In this paper, the finite-time fault-tolerant containment control for multiple unmanned aerial vehicle (UAV) systems is proposed. Unlike most existing studies that mainly address input magnitude saturation while neglecting rate constraints, a first-order dynamic system is incorporated to generate control inputs subject to both magnitude and rate saturation. Furthermore, a novel auxiliary system and a controller-coupled neural network observer are developed to compensate for the insufficient input signal and estimate the unknown dynamics caused by faults, respectively. Finally, by integrating the observer and auxiliary system, a fault-tolerant finite-time containment controller is constructed, and the effectiveness is validated through hardware-in-the-loop simulations.

In this paper, a formation controller for propeller-driven car-like robots is developed, which is subject to input amplitude, rate saturation, and the jointly connected topology. First, the model of the propeller-driven car-like robot is established, where actuator dynamics, amplitude, and rate saturation are considered. Second, the Gauss integration function is used to approximate the input saturation. Rate saturation will be converted into command input saturation and will be achieved by an auxiliary system. Third, the formation controller is developed based on the backstepping control method, where the adaptive robust controller and neural networks are combined to deal with unmodeled dynamics and external disturbances. According to the Lyapunov stability theory, it is proved that the propeller-driven multirobot system will be stable under the developed controller, while signals in the closed-loop system are ultimately uniformly bounded. Finally, simulation and experiment results verify the effectiveness of the proposed formation control scheme.

In this paper, a formation controller for propeller-driven car-like robots is developed, which is subject to input amplitude, rate saturation, and steering fault-tolerant control. First, the model of the propeller-driven car-like robot is established, where actuator dynamics, amplitude, and rate saturation are considered. Second, the Gauss integration function is used to approximate the input saturation. Rate saturation will be converted into command input saturation and will be achieved by an auxiliary system. Third, the formation controller is developed based on the backstepping control and fault-tolerant control, where the adaptive robust controller and neural-network observer are combined to deal with steering fault. According to the Lyapunov stability theory, it is proved that the propeller-driven car-like robot formation will be stable under the developed controller, while signals in the closed-loop system are ultimately uniformly bounded. Finally, simulation and experiment results verify the effectiveness of the proposed formation control scheme.

A disturbance observer-based distributed practical prescribed-time formation tracking control strategy is proposed to address the tracking control problem of the formation of small tandem-rotor unmanned aerial vehicles (STR-UAVs) with external disturbances and model uncertainties, while accounting for actuator dynamics. First, a practical prescribed-time disturbance observer (PPTDO) is developed to estimate external disturbances and model uncertainties. Second, a prescribed-time sliding mode surface (PTSMS) is applied to achieve prescribed-time stability for the formation position and velocity loops. Third, a novel practical prescribed-time sliding mode filter (PPTSMF) is designed to eliminate the analytical calculation of the derivative of the force reference input in the actuator loop and avoid high-order differentiation. Finally, a practical prescribed-time formation tracking control strategy is proposed based on PPTDO, PTSMS, and PPTSMF, and its stability is rigorously proved. Moreover, simulations validate the effectiveness and superiority of the proposed formation control strategy under external disturbances and model uncertainties, while also accounting for actuator dynamics.

This paper proposes a task allocation algorithm based on the combination of reinforcement learning and deep neural networks to address the problem of multi-UAV cooperative multi-objective task allocation. It utilizes graph neural networks (GNN) and attention mechanisms to model the policy function, thereby constructing a task allocation strategy based on the collective state of the UAV swarm which enables the reinforcement learning algorithm to generalize to varying numbers of enemy target nodes in the environment. To improve the efficiency and stability of training, the S-sample batch reinforcement learning algorithm is adopted. The simulation results demonstrate that the algorithm can effectively solve the multi-UAV task allocation problem.

A cooperative trajectory planning algorithm of Multiple unmanned aerial vehicles (UAVs) based on Multi-Agent Proximal Policy Optimization (MAPPO) has been proposed for the three-dimensional cooperative trajectory planning. Firstly, considering the constraints of cooperative trajectory planning and the battlefield environment, a three-dimensional cooperative trajectory planning model is established. Secondly, based on the established trajectory planning model, the state space, action space, and reward function are designed to implement cooperative trajectory planning. Finally, simulation is carried out to verify that the planned trajectory satisfies the environmental and spatial cooperative constraints and is flyable.

The leader-follower consensus via event triggered control of first-order multiagent systems is proposed under jointly connected topology. Firstly, a state predictor is designed to obtain the rate of change of state information of neighboring nodes when the position information is known. Next, an event-triggered consensus control law containing neighbor node location information and state prediction information is established. Then a state-dependent event triggering condition is given for each agent, and control input will be update only if the event triggering condition is unsatisfied. Finally, it is proved that the proposed event-triggered consensus control algorithm can achieve leading-following consensus under jointly connected topology and exclude Zeno phenomenon using Lyapunov stability theory and algebraic graph theory. Furthermore, simulation is carried out to verify the proposed method is verified in Simulink.

The ISMC+IPLL (Improved Sliding Mode Control method with Improved Phase-Locked Loop) is proposed to reduce the jitter phenomenon of sensorless control for a permanent magnet synchronous motor (PMSM). Through influence analysis for the structure parameters of SMO to PMSM performance, the basis for determining the switching function and forming coefficient of ISMC+IPLL is constructed. Compared with traditional PI control and anti-integral saturation ASR control, the observation behavior of the ISMC+IPLL under step load and step speed is optimized to varying degrees, which effectively weakens the inherent jitter phenomenon of sensorless control for PMSM and provides a theoretical basis for establishing a high-performance control strategy for PMSM in the whole operation stage.

In this paper, an adaptive tracking controller for the propeller-driven wall-climbing robot is developed, which is subject to velocity-related input saturation and velocity constraint. First, the model of the propeller-driven wall-climbing robot is established, where actuator dynamics and input saturation are considered with velocity constraints. The strategy of active gravity balance is put forward, which simplifies the modeling but leads to the problem of velocity-related input saturation. Second, the Gauss integration function is used to approximate the velocity-related input saturation. The velocity constraint would be handled by employing the barrier Lyapunov-based transformation rather than the barrier Lyapunov function (BLF) method. Thirdly, the tracking controller is developed based on the dynamic surface control method, where the adaptive robust controller and neural networks are combined to deal with unmodeled dynamics and external disturbances. According to the Lyapunov stability theory, it is proved that the propeller-driven robot system will be stable under the developed controller, while signals in the closed-loop system are ultimately uniformly bounded. Finally, simulation results show the effectiveness of the proposed tracking control scheme.

A novel practical predefined-time sliding mode control strategy is proposed for the flight formation of a small tandem-rotor wheeled UAV (TRW-UAV) with unknown upper bound external disturbances and uncertainties in this paper. Firstly, a new predefined-time sliding mode surface is proposed to guide all errors of the position and velocity loops to converge to the origin in a predefined-time. Furthermore, a dynamic surface control approach is utilized to circumvent the higher-order differentiation when controlling the actuator loop. Secondly, a predefined-time adaptive law is designed for estimating external disturbances and uncertainties during the controller design process to construct a distributed practical predefined-time formation cooperative control strategy. Thirdly, a novel practical predefined-time criterion is utilized to rigorously demonstrate the stability of the proposed control strategy. Finally, the simulation results indicate that the proposed control strategy can deliver the practical predefined-time control when there are external disturbances and model uncertainties, and with higher convergence accuracies compared to some of the existing methods.

In this thesis, the guidance problem of missile is studied in the consideration of the factors of external disturbance, fall angle constraint and field angle constraint. Firstly, the fuzzy sliding mode guidance strategy is designed for the two-dimensional guidance model considering external disturbance and fall angle constraint. Secondly, the field angle threshold correction instruction with correction coefficient is applied based on the guidance law of fall angle constraint. Finally, the guidance strategy with fall angle and field angle constraint is proposed by the thinking of switching logic, the stability and convergence of the system state are given based on Lyapunov stability theory, and the effectiveness of the designed guidance scheme is verified by digital simulation.

Spinning electrodynamic tether systems (SEDTs) have promising potential for the active removal of space debris, the construction of observation platforms, and the formation of artificial gravity. However, owing to the survivability problem of long tethers, designing collision-avoidance strategies for SEDTs with space debris is an urgent issue. This study focuses on the design of collision-avoidance strategies for SEDTs with an electrodynamic force (Ampere force). The relative distance between the debris and the SEDT is first derived, and then two collision-avoidance strategies are proposed according to the two different cases. When debris collides closer to a lighter subsatellite, a stationary avoidance strategy is proposed to change the spatial position of the subsatellite by adjusting only the angular motion of the tether, which maintains the original orbit of the SEDT. When debris collides closer to a heavier main spacecraft, a comprehensive avoidance strategy is proposed to change the spatial position of the SEDT by slightly modifying the orbital height and changing the tether angular motion simultaneously. The numerical results illustrate that the proposed strategies promptly avoid potential collisions of an SEDT with space debris without significant changes in the orbital parameters of the SEDT.

This paper provides an event-triggered finite-time adaptive bounded controller for attitude tracking of spacecraft formation flying under external disturbances and limited communication. To facilitate the realization of bounded control, a novel full-order terminal sliding mode surface is established according to the hyperbolic tangent function. To reduce the communication frequency among formation members, an event-triggered control strategy that can converge to zero in finite time is investigated based on the full-order sliding mode surface. Under the proposed control strategy, the spacecraft only send their information to neighboring spacecraft when the trigger error exceeds the defined threshold. Rigorous theoretical analysis provides that finite-time convergence and Zeno-free are achieved under the proposed controller. Finally, numerical simulations are exhibited to illustrate the effectiveness of the proposed control law.

This article mainly studies the spin-up control of a spinning electrodynamic tether formation (SEDTF) consisting of three linearly distributed nanosatellites connected by two tethers. The main challenge of the spin-up process is that due to the coupling effect of two tethers, more significant tether deformation and attitude disturbance on tethered nanosatellites emerge than that of a single-tether system. To deal with this problem, the dynamic model is first established for analyzing flexible tether motions and attitude motions of three nanosatellites. A sliding mode control strategy is then proposed for the spin-up process. First, considering the underactuation problem of the tether system, a sliding mode controller with an adaptive law is proposed to track spinning motion and stabilize tether deformation by adjusting only the electrical current. Second, considering the disturbance of constantly oscillating tension force, a sliding mode controller with a fixed-time prescribed performance is proposed to ensure a fast stabilization of attitude motions. Numerical results validate a synchronized spin-up of an SEDTF. Under the regulation of the proposed control strategy, tether deformations are reduced to an insignificant level, and attitude motions of nanosatellites are stabilized around designated orientations.

This paper investigates the problem of cooperative guidance strategies for multiple missiles attacking a maneuvering target. Based on the consistency theory and algebraic graph, a fixed-time cooperative guidance law with a terminal line-of-sight (LOS) angle constraint is proposed. Initially, the maneuvers of target in the LOS direction and normal to the LOS are considered as disturbances affecting the missiles. A two-dimensional guidance encompassing three degrees of freedom model is formulated based on the missile-target kinematics. Next, the guidance law design is divided into two parts. Along the LOS, a disturbance observer estimates the disturbances, and a fixed-time convergent, time-coordinated guidance law is formulated, integrating a consensus protocol to handle these disturbances. In the LOS normal direction, an adaptive estimation method is utilized to estimate the upper bound of disturbance. A non-singular fast terminal sliding mode control method is employed to generate LOS normal acceleration commands while ensuring convergence to the sliding surface within a fixed time. Lastly, a scenario with three missiles engaging a maneuvering target is designed, and saturation limits are applied on the acceleration commands in both directions. The simulations validate the proposed cooperative guidance law’s accuracy and efficacy for multiple missiles with a LOS angle constraint.

This paper investigates a distributed adaptive finite-time containment control scheme for multiple unmanned aerial vehicles subject to external disturbances and input saturation. Combined with a novel indicator of the saturation degree designed by the hyperbolic tangent function, an adaptive method is proposed to deal with the input saturation issue, which considers both symmetry and asymmetry saturation. Moreover, to address the problem of the "explosion of terms" inherent in the traditional backstepping controller design, a fixed-time sliding mode differentiator is utilized to approximate the derivative of the virtual signal in the command-filtered backstepping method. Finally, the convergence of the errors and the practicability of the control law are verified by Lyapunov stability analysis and numerical simulations.

This paper investigates a finite-time coordinated controller for spacecraft formation flying subject to external disturbances and limited communication resources. An event-triggered strategy is adopted to reduce the communication between disturbance observer and controller, between controller and actuator, and between neighboring spacecraft, simultaneously, which is more significant for coordinated control. To compensate for the external disturbances, a hyperbolic tangent function-based adaptive finite-time disturbance observer is established without the advanced knowledge of the upper bound of the derivative of the disturbance. The designed disturbance observer and controller are integrated through event-triggered strategy. The stabilities of the closed-loop system can be verified by the Lyapunov theorem without applying the separation principle. Simulation studies are provided to prove the effectiveness of the proposed control scheme.

This article devotes to addressing the distributed adaptive finite-time containment control for the multi-UAVs with actuator saturation, faults, and external disturbances. A hyperbolic tangent function is presented to smooth the symmetric and asymmetric saturation functions. Then, the containment control for UAVs with actuator saturation and faults can be turned into a variable gain control problem. To address this problem, a Nussbaum function is specially designed in this article to solve the variable gain issue with the known control direction. Besides, the bounds of disturbances are estimated and compensated by adaptive laws. With the presented containment control laws, the follower UAVs will converge into the convex hull spanned by the leaders in a finite time. Finally, the convergence of the errors and the practicability of the control law are verified by Lyapunov stability analysis and numerical simulations.

Hydrogen, as a clean and pollution-free energy with high calorific value, is one of the best alternatives to fossil fuels. Hydrogen evolution reaction (HER), as a half reaction of electrochemical water splitting, has also received extensive attention. At present, the development of low-cost and high-performance hydrogen evolution catalysts still faces enormous challenges. In this work, we synthesized a series of RuNi/TiO2-oxMWCNT catalysts with different Ru and Ni ratio. After optimizing the composition and proportion, RuNi/TiO2-oxMWCNT with Ru: Ni=4:6 has the optimal hydrogen evolution performance. High HER performance of extremely low 14.8 mV overpotential at 10 mA.cm(-2) and 38.4 mV.dec(-1) Tafel slope with perfect stability is achieved, which is superior to most reported ruthenium-based catalysts and even commercial Pt/C. XPS and UPS indicates that there is a metal synergistic effect of Ru and Ni and a strong SMSI between Ru and TiO2 in the RuNi/TiO2-oxMWCNT catalyst, which helps to improve hydrogen evolution performance. This study provides a pathway for the rational design of multi-component nanostructured catalysts for HER.