# Building a Realistic Virtual Simulator for Unmanned Aerial Vehicle Teleoperation
### About the Proposal  
As observed in the previous survey, several simulators are dedicated to obtaining a UAV model to perform tasks such as route planning, adjusting controllers, or analyzing interactions with other vehicles. Some of these models aim to be realistic, i.e., the simulations generate numerical information that accurately describes the behavior of real-world UAVs. However, in most cases, the results of the simulations are limited to presenting numerical evidence.  
Concerning the above, other elements, besides an accurate numerical simulation, can contribute to developing a more realistic simulator, e.g., the development of a detailed virtual environment or an optimized interaction with the pilot. In this sense, few simulators show this information more naturally for humans, e.g., through a virtual 3D representation. Another interesting finding is the lack of simulators that consider a remote operation carried out by humans. As mentioned before, these are essential tools for pilot training.  
In the case of the advanced simulators (i.e., DJI Flight Simulator, Gazebo, and AirSim), some of the problems mentioned above seem to be solved. However, these have some drawbacks. For example, the main issue with the DJI Flight Simulator is that it is proprietary software, which means that the simulated UAVs and teleoperation devices are limited and cannot be extended. In addition, it is impossible to determine the details of its physics engine, which limits the possibility of extending or using it in tasks such as the design of control systems. Regarding Gazebo, the drawbacks are related to the dependence on third-party physics engines such as ODE, Simbody, Bullet, and DART. This dependence limits the numerical methods to solve the dynamics of UAVs and leads to the lack of an explicit model to carry out other essential tasks such as identification or controller tuning. Additionally, AirSim includes a simplified physics engine that does not support fixed-step-size simulations. This engine is excellent for speeding up the response times of the simulation, but it is not a good option when a faithful description of the physics involved in the operation of a UAV is required. Finally, it is important to remark that all the above alternatives are dependent on specific development technologies and platforms, which also reduces the availability of simulators for a part of the final users.  
Because of the above, this work proposes a framework for building realistic virtual simulators for the human operation of unmanned aerial vehicles, using the quadrotor as the study case. A detailed dynamic model of this UAV is obtained first to perform dynamic simulations. Then, a virtual 3D representation of the quadrotor and its operating environment is developed in Unity 3D. After that, the model, its dynamic simulation, and the virtual elements are coupled to obtain a virtual quadrotor simulation. Therefore, a teleoperation algorithm is proposed and included in the above simulation. This algorithm allows interactions between the human pilot and the UAV through a typical gamepad. Finally, the simulation is endowed with realism through meta-heuristic optimization, where the flight information obtained from a real quadrotor is used to tune the parameters of the teleoperation algorithm.  
The rest of this paper is organized as follows. The development of the quadrotor simulator is described in Section 2. The simulator is tested, and the results are presented in Section 3. Finally, Section 4 draws conclusions and details the future work.