# A Systematic Review of Perception System and Simulators for Autonomous Vehicles Research
## 5 Simulation
### Robotics Simulators
Gazebo has a modular design that allows different physics engines to be used, along with high-quality graphics, sensor models, and the creation of 3D worlds and graphical interfaces. Gazebo is built on top of the rendering engine Ogre3D to provide more realistic environments. The use of plugins expands the capabilities of Gazebo to include abilities such as dynamic loading of custom models and the use of stereo cameras, LiDAR, GPS, IMU or RADAR sensors. Being an open source product, there is a large and active robot community supporting and improving the product. One of the advantages of Gazebo is that it is already included in the ROS bundle. Gazebo is informally part of the ROS, a set of libraries and open source software tools that allow the user to create a robotic application. ROS and Gazebo are becoming more popular for the development of AVs. There have been a multitude of studies designing methods for validating the physics and sensor simulations of Gazebo; for example, in the latest edition of ROSCon Conference [84], BMW presented several works [85; 86] that focus on the simulation of autonomous vehicles. The TSC prototype Basic Autonomous Control Systems (B-ACS) for the LUTZ pods has been developed using ROS and simulated using Gazebo. The robot simulator V-REP [81], with an integrated development environment, is based on a distributed control architecture. Each object/model can be individually controlled via an embedded script, a plugin, a ROS or BlueZero node, a remote API client, or a custom solution. This makes V-REP very versatile and ideal for multi-robot applications. Controllers can be written in C/C++, Python, Java, Lua, Matlab or Octave. Webots is a commercial robot simulator developed by Cyberbotics used in more than 800 universities and research centers worldwide. It has reached a fairly stable state and supports a wide range of hardware. Webots makes use of ODE (Open Dynamics Engine) for the detection of collisions and dynamic simulation of the rigid body. The ODE library allows the physics of the objects to be simulated. Note that the physics plugins can be programmed only in C or C++. The software also provides a large collection of sensors, including a distance sensor, light sensor, cameras, LiDARs, GPS, accelerometer, and force-sensor. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Simulator Platforms** & **License** & **Simulation Engine** & **Graphical Engine** & **External Agent** \\ \hline Gazebo & GPL/Open Source & ODE, Bullet, & & Ogre3D & Yes \\  & GPL/Open Source, & ODE, Bullet, Vortex & OpenGL & Yes \\ Webots & Commercial & ODE & - & Yes \\ MRDS & Commercial & PhysX & DirectX & No \\ USARSim & GPL & Unreal Engine & Karma & Yes \\ BlenSor & GPL/Open Source & - & OpenGL & No \\ MORSE & GPL/Open Source & Blender, Bullet & OpenGL & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the main features of robotic simulator platforms for AVs. Microsoft Robotics Developer Studio (MRDS) is a Windows-based robotics platform from Microsoft Company using.NET based technology. It features visual programming, web and windows-based interfaces, 3D simulation with advanced physics, as well as easy access to robot's sensors and actuators in a number of languages. In addition to providing support for Microsoft Visual Studio 2010, Microsoft Robotics Developer Studio 4 provides a Visual Programming Language (VPL), which allows developers to create applications simply by dragging and dropping components onto a canvas and wiring them together. Princeton University's DARPA Urban Grand Challenge Autonomous Car [87] was programmed with MRDS. It is oriented towards educational projects with a low degree of complexity. Apart from robotic simulation platforms, there are other simulators in the robotic domain, which are relevant for research. Among them are USARSim [88], BlenSor [72] and MORSE [89]. USARSim is a free simulator based on the cross platform Unneal Engine. It was released under the GPL license, physics is simulated using the Karma Physics.