This paper proposes a distributed formation control approach for a team of vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) subject to switching topologies. The communication topology among UAVs is allowed to be with weak connectivity, in the sense of satisfying a uniformly jointly connected assumption. Since VTOL UAV systems are typically underactuated, a hierarchical framework is introduced such that a distributed control scheme can be established using neighboring positions and velocities. In particular, a distributed command force is developed to fulfill the formation objective, and an applied torque is synthesized for the attitude to track the command attitude. This command attitude is extracted from the command force by using a backstepping idea. In addition, an auxiliary system with appropriate parameters is introduced to preserve thrust saturation constraint, to guarantee nonsingular command attitude extraction and to avoid usage of neighboring acceleration information. With proper choices of Lyapunov functions, explicit selection criteria for the control parameters are formulated to ensure the asymptotic stability of the closed-loop system. Simulations and experiments are provided to validate the proposed theoretical results.

This paper studies the distributed time-varying convex optimization problem for a class of nonlinear multiagent systems. An auxiliary system is first designed to estimate the global optimal state and its high-order derivatives by means of a distributed algorithm. Relying on this auxiliary system, the solution of the distributed time-varying convex optimization problem is converted into that of a tracking problem for a class of nonlinear systems. A tracking control scheme is then proposed based on the back-stepping strategy. Simulations are provided to validate the theoretical results.

This article studies the bearing-based distributed formation control problem of a group of vertical take-off and landing unmanned aerial vehicles subject to unknown disturbances. Both cases of constant and time-varying velocity leaders are considered and two distributed formation control algorithms are developed based on a hierarchical framework. More precisely, two bearing-based distributed commanded forces are, respectively, proposed to achieve the target formation maneuver. Then, a unified adaptive hybrid attitude control law is designed such that the command attitude, which is extracted from the command force, can be tracked globally. In addition, three auxiliary systems are proposed to guarantee the boundedness of the thrust, to avoid the singular problem of command attitude extraction, to obviate the usage of the acceleration information, and compensate the adverse of the disturbance. Globally, the asymptotic stability of the closed-loop system is proved through Lyapunov stable theory. It is shown that the prescribed formation control objective is achieved. Finally, simulation results are provided to validate the performance of the proposed control algorithms.

This paper develops a novel immersion and invariance (I&I)-based adaptive controller for nonlinear under-actuated quadrotor systems subject to uncertain inertial parameters. The objective is to drive the quadrotor to accurately track a reference trajectory. The controller synthesis is based on a hierarchical framework. First, the solution to the trajectory tracking problem is transformed to stabilizing its corresponding error system asymptotically. Second, to avoid singularity in the command attitude extraction, a saturated backstepping control strategy with smooth hyperbolic tangent functions is developed to synthesize a command force in the position loop, where an I&I adaptive methodology is introduced to update the mass estimation. The I&I adaption guarantees the asymptotic convergence of the mass estimation to its actual value. Third, in the attitude loop, the projection algorithm is used to update the inertial tensor estimations, which enables the estimations to be maintained within a prescribed range. Then, a rotation matrix-based applied torque with an initial condition constraint is synthesized. It is proven that, with appropriate control parameters, the proposed controller guarantees the asymptotic stability of the error system and then the trajectory tracking of the quadrotor is achieved. Finally, numerical simulations are given to verify and highlight the performance of the proposed controller.

In this article, a class of distributed quadratic games is considered over an undirected graph. The issue on the communication topology restriction is introduced and the players’ dynamics are with nonlinear dynamics and unknown time-varying perturbation. A distributed Nash equilibrium seeking algorithm is proposed based on a high-gain observer method, and the convergence is analyzed by the Lyapunov stability theory. It is shown that each player estimates the rival players’ states, and the errors between the players’ states and the Nash equilibrium are ultimately bounded by a small bound. Moreover, the presented algorithm is free of chattering phenomena because it is designed using the hyperbolic tangent function instead of the signum function to dominant the perturbation. The effectiveness of the proposed algorithm is validated via a simulation of the oligopoly game in which five firms produce the same products in a duopoly market structure.

This article studies the leader-follower formation tracking problem of multiple quadrotors. In particular, the quadrotors are steered to track a reference trajectory while maintaining a desired configuration. The reference trajectory is partially available to a subset of quadrotors, and each quadrotor just interacts locally with its neighbors. A distributed control algorithm is proposed under a hierarchical framework. First, by introducing a distributed saturation control strategy, a command force is synthesized for the position to track the reference trajectory with a desired displacement. Second, a bounded applied force and a nonsingular command attitude are extracted from the synthesized command force based on a proper choice criterion of control parameters. Last but not the least, an applied torque is designed for the attitude to track the command one. In terms of Lyapunov theory, it is shown that the overall closed-loop error system is asymptotically stable. This indicates the accomplishment of the concerned leader-follower formation tracking control objective of multiple quadrotors. Finally, the effectiveness of the proposed distributed control algorithm is verified through both simulations and experiments.