# Real-time Conflict Resolution Algorithm for Multi-UAV Based on Model Predict Control
## 5 Simulation Results and Analysis  
To verify the performance of the discussed conflict resolution algorithm, numerical simulation results and analysis are presented in this section. The whole simulation system and the UAV objects  
Figure 8: Flow chart of the conflict resolution algorithm.  
were built using Visual C++ (ver. 10.0), and the results figures were created using MATLAB. The entire simulation was performed on a workstation consisting of a 3.5 GHz Intel Core-i7 CPU and 16 GB of physical RAM running 64-bit Microsoft Windows 10. The sampling interval \(\Delta t\) of DNMPC is set as 1 s, the maximum iteration step is set as 200, while the prediction time domain is set as 10 steps. The formulation and parameters tuning method are referred to the traditional form of DMC mentioned in Refs. [25; 26]. It is assumed that the UAVs obtain their state information completely accurately, that is, the status acquired by the UAVs at the current time in the simulations is equal to the current status of the calculation output of DNMPC at the previous time.  
Simulation 1: 3 cruising UAVs rendezvous, requiring conflict resolution. Supposing that all 3 UAVs have the same characteristics of flight, the initial conditions and other simulation parameters are listed as Table 1. The safe distance \(r_{safe}\) = 3 km and detection distance \(r_{dec}\) = 8 km. Since the UAVs are cruising, their velocities remain constant, and the synergetic heading angle control rule is used in this simulation. In this simulation, the maximum and average cycling time of DNMPC is 0.47 s and 0.31 s, respectively, which is less than \(\Delta t=1  
According to the initial conditions, the potential conflicts are detected as (UAV1-3,69s) and (UAV2-3,72s), which are within one prediction time domain. Thus, the DNMPC deals with the 3 UAVs in one conflict group, and UAV3 has the highest level due to its flight state. It is shown in Figures 9 and 11 that UAV3 flies past the conflict area and straight towards its destination, while UAV1 and UAV2 adjust their flight trajectories based on the synergetic heading angle control rule. Figure 10 shows that the distances between each of the UAVs are above the safe distance, which indicates that the adjustment plan calculated by DNMPC resolves potential conflicts sufficiently, and causes no further conflicts.  
Simulation 2: Conflict resolution of 4 UAVs. In this simulation, the safe distance \(r_{safe}=3\) km and the detection distance \(r_{dec}=15\) km. The initial conditions and other simulation parameters are listed as Table 2, and the other settings of DNMPC is the same as in Simulation 1. In this simulation, the maximum and average cycling times of DNMPC are 0.66 s and  
The simulation results show that, according to the initial conditions, conflict occurs between each pair of UAVs. Thus, DNMPC manages all conflict UAVs into two conflicts groups: (UAV2-3,76s) and (UAV1-4,89s) based on the proposed resolution rule, and resolves the conflicts separately. It is shown in Figures 12 and 13 that the potential conflicts are resolved sufficiently and without any further conflicts.  
To further demonstrate the merits of the proposed algorithm, regarding the conditions of Simulation 2, 150 Monte-Carlo simulations were carried out for comparison between the proposed method (denoted as A) and the method of Ref. [15] (denoted as B). Both methods were implemented under the same simulation settings. The following statistic indexes are listed in Table 3 for comparison: final performance indicator of equation (10) (FPI), total running time (TRT), and total number of further conflicts (TFC).  
It is shown in Table 3 that the final performance indicator of the proposed method is better than B. Also, the proposed method resolved the problem in less time and caused much less further conflict than B, which indicates that the proposed method enjoys superiority in terms of effectiveness and computation efficiency compared with common methods.