SwarmSimX

One research interest of the Autonomous Robotics and Human-Machine Systems group at the Max Planck Institute for Biological Cybernetics is the human-in-the-loop bilateral control of a swarm of robots. The human operator may be presented with multiple feedback cues, e.g., visual, vestibular, haptic, auditive or even olfactory stimuli. The goal is to find a general methodology on how to best control multiple robots in a remote environment.

Software frameworks simulating a virtual environment are indispensable for this research work. Being able to access all information of an experiment setup is important to gain insights that may prove difficult or impossible to gain otherwise. Furthermore, hardware-in-the-loop and human-in-the-loop scenarios depend on software that is capable of performing calculations in real-time. A process running in simulation must proceed with the same pace as the process in reality.

Software suites capable of simulating multiple robots already exist and are widely used in research. Nonetheless, finding software that meets all requirements, i.e., real-time execution, realistic, exchangeable visual and physical representation, extendable software architecture and full control over inherent information of all simulated robots is a difficult task.

SwarmSimX (SSX) is capable of simulating both the visual and physical properties of robots acting in a user-defined environment in real-time. The software architecture allows for an easy exchange of the underlying libraries used for simulation. Shared modules may be loaded at runtime, extending the simulation with new functionality, without the need of recompiling the whole simulation environment.

Software architecture

The simulation environment can be divided into three main parts. Those parts are the visual representation, physical representation and the creation part. The following figure gives an overview of the elements used in the simulation and how they are related. In the nomenclature of SSX, the visual representation is managed by the RenderEngineRenderNodes are used to define individual elements of the RenderEngine. In a symmetric way the physical representation is managed by the PhysicEngine and the individual parts are calledPhysicNode. Both, Physic- and RenderNodes can be connected to form tree structures. Child nodes are defined (i.e., represented by position, orientation, mass, etc.) w.r.t. to the parent node to which they are connected.


SwarmSimX Software Architecture Overview
 The visual and physical representations are related to each other, as the physical representation is used to perform the actual simulation and the visual displays the behaviour of the objects being simulated. This relationship is expressed in the parallel structure of the design layout. At every timestep of the simulation the execution of logical modules is triggered. These modules can perform any kind of calculation and are used to extend the simulation with custom logic or custom functionality. They are called Driver and Sensor.

Drivers represent the behaviour of objects within the simulation environment. E.g. a Driver can represent the attitude controller of a Unmanned Arial Vehicle (UAV) flying in simulation that receives desired angles and adds forces/torques to the physical object being controlled. Another example is the logical module of an automated door that opens whenever an object moves within a certain range and closes after 5 s with no sensor input.

Sensors are used whenever information of objects within the simulation or the simulation itself needs to be retrieved. E.g. a sensor could emulate the expected values of a real sensor. This way a control algorithm implemented for a real microcontroller can be used with this sensor output, without modifying the code or the algorithm of the microcontroller code. Also omnipotent sensors can be implemented that measure the state of all simulated robots in the simulation. This kind of sensor may not exist in reality, but may prove helpful while developing new algorithms.

All those parts are stored together into a single object called Artifact. An Artifact may consist of multiple RenderNodes and PhysicNodes. Sensors and a Driver are not mandatory. It is possible to simulate several different Artifacts simultaneously. Artifacts state the main concept of SwarmSimX. Everything that can be placed in the simulation environment is defined as an Artifact.

Media

Flight of a simulated quadrotor following a given trajectory indicated by a red ball. In the first part of the video additional debug information (e.g., the reference frame of quadrotor) is visible.

References

Johannes Lächele, Development of a Real-Time Simulation Environment for multiple Robot Systems, diploma thesis, Eberhard Karls Universität Tübingen, October 2011.

Citation

If you want to refer to my work, please use the following citation.

@INCOLLECTION{Lachele2012,
author = {Johannes L{\"a}chele and Antonio Franchi and {Heinrich H.} B{\"u}lthoff and {Paolo Robuffo} Giordano},
title = {SwarmSimX: Real-time simulation environment for multi-robot systems},
booktitle = {Simulation, modeling, and programming for autonomous robots},
publisher = {Springer},
year = {2012},
pages = {375--387},
url = {http://laechele.eu/swarmsimx/}
}

 

2 thoughts on “SwarmSimX”

  1. Dear Lachele,

    I hope you are fine. Thank you for sharing such useful information on your blog. I am also PhD student here in Japan, working on Swarm robotics. I am interested to install SwarmSimX SSX.

    From your paper, I tried the given link to download the copy of SSX, but could not .. Please guide or share the alternative link to get a copy of SSX.

    Thanking you.

    IRFAN
    Ishikawa, Japan

    1. Dear Muhammad,

      I am happy you find the information useful and want to install and try SwarmSimX (SSX). Although I gained a lot creating SSX and it proved to be useful in many aspects, I have to inform you that I no longer work on SSX.

      Therefore, you will be mostly on your own to get it running/using it and I highly suggest going a different route, which is using a Game engine like Unity3D. Unity3D is free of charge and has many advantages, like NVIDIA PhysX, supports a lot of different operating systems and many more. The Unreal engine may also be a solution for you.
      If you still want to try SSX, you can follow the mini-howto on how to install it below.

      SSX can be obtained by checking out a subversion repository. The repository can be checkout out for free with the command:
      svn co https://svn.kyb.mpg.de/kyb-robotics
      There is a lot of documentation available from google on the details of subversion.

      The examples in the repository are heavily based on the robot operating system (ROS) and you will have to install it before you are able to run any examples. Please see the documentation on the ROS website for instructions on how to install it. I suggest installing ROS on a Ubuntu linux system, as all software is precompiled and very easy to install and maintain.

      The examples can be installed by first configuring your system correctly. You will need to adjust the system variable ROS_PACKAGE_PATH so that it includes the path to the stacks folder of SSX. The folder can be found in the ./kyb-robotics/SwarmSimX/trunk/stacks.
      As an example the package path can be configured temporarily with
      export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:/home/[username]/kyb-robotics/SwarmSimX/trunk/stacks
      assuming that the kyb-robotics repository is installed in your home folder and [username] is replaced with your system username.

      After that you should be able to compile/install the following example by typing
      rosmake massive_quadrotors
      It should take quite some time as it needs to install several software packages, so this is a good time for coffee/tea 🙂

      Finally, after all is completed successfully you should be able to run the massive_quadrotors example with
      roslaunch massive_quadrotors massive_robots

      This is a very short tutorial to get you started. There are lots of excellent webpages about ROS and subversion that provide you with detailed information, in case you run into issues. If you have any problems running SSX, let me know. I will try to answer as good as I can.

      All the best and good luck
      Johannes

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