rtt_gazebo_system

RTT Gazebo System

This package provides a Gazebo system plugin which initializes RTT in the Gazebo server process and overrides RTT's normal Time service using rtt_rosclock with Gazebo as a manual time source. This means that not only will RTT::os::TimeService report the simulated time, but also any TaskContext which uses an rtt_rosclock::SimClockActivity will be triggered at the appropriate period.

Design

Since systems in a simulated world are neither guaranteed nor likely to run in real-time, we override the normal RTT TimeService and update it at each Gazebo simulation step so that it is synchronized with Gazebo's simulation clock. This is done with the rtt_rosclock manual clock source.

However, without using a custom RTT Activity to run a component (i.e. running a component with the normal RTT::PeriodicActivity), that component will be scheduled based on the wall time.

Instead, components that are meant to run periodically and which should run in accordance with simulation time should be executed by an rtt_rosclock::SimClockActivity. Note that this requirement is different than the RTT::SimulationActivity, which runs as fast as possible.

Usage

Since this is a Gazebo system plugin, it needs to be passed by name to the invocation of the Gazebo server. When using gazebo_ros_pkgs this can be done with the following roslaunch markup (where $(arg world) is the path to your Gazebo world file):

<node name="gazebo" pkg="gazebo_ros" type="gzserver" respawn="false" output="screen"
      args="$(arg world) -s librtt_gazebo_system.so" />
``

See the example in `rtt_gazebo_examples` for more details.