Football Table Simulation Visualization Tool

Author: Erik Stoltenborg

Gazebo

A simulator is developed to easily test new algorithms without depending on the actual robot. In has been developed using gazebo (w/o the use of ROS), a so-called physics abstraction layer, which employs ODE combined with OGRE for rendering. Gazebo has been very well maintained since 2012, since it became the official simulator for the DARPA Robotics Challenge. The environment/robots are described in the SDF format, which is very simular to *.xml. It can be easily combined with CAD-files, in this case is combined with a Collada drawing for more complex geometry. A previous attempt was created using MORSE, however this was aborted because the poor tune-ability of the physics and limited options for communication.

The gazebo simulator for the semi-automated soccertable.

Synchronized Inter-process Communication

To date, Gazebo is mostly used in combination with [http://wiki.ros.org/ ROS. However using ROS plugins yields a lot of overhead, moreover the timers and communication provided there or not accurate enough to ensure an accurate casual link. Therefore a plug-in was created enabling fast light-weight inter-process communication, allowing to run simulation to be ran up to 20 times faster than real-time without loss of causality.

This simulation communicates with Matlab Simulink using Interprocess Communication (IPC) wrapper library for the POSIX libraries, the wrapper makes the use of shared memory more accesible and easy to use. It uses shared memory protected by mutexes and condition variables enabling a thread-safe, synchronized, causal communication between two processes e.g. Gazebo and Simulink. This allows us to use the Gazebo simulator as a plant in our simulink control loop. Moreover this wrapper library could be used for (safe) IPC between two arbitrary processes. More on this library, it's basic principles and how it is used can be found here.

Matlab Simulink

The Simulink side of things can be found in MOTION_test.mdl, this is not an external, but is ran in simulink itself in the regular way. The main window is shown below, the simulator part is the the gazebo sub-system. The motion-generation contains the reinforcement learning, attractor dynamics and constraints for the actions.

Main window of MOTION_test.mdl

Motion generation window MOTION_test.mdl

Most relevant settings regarding the actions and the reinforcement learning are set in their respective masks. In the mask of primitives_select.cpp you can set all the parameters described in this RL section.