Unmanned Systems

Time-varying formation analysis and design problems for general linear multi-agent systems with switching interaction topologies and time-varying delays are studied. Firstly, a consensus-based formation control protocol is constructed using local information of the neighboring agents. An algorithm with three steps is presented to design the proposed formation control protocol. Then, based on linear matrix inequality technique and common Lyapunove–Krasovskii stability theory, sufficient conditions for general linear multi-agent systems with switching topologies and time-varying delays to achieve time-varying formation are given together with a time-varying formation feasibility condition. Finally, a numerical simulation is given to demonstrate the effectiveness of the obtained theoretical results.

This paper studies the distributed formation tracking control problem of heterogeneous multi-agent systems where the multiple targets have unknown inputs with finite dimensional Fourier decompositions and each target’s measurement output is just available to partial agents. A distributed observer-based formation tracking control algorithm is proposed. The distributed observers are based on the consensus protocol and designed to estimate the inputs and states of all targets from the available measurement outputs and neighbor information. The tracking controller is a state feedback based on the estimated state center of the targets. It is proved that the estimation errors of all agents converge to zero, if and only if each target node in the extended topology is reachable from each agent node and the consensus gain is larger than certain value. It is further proved that under the formation tracking control algorithm, the agents can asymptotically achieve predesigned formation and encircle the targets. A numerical simulation example is given to verify the validity of the algorithm.

This paper investigates the attitude synchronization and tracking problem for multiple spacecraft with an arbitrary differentiable reference. Considering the reference as a leader, the attitude synchronization and tracking problem is then transformed into a leader-following problem. Based on the quaternion representation of the attitude, the attitude tracking error dynamics and kinematics are derived. Treating the dynamics and kinematics as two cascaded subsystems, a back-stepping consensus protocol is designed, and its stability is analyzed using Lyapunov theorem. The proposed protocol is fully distributed since only the local and neighboring information are used. Finally, numerical simulations are performed to verify the effectiveness of the proposed protocol.

This paper presents novel affine formation algorithms and implementations in different scenarios for the coordination of multi-agent systems with triple-integrator agent dynamics for both sampled-data and continuous-time settings. The agents in affine maneuver control are to be capable of producing required geometric shapes and simultaneously accomplishing desired maneuvers such as shearing, rotation, translation and scaling. From existing work, these tasks can be accomplished for systems whose agent dynamics are described using double-integrators and the agents communicate continuously in time. In some practical situations, however, the inter-agent communication may be limited to periodic intervals of time. Furthermore, a wide range of systems is governed by complex dynamics described with higher-orders. This paper presents two novel algorithms based on triple-integrator agent dynamics. Four implementation cases comprising of two scenarios each studied in both continuous-time and sampled-data cases are considered. Under the proposed algorithms, the collection of agents are capable of tracking time-varying targets which are affine transforms of the reference formation, if the leaders have knowledge of the required formation maneuvers. Detailed implementation results are presented to demonstrate the efficacy of the proposed algorithms.

The formation control problem in multi-quadrotor systems is studied in this paper. Each quadrotor has limited access to its neighbors’ information due to communication constraint. First, the dynamics model of the quadrotor is linearized using Newton–Euler method. The distributed formation control law is then designed and the stability analysis is provided. An experimental platform is built with three Parrot Bebop drones and an indoor motion capture system. Numerical and experimental results are provided to show the effectiveness of the proposed algorithms.

This paper presents a critical analysis of some of the most promising approaches to geometric collision avoidance in multi-agent systems, namely, the velocity obstacle (VO), reciprocal velocity obstacle (RVO), hybrid-reciprocal velocity obstacle (HRVO) and optimal reciprocal collision avoidance (ORCA) approaches. Each approach is evaluated with respect to increasing agent populations and variable sensing assumptions. In implementing the localized avoidance problem, the author notes a problem of symmetry not considered in the literature. An intensive 1000-cycle Monte Carlo analysis is used to assess the performance of the selected algorithms in the presented conditions. The ORCA method is shown to yield the most scalable computation times and collision likelihood in the presented cases. The HRVO method is shown to be superior than the other methods in dealing with obstacle trajectory uncertainty for the purposes of collision avoidance. The respective features and limitations of each algorithm are discussed and presented through examples.