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Wang et al. Intell Robot 2023;3(4):538-64 I http://dx.doi.org/10.20517/ir.2023.30 Page 25 of 27

Figure 16. Comparison of the search results using different search methods.

Table 8. Average number of targets found using different search methods at simulation step = 100 without any prior information of the
probability distribution of target position
= 3 = 6
Number of targets
Greedy search Parallel search CSMTPE Greedy search Parallel search CSMTPE
= 1 0.38 0.58 0.73 —
= 2 0.95 1.23 1.35 1.20 1.43 1.53
= 3 — 1.53 1.95 2.15
= 4 — 2.25 2.53 2.68

less than that of CSMTPE at simulation step = 25, reflecting that it wasted more search steps due to blind
search in the early stage of the search, while the number of targets found in parallel search method is related
to the target distribution, resulting the poor search efficiency. In contrast, the CSMTPE proposed in this
paper continuously updates various search information maps to obtain more target information and takes into
account both short-term and long-term search efficiency when planning search paths.

Considering the existence of situations where the prior information of the target is unknown, the original
problem will degenerate into a covering search problem. Under this circumstance, another similar experiment
is conducted, and the search results are shown in Table 8.

When the prior information of the target is unknown, the search results reflect the conclusion that the search
efficiency ofCSMTPE will degenerateinto the level of that using theparallel search method. Meanwhile, it also
shows that the greedy search method performs significantly worse compared to other search methods above
due to the lack of long-term predictability. In summary, it proves that CSMTPE can adaptively and effectively
solve the multi-UAV regional cooperative search problem.

7. CONCLUSIONS
This paper addresses a challenging multi-UAV regional cooperative search problem for targets with the ability
to perceive and evade. In this scenario, moving targets can detect the presence of UAVs and take evasive
actions based on the UAVs’ motion patterns, increasing the difficulty of target search. To solve this problem,
we propose a novel search method called the CSMTPE for multi-UAV.

Firstly, we defined the motion model of such targets and design various search information maps and their