In this article, a dynamic high-gain-based decentralized optimal fault-tolerant control (FTC) strategy for a class of strong interconnected systems with unknown actuator faults is proposed. The interactions considered are bounded by some functions that depend on all subsystems' states. A two-layer control framework is presented for each subsystem to steer its tracking error asymptotically to zero. In the upper layer, an error optimizer is designed to generate optimal error trajectory based on a local objective function that converges to zero. In the lower layer, with the aid of an auxiliary system, a trajectory-tracking fault-tolerant controller is given to adaptively accommodate the effects of parameteric uncertainties and actuator faults, where an adaptive high-gain approach is adopted to address the unknown strong interactions. In comparison with existing results, the proposed algorithm relaxes the requirement of output trajectory derivatives, and asymptotic tracking is accomplished. Application results obtained using an electrical power system case demonstrate the validity of the proposed algorithm.

Most of the recent research on distributed formation control of unmanned aerial vehicle (UAV) swarms is founded on position, distance, and displacement-based approaches; however, a very promising approach, i.e., bearing-based formation control, is still in its infancy and needs extensive research effort. In formation control problems of UAVs, Euler angles are mostly used for orientation calculation, but Euler angles are susceptible to singularities, limiting their use in practical applications. This paper proposed an effective method for time-varying velocity and orientation leader agents for distributed bearing-based formation control of quadcopter UAVs in three-dimensional space. It combines bearing-based formation control and quaternion-based attitude control using undirected graph topology between agents without the knowledge of global position and orientation. The performance validation of the control scheme was done with numerical simulations, which depicted that UAV formation achieved the desired geometric pattern, translation, scaling, and rotation in 3D space dynamically.

A novel tailless X-type flapping-wing micro air vehicle with two pairs of independent drive wings is designed and fabricated in this paper. Due to the complexity and unsteady of the flapping wing mechanism, the geometric and kinematic parameters of flapping wings significantly influence the aerodynamic characteristics of the bio-inspired flying robot. The wings of the vehicle are vector-controlled independently on both sides, enhancing the maneuverability and robustness of the system. Unique flight control strategy enables the aircraft to have multiple flight modes such as fast forward flight, sharp turn and hovering. The aerodynamics of the prototype is analyzed via the lattice Boltzmann method of computational fluid dynamics. The chordwise flexible deformation of the wing is implemented via designing a segmented rigid model. The clap-and-peel mechanism to improve the aerodynamic lift is revealed, and two air jets in one cycle are shown. Moreover, the dynamics experiment for the novel vehicle is implemented to investigate the kinematic parameters that affect the generation of thrust and maneuver moment via a 6-axis load cell. Optimized parameters of the flapping wing motion and structure are obtained to improve flight dynamics. Finally, the prototype realizes controllable take-off and flight from the ground.

This paper proposes a monitoring-based adaptive fault-tolerant control (FTC) scheme for a class of uncertain nonlinear systems with a backup actuator. Different from the existing switching-based FTC schemes, an actual issue of gradual actuator deactivation is first taken into consideration, i.e., faulty actuator cannot be deactivated immediately. To reconfigure the controller, a method of estimating the upper bound of the nonlinearity caused by the gradual deactivation is used, and modified shifting functions are introduced to improve the system transient performance. Once an actuator failure is detected by the integrated monitoring function, the reconfigured controller together with the backup actuator can ensure that the tracking error is limited to the prescribed performance within a preset time. Simulation on an aircraft system and experiment on a motor-driven disc have been demonstrated.