In this article, we consider the distributed formation navigation problem of second-order multiagent systems subject to both velocity and input constraints. Both collision avoidance and connectivity maintenance of the network are considered in the controller design. A control barrier function method is employed to achieve multiple control objectives simultaneously while satisfying the velocity and input constraints. First, a nominal distributed leader-following formation controller is proposed which satisfies the velocity and input constraints uniformly and handles switching communication graphs. A nonsmooth analysis is employed to prove the global convergence of the controller. Then, a topology-based connectivity maintenance strategy using a new notion of the formation-guided minimum cost spanning tree is proposed and the corresponding barrier function-based constraints are derived. The barrier function-based collision-avoidance conditions are also developed. All barrier function-based constraints are then combined to formulate a quadratic programming problem which modifies the nominal controller when necessary to achieve both collision avoidance and connectivity maintenance. Simulation results demonstrate the effectiveness of the proposed control strategy.

In this paper, a new class of finite-time consensus controller is designed for second-order multi-agent systems subject to input saturation. Only a single saturation function is involved in the proposed controller which distinguishes it from previous ones. The proposed controllers achieve finite-time consensus using only relative state measurements. Both leaderless and leader-following consensus problems are studied. Comparisons of the proposed controllers with other existing controllers are shown through simulation examples.

This paper is devoted to tackling the robust collision avoidance formation navigation problem for a class of multiple unmanned surface vehicles ( multi-USVs), where the USVs are modeled as underactuated nonlinear systems subject to state and input constraints. Furthermore, unknown external disturbances are taken into consideration, as they stem from diverse uncertainties associated with environmental loadings and are encountered in various practical situations. Considering the inherent nonlinear dynamics and the state and input constraints, a new kind of distributed model predictive control (MPC) based controllers is developed to achieve collision free formation navigation. Specifically, in light of the unavailability of accurate USV dynamics caused by unknown external disturbances, time-delay observers are constructed to estimate these disturbances. This estimation process facilitates the creation of a reliable predictive model, which in turn enables the design of an effective MPC controller. Subsequently, a class of distributed collision avoidance MPC formation navigation control strategies is presented and utilized such that the control inputs of USVs can be determined synchronously. It is shown that the time-delay observers can effectively estimate the external disturbances and lead to satisfactory performance of the distribute MPC based controller. At last, numerical experiments are conducted to validate the effectiveness of the present control strategy and to demonstrate its advantages over existing approaches.

Applying reinforcement learning (RL) algorithms to control systems design remains a challenging task due to the potential unsafe exploration and the low sample efficiency. In this paper, we propose a novel safe model-based RL algorithm to solve the collision-free model-reference trajectory tracking problem of uncertain autonomous vehicles (AVs). Firstly, a new type of robust control barrier function (CBF) condition for collision-avoidance is derived for the uncertain AVs by incorporating the estimation of the system uncertainty with Gaussian process (GP) regression. Then, a robust CBF-based RL control structure is proposed, where the nominal control input is composed of the RL policy and a model-based reference control policy. The actual control input obtained from the quadratic programming problem can satisfy the constraints of collision-avoidance, input saturation and velocity boundedness simultaneously with a relatively high probability. Finally, within this control structure, a Dyna-style safe model-based RL algorithm is proposed, where the safe exploration is achieved through executing the robust CBF-based actions and the sample efficiency is improved by leveraging the GP models. The superior learning performance of the proposed RL control structure is demonstrated through simulation experiments.

In this paper, the finite-time consensus problem for second-order nonlinear multi-agent systems under communication constraints is investigated, where each agent has a limited sensing range. A distributed discontinuous control protocol is proposed to make a team of agents reach consensus in finite time when there exist disturbances in multi-agent systems. Then, for multi-agent systems without disturbances, a new piece-wise continuous protocol is presented to make agents achieve consensus in finite time. Furthermore, it is shown that initial interaction patterns are preserved under these control protocols. Finally, some numerical examples are provided to illustrate the theoretical results.

This paper considers consensus control of second- order multi-agent systems subject to both velocity and input constraints under general directed communication graphs. A new class of distributed consensus controller is proposed which is shown that under proper initial velocity conditions, consensus can be achieved while both the velocity and input constraints are satisfied during the consensus process. The proposed controller can be designed without relying on global information about the communication graph such as the eigenvalues of the Laplacian matrix. Extensions to dynamic formation control and leader- following consensus with both velocity and input constraints are also presented based on the consensus controller. Furthermore, sampled-data leader-following case is also investigated when communication rate is constrained. Simulations on the outer-loop coordination control of multiple quadrotors are used to illustrate the effectiveness of the proposed controllers.