Cooperative standoff tracking of target in non-wide area using multi-UAVs with optical cameras

In order to achieve the cooperative standoff tracking of target in non-wide area by multiple unmanned aerial vehicles (UAVs) with installed optical cameras, this paper proposes the constrained interacting multiple model (CIMM) filter to estimate the target state, as well as the time optimal guidance vector field (TOGVF) to optimize the UAV trajectory. Firstly, the geographical constraint equation deduced from the non-wide area is introduced into the traditional interacting multiple model, aiming to improve the estimation accuracy of the motion state of moving target measured from the optical cameras. According to the target motion information, the TOGVF method is then adopted to generate the velocity in the vertical plane guiding each UAV to the optimal observation height, as well as the velocity in the horizontal plane with which each UAV will converge to the standoff distance along the tangent of the limit cycle. On this basis, the speed of each UAV is adjusted in order to balance the phase difference and achieve the cooperation among multi-UAVs. The experimental results show that our method is effective in non-wide area. The estimation accuracy of target motion via CIMM increases by more than 30% compared to the single-model based filter, and the UAVs transfer to the limit cycle along the shortest path by TOGVF.