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In this paper, the consensus tracking problem is studied for a group of nonlinear heterogeneous multiagent systems with asymmetric state constraints and input delays. Different from the existing works, both input delays and asymmetric state constraints are assumed to be nonuniform and time-varying. By introducing a nonlinear mapping to handle the problem caused by state constraints, not only the feasibility condition is removed, but also the restriction on the constraint boundary functions is relaxed. The time-varying input delays are compensated by developing an auxiliary system. Furthermore, by utilizing the dynamic surface control method, neural network technology and the designed finite-time observer, the distributed adaptive control scheme is developed, which can achieve the synchronization between the followers' output and the leader without the violation of full-state constraints. Finally, a numerical simulation is provided to verify the effectiveness of the proposed control protocol. [ABSTRACT FROM AUTHOR]

Highlights • Compared with the existing results in Chu et al. (2015), Meng et al. (2018), the system considered in this paper is more general. Firstly, the time delay investigated in this paper is time-varying. Secondly, different from deterministic systems, this paper considers a class of stochastic systems. • By using the backstepping design technique, an observer-based linear controller is constructed. In stability analysis, based on an appropriate Lyapunov-Krasoviskii functional, an allowable sampling period T is derived to guarantee that the considered stochastic system is globally asymptotically stable in the mean square sense. • The proposed sampled-data controller is linear and independent of the time delay, which is more suitable for practical applications. Abstract This paper studies the global sampled-data output feedback stabilization problem for a class of stochastic nonlinear systems. The considered system is in non-strict feedback form with unknown time-varying delay. A state observer is introduced to estimate the unmeasured states. With the help of the backstepping method, a linear sampled-data output feedback controller is constructed. By choosing an appropriate Lyapunov–Krasoviskii functional and an allowable sampling period, it is shown that the stochastic system can be globally asymptotically stabilized in the mean square sense under the developed control scheme. Finally, two examples are presented to verify the effectiveness of the designed control scheme. [ABSTRACT FROM AUTHOR]

Aiming at the attitude control of an asymmetric morphing-wing aircraft, a compound control system is proposed. Based on the dynamic model of the asymmetric morphing-wing aircraft, the morphing wing is regarded as a new active control mechanism and the condition of using the asymmetric morphing wing is determined. A control strategy for the allocation of the control commands is designed by the logic function. The disturbance caused by the morphing wing is estimated by the extended disturbance observer and the variable structure control method with global sliding mode is used to design the compound control system which restrains the violent changes in parameters and disturbance during the process of morphing. According to the simulation, compared to the fixed-wing aircraft, the effectiveness of the asymmetric morphing wing is assessed and the robustness of the controller is also evaluated by the pertubation of the parameters. [ABSTRACT FROM AUTHOR]

We calculate the next-to-leading order (NLO) QCD corrections to J/ψ associated with W+b production from top quark decay. Our results show that the decay width for process t→J/ψ+W++b+X at the leading order is significantly enhanced by the NLO QCD corrections. This process has the potential to be detected at the LHC. It provides an interesting signature that could be studied at the LHC, and if the J/ψ associated production with W+b from top quark decay is really detected, it will be useful for testing the nonrelativistic QCD factorization formalism. [ABSTRACT FROM AUTHOR]

In this paper, the fully distributed consensus for a class of multiple Euler-Lagrange systems is investigated, where the protocol is designed under the event-triggered control framework and the dynamics of Euler-Lagrange systems are heterogeneous. Since only local information interactions at triggered instants can be used and the Euler-Lagrange systems are of relatively complex dynamics, it is challenging to achieve asymptotic consensus without using any global information (such as the Laplacian matrix information). By skillfully integrating the adaptive control, distributed control and event-triggered control techniques, a novel protocol is proposed for the investigated multiple Euler-Lagrange systems. It is proven that the asymptotic consensus can be achieved by the developed protocol. By a numerical example, the effectiveness of the developed protocol is illustrated. [ABSTRACT FROM AUTHOR]

We propose a heralded quantum repeater protocol based on the general interface between the circularly polarized photon and the quantum dot embedded in a double-sided optical microcavity. Our effective time-bin encoding on photons results in the deterministic faithful entanglement distribution with one optical fiber for the transmission of each photon in our protocol, not two or more. Our efficient parity-check detector implemented with only one input-output process of a single photon as a result of cavity quantum electrodynamics makes the entanglement channel extension and entanglement purification in quantum repeater far more efficient than others, and it has the potential application in fault-tolerant quantum computation as well. Meanwhile, the deviation from a collective-noise channel leads to some phase-flip errors on the nonlocal electron spins shared by the parties and these errors can be depressed by our simplified entanglement purification process. Finally, we discuss the performance of our proposal, concluding that it is feasible with current technology. [ABSTRACT FROM AUTHOR]

This paper aims at proposing the sliding mode control method based on event-triggered scheme for networked control systems with periodic denial-of-service (DoS) attacks in the network environment. Firstly, considering the possible security problem in open communication networks, an event-triggered strategy ensuring the security of communication links under DoS attacks is designed, which can weaken the adverse impact of jamming signals in communication while providing benefits in improving resource utilization. Secondly, combined with the event-triggered control strategy, by aid of constructing the sliding surface function, the sliding mode dynamics is deduced, and the stability criterion with disturbance attenuation performance in H ∞ sense is established by an improved inequality technique. On this basis, an control law is designed, which ensures the reachability of the sliding mode surface. Finally, the effectiveness of the control strategy is proved by a numerical example and an example of an inverted pendulum on a cart. [ABSTRACT FROM AUTHOR]

This paper presents a novel coupling characterization based robust control scheme for hypersonic vehicles. First of all, the attitude equations of a hypersonic vehicle are denoted, and the error dynamic model of the hypersonic vehicle is obtained based on the backstepping technique. Then, a robust coupling-based control scheme is proposed combining with the disturbance observer, and the asymptotic convergence is guaranteed through the sliding mode compensation. Finally, the integral absolute error (IAE) performance index is introduced, and the better performance of the proposed method is proven theoretically. The proposed method not only guarantees the asymptotic stability and the strong robustness, but also improves the dynamic performance via considering the coupling characterization into the controller design. The aerodynamic parameters perturbation and actual actuator constraints are considered in the numerical simulations, and the results demonstrate the validity of the control method in this paper. [ABSTRACT FROM AUTHOR]

Based on drag acceleration profile, a predictor-corrector guidance law which can guide longitudinal motion and lateral motion synergistically is proposed in this paper. The drag acceleration profile is designed through interpolating between upper drag boundary and lower drag boundary, and then corrected to eliminate the range error. The altitude error is eliminated by adjusting attack angle. The lateral error is eliminated by regulating the reversal time of bank angle. Comparing with the traditional methods, the proposed one can correct the 3-dimensional motion of the vehicle. Using interpolated drag acceleration profile, the flight constraints can be easily dealt with. Moreover, in a correction cycle, the method in this paper only needs twice trajectory predictions, which is favorable for on-board calculation. The simulation results indicate that the proposed guidance law has a high precision and robustness. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of finite-time fault-tolerant consensus protocols for a class of uncertain multiple mechanical systems. On the basis of the recursive design method and finite-time control theory, distributed consensus protocols and adaptive laws are developed by using locally available information. Fuzzy logic systems are employed to approximate the unknown functions. It is proved that if the designed parameters and functions in the protocols and adaptive laws are suitably chosen, the position errors and the velocity errors between any two mechanical systems will converge to a small neighborhood of zero in finite time. Finally, an example is given to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Two typical flight modes of hypersonic glide vehicles, equilibrium glide and skip glide, are researched in the paper. Firstly longitudinal kinematic models for hypersonic glide vehicle are established. Relative functions between velocity, height and fight path angle are deduced, and the changing laws of dynamic pressure, total load factor and heating rate with velocity are analyzed in the equilibrium glide mode. In addition, analytical equations between state parameters are presented under the condition of constant lift-drag-ratios. Numerical simulation method is applied to explain the effect of the initial parameters on the skip glide trajectory. The study can help improve the understanding and provide guidance for missions like trajectory prediction, planning and guidance. [ABSTRACT FROM AUTHOR]

On-line trajectory plan methods are of no guarantee of real time for using optimization searching algorithms. They are unpractical to be adopted in engineering application for reusable launch vehicles (RLV) in terminal area energy management (TAEM). An prediction and acquisition straight line (PASL) phase is added before the heading alignment cone (HAC) to accomplish the TAEM trajectory on-line planning in advance, thus decreasing the requirement for the real time performance. The vehicle's initial states of the TAEM phase referred to as the terminal states of the PASL phase can be predicted by calculating the analytic solution of three-degree freedom motion equations with zero aerodynamic angle. Taking dynamic pressure, normal acceleration and bank angle as constraints, it is transformed into a non-linear planning problem to generate the TAEM trajectory. The objective function is to search for the optimal HAC position with a minimum heading error to enter the HAC. In addition, a pneumatic-angle directive (PD) feedback tracking law is designed, where the open-loop commands are available once the trajectory is obtained. Finally, an illustrative example is given to confirm the efficiency of the TAEM method based on trajectory prediction. [ABSTRACT FROM AUTHOR]

In this study, a novel M-estimation based sparse grid quadrature filter (MSGQF) is proposed to improve the robust performance of the nonlinear system. We present a systematic formulation of the sparse grid quadrature filter (SGQF), and extend it to the discrete-time nonlinear system with abnormal measurement values. The M-estimation method is introduced in the SGQF, which uses the Huber's cost function to update the measurement covariance. Convergence on the modified robust SGQF is established and proved. The sufficient conditions are shown to ensure stochastic stability of the MSGQF. A target tracking problem has been conducted to demonstrate the accuracy of the MSGQF. When measurement abnormal values appear, it outperforms the unscented Kalman filter (UKF), the cubature Kalman filter (CKF) and the SGQF. Theoretical analysis and simulation results prove that the MSGQF provides significant performance improvement in the robustness of the nonlinear system. [ABSTRACT FROM AUTHOR]

Abstract This paper addresses formation control problem with collision avoidance for general linear multi-agent systems via an optimal control strategy. In the proposed optimal control strategy, a novel potential function is designed to accomplish formation of multi-agent systems (MASs) with obstacle/collision avoidance capability, which can avoid rectangle obstacles accurately. In this potential function, a novel relative velocity based self-adaptive detection region is proposed to avoid collisions with adjacent agents. Moreover, a non-quadratic avoidance performance index is constructed based on inverse optimal control approach. Then, the optimal control strategy is designed to guarantee the asymptotic stability of the closed-loop system and optimality of the proposed performance index. Finally, a simulation example is given to illustrate the efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

• Previous prediction of the steady-oscillatory transition in published works has been summarized, and we find the transition point has yet to come to consensus. • The critical Reynolds number is predicted numerically by a present method SCM-ACM with high accuracy and fewer nodes. • The temporal evolution of velocity, the amplitude evolution, and the distribution of dimensionless angular frequency are studied. Massive computations of three-dimensional (3D) flow in subcritical flow state are carried out to investigate the transition from 3D steady flow to time-periodic oscillatory flow via Hopf bifurcation in a cube. Previous prediction of the steady-oscillatory transition in published works has been summarized. The transition point in lid-driven cavity has yet to come to consensus as the critical parameters are predicted in a wide range of values. The 3D unsteady governing equations are solved numerically using the spectral collocation method (SCM) in combination with the artificial compressibility method (ACM), SCM-ACM, a combined method with high accuracy that we developed. The temporal velocity evolution, amplitude evolution and dimensionless angular frequency are investigated. The accurate critical Reynolds number R e c r is predicted by Richardson extrapolation. Results show that the initial conditions have significant effect to obtain the velocity which gradually approaches to steady state in the subcritical flow state, and appropriate initial conditions are given to efficiently obtain stable results by gradually increasing R e. Exponential decay of velocity amplitude becomes weaker with the increase of R e , and the decay rate is strictly linear against R e , while the dimensionless angular frequency remains constant. The R e c r is affected by the number of nodes, which has also been observed by Feldman and Gelfgat [1] and Kuhlmann and Albensoeder [2] , while the critical frequency is unaffected by the number of nodes in the present results. It also indicates that the R e c r and the constant dimensionless angular frequency can be innovatively predicted with more accuracy and much fewer nodes. The improved point of steady-oscillatory transition in 3D lid-driven cube is R e c r = 1916.6 via Hopf bifurcation by Richardson extrapolation with dimensionless angular frequency ω = 0.5752. [ABSTRACT FROM AUTHOR]