# Design and Implementation of Simulation System for Multi-UAV Mission
## 1 Introduction  
UAVs have the advantages of flexible deployment, ease of maintenance and operation, and simple take-off and landing requirements. They can be used in civilian application areas such as urban logistics [1], aerial photography [2], line inspection [3, 4], etc. ; in wartime, they can also be used for ground reconnaissance [5, 6, 7, 8, 9], strike missions [10, 11, 12, 13, 14, 15, 16, 17], dynamic target tracking, and other military tasks. However, a single UAV has many shortcomings in performing complex missions limited by its load and power constraints. If multiple UAVs with different functions are coordinated according to a relevant logic to give them a certain degree of autonomy and intelligence, the effect of mission accomplishment can be greatly improved. This is also one of the current hot research problems in the field of automation and artificial intelligence [18, 19, 20, 21, 22, 23]. In the multi-UAV research field, collaborative mission verification and testing plays an important role. Common verification methods include traditional numerical simulations [24, 25], hardware-in-the-loop simulations [26, 27], and real flight tests [28]. The numerical simulation is performed using MATLAB and other software, and the model is solved by constructing mathematical models and writing relevant algorithms on a computer basis. Finally, the calculated data and change curves of the simulation object are obtained. Hardware-in-the-loop simulation refers to the real-time simulation in which part of the physical objects are included in the simulation loop. Compared to numerical simulation, hardware-in-the-loop simulation is closer to real flight results. However, the hardware-in-the-loop simulation system for multi-UAV missions is more complex to build, which may result in longer test cycles and higher equipment costs. Real flight testing is the most direct and effective method of verifying multi-UAV missions. For example, the U.S.  
Office of Strategic Capabilities has conducted 103 UAVs with independent decision-making and online formation flight demonstrations [29], and the China Electronics Technology Group has also conducted 67, 119, and 200 fixed-wing UAV flight tests in recent years [30]. However, there are many risk points in real flight testing of multi-UAV missions, specifically the high property damage caused by hardware and software problems, the accidental injuries to personnel caused by UAV failures or human operator errors, and the increased development time and cost because of frequent test flights. Therefore, in the algorithm research and verification phase, a simulation test is more feasible than a real flight. One of the problems that should be solved by UAV simulation is how to make the theoretical results, including algorithms, a technical application value, especially to support verification in real flight. Researchers have achieved many results in studying the simulation of UAV missions. In [31], the simulation tool JADE is used to test large multi-UAV systems, and the use of the simulation environment and tools in agent communications is described. In [32], PixHawk flight control and peripherals are used to evaluate a LIDAR sensor and its ability to navigate and avoid obstacles. In [33], an interactive simulation platform for a UAV swarm based on MATLAB/Simulink is developed. It can realize 3D simulation visualization of UAVs and human-computer interaction functions such as voice and gestures. In [34], a modular co-formation software system for a UAV swarm is designed, and it is applicable for engineering practice. Currently, the multi-UAV mission simulation platform has some shortcomings, which are mainly reflected in the singularity of the function; it contains:  
1. Programs written with software such as MATLAB are mainly used to test the algorithms themselves, with insufficient attention paid to technical implementation. 2. Open-source simulation software such as FlightGear focuses on flight operations training, leaving autonomy and intelligence to be desired. 3.