TinyXML2 REQUIRED)
 
-find_package(urdfdom_headers 2.1.0 REQUIRED)
+find_package(urdfdom_headers 3.0.0 REQUIRED)
 find_package(console_bridge_vendor QUIET) # Provides console_bridge 0.4.0 on platforms without it.
 find_package(console_bridge REQUIRED)
 

README.md

@@ -1,9 +1,16 @@
-urdfdom
-===========
+# urdfdom
 
-The URDF (U-Robot Description Format) library provides core data structures and a simple XML parsers for populating the class data structures from an URDF file.
+The URDF (U-Robot Description Format) library provides core data structures and simple XML parsers for populating the class data structures from a URDF file.
 
-For now, the details of the URDF specifications reside on http://ros.org/wiki/urdf
+Like the accompanying `urdfdom_headers`, this repository is a **custom fork** that includes an implementation of a C++ parser with specialized support for **constraint descriptions** to safely model closed-loop kinematics (e.g., for parallel robots).
+
+## Constraints Feature
+
+This fork introduces `constraint` elements representing "cut joints" or "cut links" allowing the description of closed kinematic loops without breaking surrounding packages.
+- It parses constraints exactly like the standard URDF `joint` element structure but includes a `child_frame` origin and a `child` axis to effectively describe the two frames of the cut element.
+- The constraint structure depends on the custom types (`UNKNOWN`, `REVOLUTE`, `PRISMATIC`, `UNIVERSAL`, `SPHERICAL`, and `LINK`).
+
+For now, the details of the general URDF specifications reside on http://ros.org/wiki/urdf
 
 ### Using with ROS
 
@@ -110,6 +117,13 @@ Version 1.2 extends the URDF specification with extended joint limits:
 - **Deceleration limit**: The `deceleration` attribute specifies the maximum joint deceleration
 - **Jerk limit**: The `jerk` attribute specifies the maximum joint jerk (rate of change of acceleration)
 
+Version 1.2 also relaxes some requirements on the existing joint limit attributes:
+- `lower` and `upper` are optional for non-`revolute`/non-`prismatic` joints and default to `-infinity` and `infinity` when omitted
+- for `revolute` and `prismatic` joints, both `lower` and `upper` must be provided
+- `effort` and `velocity` become optional and default to infinity when omitted
+- `effort`, `velocity`, `acceleration`, `deceleration`, and `jerk` must all be non-negative when provided
+- when both are specified, `upper` must be greater than or equal to `lower`
+
 All three attributes are optional and default to infinity (no limit). If `acceleration` is specified but `deceleration` is not, `deceleration` defaults to the acceleration value. All values must be non-negative.
 
 **Extended Joint Limits Example:**
@@ -132,6 +146,23 @@ All three attributes are optional and default to infinity (no limit). If `accele
 | `deceleration` | Maximum joint deceleration (rad/s² or m/s²) | Same as `acceleration`, or infinity if `acceleration` is not set | Must be non-negative |
 | `jerk` | Maximum joint jerk (rad/s³ or m/s³) | Infinity | Must be non-negative |
 
+#### Joint Limit Semantics By Version
+
+The parser keeps legacy behavior for older URDF versions and only applies the relaxed defaults starting in version 1.2.
+
+| Attribute | Version 1.0 / 1.1 | Version 1.2 |
+|-----------|-------------------|-------------|
+| `lower` | Optional, defaults to `0.0` when omitted | Optional for non-revolute/non-prismatic joints, defaults to `-infinity` when omitted |
+| `upper` | Optional, defaults to `0.0` when omitted | Optional for non-revolute/non-prismatic joints, defaults to `infinity` when omitted |
+| `effort` | Required, parsing fails if omitted | Optional, defaults to `infinity` when omitted |
+| `velocity` | Required, parsing fails if omitted | Optional, defaults to `infinity` when omitted |
+| `acceleration` | Ignored with warning if provided | Optional, defaults to `infinity` when omitted |
+| `deceleration` | Ignored with warning if provided | Optional, defaults to `acceleration` if set, otherwise infinity |
+| `jerk` | Ignored with warning if provided | Optional, defaults to `infinity` when omitted |
+
+For all supported versions, invalid numeric values still fail parsing. In version 1.2, negative values for `effort`, `velocity`, `acceleration`, `deceleration`, and `jerk` are rejected.
+In version 1.2, `revolute` and `prismatic` joints additionally require both `lower` and `upper`, and `upper` cannot be smaller than `lower`.
+
 #### Compatibility and Parsing Behavior
 
 | Scenario | Behavior |

package.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <package format="2">
   <name>urdfdom</name>
-  <version>5.1.0</version>
+  <version>6.0.0</version>
   <description>A library to access URDFs using the DOM model.</description>
 
   <maintainer email="clalancette@openrobotics.org">Chris Lalancette</maintainer>

urdf_parser/CMakeLists.txt

@@ -22,7 +22,8 @@ macro(add_urdfdom_library)
   endif()
   set_target_properties(${add_urdfdom_library_LIBNAME} PROPERTIES
     DEFINE_SYMBOL URDFDOM_EXPORTS
-    SOVERSION ${URDF_MAJOR_MINOR_VERSION})
+    SOVERSION ${URDF_MAJOR_VERSION}
+    VERSION ${URDF_VERSION})
 endmacro()
 
 if(TARGET console_bridge::console_bridge)
@@ -45,6 +46,7 @@ add_urdfdom_library(
     src/model.cpp
     src/link.cpp
     src/joint.cpp
+    src/constraint.cpp
     src/world.cpp)
 
 add_urdfdom_library(
@@ -54,6 +56,7 @@ add_urdfdom_library(
     src/pose.cpp
     src/model.cpp
     src/link.cpp
+    src/constraint.cpp
     src/joint.cpp)
 
 add_urdfdom_library(

urdf_parser/include/urdf_parser/urdf_parser.h

@@ -43,10 +43,11 @@
 #include <vector>
 
 #include <urdf_model/model.h>
+#include <urdf_model/constraint.h>
 #include <urdf_model/color.h>
 #include <urdf_model/utils.h>
 #include <urdf_sensor/sensor.h>
-#include <urdf_world/types.h>
+#include <urdf_model/types.h>
 
 #include "exportdecl.h"