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An event-triggered control scheme is proposed for attitude tracking of Reusable Launch Vehicle (RLV) by combining adaptive and super-twisting techniques. Firstly, an adaptive event-triggered super-twisting control (AETSTC) strategy for multi-variable second-order nonlinear systems with unknown external disturbances is designed, which can adaptively adjust the control gains with respect to the unknown external disturbances and save computational cost or limited network resources while ensuring the desired control performance. Then, a formal proof of the stability of the closed-loop systems under the proposed method is derived based on Lyapunov stability theory, and the Zeno-free execution of triggering sequences is also guaranteed. Furthermore, the proposed AETSTC strategy is applied on attitude control of RLV without any knowledge of the bounds of external disturbances. Finally, simulation results on attitude tracking of RLV are provided to illustrate the efficiency and advantage of the developed algorithm.

The efficient conversion of aryl halides to phenols under mild reaction conditions remains a great challenge. Here we demonstrate that a facile and efficient hydroxylation reaction of aryl halides with water could be accomplished through a merger of a heterogeneous organic semiconductor graphitic carbon nitride (g-C3N4) photocatalyst and a homogeneous nickel(II) bipyridine organometallic catalyst under visible-light irradiation at room temperature. The protocol is tolerant to a wide range of substituted aryl halides, resulting in various phenol products with excellent conversion and selectivity. It is worth noting that the OH group of the resulting phenols originating from water increased the environmental friendliness of the reaction. It is worth noting that among all the previously reported catalysts (even including thermal catalysts with harsh reaction conditions), our Nidabpy/g-C3N4 dual catalytic system demonstrated the highest catalytic activity reported in the shortest reaction time. This remarkable catalytic performance was attributed to the strong interaction between the Nidabpy complex and g-C3N4, which decreased the transfer distance of photogenerated electrons transferring to Ni(II), accelerating the catalytic cycle. Furthermore, g-C3N4 was easily recovered from the reaction mixture and reused five times, showing the good potential of green hydroxylation reactions for large-scale industrial application.

Issues of controller design via small gain theorem for tethered satellite system (TSS) during orbit maneuvering under transversal thrust are considered. First, dynamic equations of tethered satellite system in orbital maneuvering are established based on a dumbbell model. It is proved that the in-plane system is weak minimum phase by selecting a proper Lyapunov candidate function, and there are some difficulties for controller designing based on nonlinear model directly. Next, a controller is designed by utilizing Small-gain Theorem based on a control oriented model. An input-to-state stable (ISS) based tether rate control law is derived as the reference signal for the tether length system. A tether tension control law is proposed such that the uncertainties caused by linearization will be suppressed by properly selected control parameters and the closed loop system will be forced to a small neighborhood of origin as time approaches infinity. Finally, numerical simulation results demonstrate the validity of the proposed algorithm.

This work focus on controller designing for tethered satellite system (TSS) during orbit maneuvering under transversal thrust. First, dynamic equations of tethered satellite system in orbital maneuvering are given based on dumbbell model. A linear model of the in-plane subsystem is derived for controller designing. Then, an input-to-state stable (ISS) control law for the in-plane angle system is obtained, which will be the reference signal for the tether length subsystem. Next, the tether tension control law based on small-gain theorem guarantees the stability of the closed-loop system and it is proved that states of the system will be forced to a small vicinity of the equilibrium point with properly selected control parameters. Finally, numerical simulation results demonstrate the validity of the proposed algorithm.

A command filtered back-stepping attitude controller is exploited and analyzed to design a dynamic state-feedback controller for a generic Reentry Vehicle. A novel back-stepping control that obviates the need to compute analytic derivatives in the traditional back-stepping design is presented by combining command filtered back-stepping method, sliding-mode-based integral filters and inputto-state stability (ISS) analysis. The ISS-modular approach provides a simple and effective way for controlling non-linear Reentry Vehicle satisfying the strict-feedback form, simultaneously solving the problem of “explosion of complexity” in traditional back-stepping approach. The stability analysis of the closed-loop system and the convergence of the aerodynamic angles are verified based on the smallgain theorem. Numerical simulations are included to demonstrate the effectiveness of the proposed control scheme.

The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle (FAHV). The model of interest includes flexibility effects and intricate couplings between the engine dynamics and flight dynamics. To overcome the analytical intractability of this model, a nominal control-oriented model is constructed for the purpose of feedback control design in the first place. Secondly, the multi-input multi-output (MIMO) quasi-continuous high-order sliding mode (HOSM) controller is proposed to track step changes in velocity and altitude, which is based on full state feedback. The simulation results are presented to verify the effectiveness of the proposed control strategy.

A nonlinear controller is exploited and analyzed for the nonlinear longitudinal dynamics of a generic Hypersonic Vehicle in this paper. The vehicle model is nonlinear, multivariable and unstable. A combined nonlinear observer and back-stepping technique is adopted for designing a dynamic output-feedback controller that provides stable tracking of the velocity and altitude reference trajectories. The stability analysis of the closed-loop system and the convergence of the system outputs are verified based on the small-gain theorem. Numerical simulation results from the nonlinear model illustrate the effectiveness of the proposed control scheme.

This paper discusses the application of a pulse vaccination strategy to prevent and control some infectious diseases, which is described by age-structured SIR model in which susceptible and recovered individuals are structured by chronological age, while infected individuals are structured by infection age (duration since infection). The time dependent disease-free equilibrium is determined, for which an explicit expression exists. The analytical results show that there exists a globally stable infection-free situation if the impulsive period T and proportion p satisfy R 0(p, T) < 1. Optimal problem is discussed: Pulse vaccination strategy with minimal costs at given R 0(p, T) < 1.

We formulate an age-structured SIS epidemic model with periodic parameters, which includes host population and vector population. The host population is described by two partial differential equations, and the vector population is described by a single ordinary differential equation. The existence problem for endemic periodic solutions is reduced to a fixed point problem of a nonlinear integral operator acting on locally integrable periodic functions. We obtain that if the spectral radius of the Fréchet derivative of the fixed point operator at zero is greater than one, there exists a unique endemic periodic solution, and we investigate the global attractiveness of disease-free steady state of the normalized system.

We study the application of a pulse vaccination strategy to eradicate the slowly progressing diseases that have infectiousness in latent period. We derive the condition in which eradication solution is a global attractor, this condition depends on pulse vaccination proportion p. We also obtain the condition of the global asymptotic stability of the solution. The condition shows that large enough pulse vaccination proportion and relatively small interpulse time lead to the eradication of the diseases. Moreover the results of the theoretical study might be instructive to the epidemiology of HIV.

In this paper, we study the application of a pulse vaccination strategy to eradicate hepatitis B and C modeled by SIV epidemic model. Since infection age is an important factor of hepatitis progression, we incorporate the infection age into the model. In this model, we consider the infectiousness of latent individuals. We derive the condition in which eradication solution is a global attractor, this condition depends on pulse vaccination proportion p and interpulse time T. We also obtain the condition of the global asymptotic stability of the solution. The condition shows that large enough pulse vaccination proportion and relatively small interpulse time lead to the eradication of hepatitis B and C. Moreover the results of the theoretical study might be instructive to the epidemiology of HIV.

In this paper, we develop a mathematical model for malaria with impulsive effect and infection-age, and consider the effect of blood transfusion and infected vector transmission. We derive the condition under which malaria goes to extinction.

Considering the impact of parametric uncertainties on Hypersonic Vehicle steady tracking control, a control approach based on integral sliding mode was proposed. First of all, linearized model of the Hypersonic Vehicle's longitudinal dynamics with uncertainties was obtained based on small disturbance linearization method with chosen trim point. Then, an integral sliding mode surface that guaranteed the global robustness of the control system was selected based on the uncertainties model. Next, sliding mode control law was designed and stability was analyzed based on the Lyapunov theory. At last, a simulation platform was built and results showed the effectiveness of the control approach through Monte-Carlo simulation.

This paper presents a novel 3-DOF PKM module that can be integrated into a manufacturing cell for large aircraft component machining. The design features of this module are briefly addressed. On the basis of the formulation of the overall Jacobian matrix, the design issues in this article are mainly focused upon the dimensional synthesis and stiffness evaluation with a goal to provide engineers with informative guidelines to conduct the detailed mechanical design, leading to a prototype machine being built by machine tool industry.

In this paper, we develop an HIV model that considers the dependence of HIV/AIDS progress on infection age (duration since infection), chronological age and impulsive antiretroviral treatment. The analytical results show that there exists a globally asymptotically stable infection-free state when the impulsive period T and drug-treatment proportion p satisfy R 0 ( p , T ) 1 . The numerical simulation results indicate that there exist T and p such that R 0 ( p , T ) 1 . Due to pulses, it would be difficult to obtain the optimal pulse interval in the age distribution of population. However, our results demonstrate the effect of the impulsive drug-treatment strategy on the dynamics of HIV/AIDS.

We develop an age-structured epidemic model for malaria with impulsive effect, and consider the effect of blood transfusion and infected-vector transmission. Transmission rates depend on age. We derive the condition in which eradication solution is locally asymptotically stable. The condition shows that large enough pulse reducing proportion and relatively small interpulse time lead to the eradication of the diseases.

We develop a mathematical model for the disease which can be transmitted via vector and through blood transfusion in host population. The host population is structured by the chronological age. We assume that the instantaneous death and infection rates depend on the age. Applying semigroup theory and so forth, we investigate the existence of equilibria. We also discuss local stability of steady states.