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AZ31/7075 composite with the addition of Zn foil (about 100 μm in thickness) in the dissimilar material interface was successfully fabricated by pre-extrusion+caliber rolling composite process. The microstructure evolution especially for the composite interface was characterized by optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) and the microhardness test was also performed. The effect of the Zn intermediate layer on the product during the extrusion and caliber rolling was explored. The results show the hard 7075 Al alloy as the core can refine the grain size of AZ31 alloy. In addition, introducing Zn intermediate layer can reduce or completely avoid the formation of Mg-Al intermetallic compounds. The temperature increased by extrusion and deformation results in the remelting of eutectic Mg-Zn phase, and the diffusion of both elements from the solid to the liquid phase are accelerated. However, discontinuous cracks can be observed in the Mg-Zn diffusion layer but will be healed after caliber rolling. The MgZn2 intermetallic compound generated at Mg-Zn diffusion layer has high hardness (161HV), but the overall hardness of bonding layer is not changed a lot due to thinner thickness of the Mg-Zn diffusion layer after deformation.

Summary: This article investigates the fuzzy sliding mode tracking problem for discrete‐time nonlinear interconnected systems (ICSs) via a previewable information approach. First, an augmented system containing tracking errors and previewable reference and disturbance signals is established for discrete‐time nonlinear ICSs according to a previewable length. Second, novel sliding surfaces are given and some sufficient conditions of making the sliding motion asymptotically stable are derived in term of linear matrix inequalities (LMIs). Next, fuzzy sliding mode control (SMC) laws are designed so that the controlled system can reach the sliding surfaces and keep on them thereafter, and compared to not having previewable signals, these designed control laws can also enable system outputs to better track the reference signals asymptotically. Finally, a simulation example is given to demonstrate the effectiveness of the proposed control law. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of preview sliding mode control for a class of nonlinear uncertain discrete-time singular systems with time-delays. A difference operator approach is used to deal with the controlled system such that the derived augmented systems including preview information of reference signal can be constructed. A suitable surface is proposed in the sense of admissibility by the free-weighed matrix technique. Based on this, a sliding mode controller with preview information is constructed incorporating with the tracking error to ensure that the closed-loop control system reaches the designed sliding mode surface within finite time. To apply the proposed control scheme to the practical engineering systems, the sliding mode tracking controller with preview information is developed for a DC motor based on the proposed control approach. The comparative experiment results demonstrate that the preview information of reference signal can improve the tracking performance. [ABSTRACT FROM AUTHOR]

This article immerses in the event‐triggered containment control problem for a Lipschitz‐like nonlinear multi‐agent system with multiple active leaders. First, two event‐triggered mechanisms with internal dynamic variables are designed in both sensor‐observer (S‐O) and controller‐actuator (C‐A) channels to monitor data transmission and reduce communication burden. Second, an observer is constructed with the aid of the output information to estimate the states that cannot be acquired directly. Then, a control protocol considering time‐varying communications delays is proposed based on the observer. Third, the boundedness analysis of the containment error system is constructed by Lyapunov stability theory, the sufficient conditions are given in light of strict feasible LMIs. Finally, the validity of the proposed controller is verified by two simulations. [ABSTRACT FROM AUTHOR]