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This paper addresses the problem of almost disturbance decoupling (ADD) using sampled-data output feedback control for a class of continuous-time nonlinear systems. Under a lower-triangular linear growth condition, a sampled-data output feedback controller is constructed based on the output feedback domination approach, and a Gronwall-Bellman-like inequality is established in the presence of disturbances. Even though a sampled-data controller is employed for easy computer implementation, the proposed controller is still able to achieve ADD under the commonly used continuous-time requirement, that is, the disturbances' effect on the output is attenuated to an arbitrary degree of accuracy in the L2 gain sense. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In actual engineering, material properties, load effects, and other factors of mechanical structures change due to long‐term use. In order to understand the operation of a mechanical structure in real time, it is crucial to obtain the dynamic trajectory of its reliability. Considering the time variability of a mechanical structure over time, uncertain random variables are introduced to express the uncertainty of various parameters of structures, and the Wiener process is used to describe the strength degradation process of structures so as to solve the calculation problem of time‐varying reliability of mechanical structures. Based on the advanced first‐order and second moment method (AFOSM), the proposed linearized Nataf change is used to complete the transformation from related nonnormal variables to independent standard normal variables in order to simplify the calculation process of reliability solution and solve the reliability calculation problem of random parameters subjected to arbitrary distribution. The deduced random variable sensitivity factor indicates the degree of influence of different random variables on the reliability of the mechanical structure, providing a theoretical basis for the optimal design and maintenance of a mechanical structure. The proposed method is analyzed using the cantilever beam and compared with the nonlinear Nataf transform and verified by the Monte Carlo simulation results. The results show that the proposed method can effectively solve the reliability sensitivity problem of structural system strength degradation. [ABSTRACT FROM AUTHOR]

In this study, the authors consider the problem of frequency regulation via output feedback for a hydraulic turbine system under unknown load variations. First, to address the difficulties in estimating the unmeasurable states and the unknown load variation, they introduce a universal finite‐time observer (UFTO) which can estimate unmeasurable states, unknown parameters and disturbances under a unified framework. Based on the proposed UFTO, the unmeasurable wicket gate position, the flow rate and the load variation are estimated in a finite time for the hydraulic turbine system. Then by introducing a coordinate transformation, the state‐space model of hydraulic turbine system is converted into a simple form for which a state feedback control law is constructed using the adding a power integrator approach. Combining the UFTO with the finite‐time control law, an output feedback controller is designed to regulate the frequency of the hydraulic turbine system. Computer simulations are also given to validate the proposed finite‐time output feedback controller. [ABSTRACT FROM AUTHOR]