The nav2_util package contains utilities abstracted from individual packages which may find use in other uses. Some examples of things you'll find here:

Geometry utilities for computing distances and values in paths
A Nav2 specific lifecycle node wrapper for boilerplate code and useful common utilities like declare_parameter_if_not_declared()
Simplified service clients
Simplified action servers
Transformation and robot pose helpers
Twist Subscriber and Twist Publisher

The long-term aim is for these utilities to find more permanent homes in other packages (within and outside of Nav2) or migrate to the raw tools made available in ROS 2.

Twist Publisher and Twist Subscriber for commanded velocities

Background

The Twist Publisher and Twist Subscriber are utility classes to assist NAV2 transition from Twist to TwistStamped.

Details on the migration are found in #1594.

Certain applications of NAV2, such as in ROS Aerial mandate the usage of TwistStamped, while many other applications still use Twist.

The utility has the following effect:

Allows use of either Twist or TwistStamped, controlled by ROS parameter enable_stamped_cmd_vel
Preserves existing topic names without duplication of data

Every node in nav2 that subscribes or publishes velocity commands with Twist now supports this optional behavior. The behavior up through ROS 2 Iron is preserved - using Twist. In a future ROS 2 version, when enough of the ROS ecosystem has moved to TwistStamped, the default may change.