This article investigates a distributed game strategy for formation control of multispacecraft subjected to nonlinear dynamics and J ₂ perturbations. In the proposed problem, each spacecraft is devoted to minimize its own performance cost using only local information, whereas the overall formation system attempts to seek an optimized decision based on communication topology. Therefore, in our scheme, the formation control problem can be treated using a Nash strategy. A worst case Nash strategy is proposed against the disturbance defined as a player, and we prove rigorously that an open-loop Nash equilibrium exists in the underlying problem. Then, a distributed terminal state observer is introduced to facilitate the local implementation of the proposed Nash strategy. Simulation results verified the performance of the proposed scheme.

This paper proposes a bio-inspired algorithm called virtual motion camouflage (VMC) to reduce the dimension and computational cost of entry trajectory optimization problem for the reusable launch vehicle. In the VMC framework, the trajectory to be planned can be obtained by predefining the virtual prey motion according to the boundary conditions, then optimizing the reference point and path control parameters using sequential quadratic programming algorithm. Compared with Gauss pseudospectral method, due to the proposed approach reduce the number of discrete points and the equality constraints of the optimization model, it can improve the convergence speed and reduce computational cost effectively. Two minimum time entry examples, without and with no-fly-zone constraints, are presented to demonstrate the effectiveness of the proposed approach.

Estimation of the time-difference-of-arrival (TDOA) between a signal and its time-shifted version has many applications, mostly in localization. Because compressive sensing (CS) can reduce the sampling rate and data volume, TDOA estimation from CS samples (CS-TDOA) has become a subject of interest. Generally, CS-TDOA has lower estimation accuracy and the Cramer-Rao bound (CRB) can quantify this degradation. The first part of this correspondence derives the CRB for CSTDOA estimation. In the second part, it proposes an incoherent processing scheme for CS-TDOA estimation using partial Fourier coefficients. It has the advantage of reducing the number of sampling channels needed to acquire those coefficients. Simulation results are given to corroborate the theoretical development.

This paper investigates a practical formation control problem of multi-satellite system, in which a group of small satellites are required to reach and maintain a desired geometric configuration under communication and measurement constraints. Toward this goal, we consider each satellite uses its local coordinate systems and senses its neighboring satellites to obtain angle measurements. A formation control scheme using only the angle measurements is proposed to form the desired configurations. Moreover, the triangular and polygonal configuration cases are developed, in which the sum of interior angles of polygons is utilized to guarantee the stability of the determined final configuration. In particular, motivated by formation rigidity principles which mean that satellites' formation is seen as a multi-point framework which need to be rigid to guarantee the uniqueness of the shape, we propose a formation determination approach to construct a rigid square configuration, and proves that, compared with existing schemes, the absolute position of each satellite and the knowledge of the communication topology are not needed for the proposed formation control law. Moreover, since the angle measurements are scalars and sensed with respect to the local coordinate system, the proposed angle-based formation control law is more robust against the misalignment of measurement coordinates. Simulation results are presented to illustrate the performance of the proposed control laws.

The need for better search and rescue capabilities has led to the increased demand for collaborative aerial-ground multi-robot deployments. However, most existing solutions require high communication bandwidth or bulky sensor equipment that is not suitable especially for aerial robots. To make the execution of these tasks more efficient, this paper proposes an angle-specified heterogeneous leader-follower formation framework consisting of unmanned aerial vehicles (UAVs) flying in a 3D space and ground robots moving in a 2D plane. The UAVs are controlled to maintain a desired angle-specified formation with the first three UAVs as the leaders forming a triangular shape and the remaining UAVs as the followers. The follower UAVs only need direction measurements to track the leader UAVs. For the ground robots, two leader robots track the UAV group and determine the orientation and scale of the ground formation, while the follower robots track the leader robots using only direction measurements. The proposed heterogeneous formation framework is energy-efficient as most robots only require low-cost and lightweight direction measurements. The stability of the proposed formation control algorithms is proved and validated through various physical application experiments.