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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 5 of 27
Figure 3. Combination of movement with different evasion intensities.
Figure 4. Virtual evasive force of moving targets.
2.2. Motion model of moving targets
As the motion law of the moving targets is unknown, it is assumed that the moving target has a maximum
movement distance of , and the motion of each target can be represented by a Gauss-Markov motion
[9]
model . The movement of each target in every motion cycle can be considered as a combination of random
movementanddirectionalevasivemovement. Figure3showsthemovementofthemovingtargetwithdifferent
evasion intensities.
In order to effectively evade the search of UAVs, a virtual evasive force is defined in this paper, which includes
two directions of evasion: away from the current position of the UAV and away from the forward path of the
UAV. Figure 4 shows the virtual evasive force of a moving target when facing the search for i-th UAV.
In Figure 4, F represents the virtual evasive force A to keep away from the current position of i-th UAV,
F represents the virtual evasive force B to keep away from the forward path of i-th UAV, and F represents
the comprehensive virtual evasive force of i-th UAV. Considering the distance from the target to the UAV, the
virtual evasive force A is defined as:
3
F = − ·e (1)
wheree istheunitdirectionvectorfromi-thUAVtothetarget, istheresponseamplitudeofvirtualevasive
force A, and is the corresponding straight response distance. Considering that the target cannot effectively
determine the flight direction and threat level of the UAV at a long distance, it is reasonable to assume that the
evasive force is negatively correlated with distance. The virtual evasive force B is defined as:
