Observer‐based tracking control for switched stochastic systems based on a hybrid 2‐D model

This paper is concerned with the observer‐based output tracking problem for a class of linear switched stochastic systems with time delay and disturbance by using repetitive control approach. More precisely, a two‐dimensional hybrid model is incorporated to obtain and optimize the repetitive controller. In particular, the repetitive controller is used to improve the tracking performance through its continuous learning actions. In addition, an equivalent‐input‐disturbance estimator is incorporated into the repetitive control design approach to reduce the effect of the external disturbances. The main aim of the control design is to track the periodic reference signal with the measured output of the system under consideration even in the presence of an unknown bounded disturbance. By constructing a suitable Lyapunov‐Krasovskii functional and using average dwell time approach and Jensen inequality, sufficient conditions are obtained in terms of linear matrix inequalities to guarantee the mean‐square exponential stability of the considered system. Eventually, a numerical example is provided to demonstrate the effectiveness of the developed method.     

Analytical closed form model for static pull-in analysis in electrostatically actuated torsional micromirrors

The objective of this work is to create an analytical framework to study the static pull-in and also equilibrium behavior in electrostatically actuated torsional micromirrors. First the equation governing the static behavior of electrostatic torsion micromirrors is derived and normalized. Perturbation method, the method of straight forward expansion is utilized to find the pull-in angle of the mirror. Comparison of the presented results with numerical ones available in the literature shows that the proposed second order perturbation expansion gives very precise approximations for the pull-in angle of the mirror. Then straightforward perturbation expansion method is used again to analytically simulate the voltage dependent behavior in electrostatic torsion micromirrors. The results are compared with numerical and experimental findings and excellent agreement is observed.     

A new model to mitigating random disruption risks of facility and transportation in supply chain network design

In this article, we study the design problem of a reliable stochastic supply chain network in the presence of random disruptions in the location of distribution centers (DCs) and the transportation modes. It is assumed that a disrupted DC does not necessarily fail the whole of its capacity, and may lose a fraction of that, and rest of demand can be served by other DCs. We introduce a new strategy called soft-hardening strategy where the fraction of the lost capacity depends on the amount of investment for opening and operating. Additionally, the conditional value-at-risk (CVaR) approach is applied to control the risk of model. Finally, to solve the model, first we present an exact solution method by reformulating the problem as a second-order cone programming model, and second a hybrid algorithm combining tabu search and simulated annealing algorithms is developed.     

Shape identification problems on detecting of defects in a solid body using inverse heat conduction approach

In this paper, a new shape identification method in the inverse heat conduction problem (IHCP) is applied to detect the location and size of defects in a solid body. Different defects are modeled in a solid body as an elliptical geometry whose parameters are estimated with a proposed inverse algorithm. The inverse algorithm consists of direct, inverse analysis, and gradient-based optimization method. The direct analysis is used a finite-element method in an unstructured grid system to solve the direct heat conduction problem. The inverse analysis is based on recording temperatures data on surface of solid body that calculates the objective function. The employed gradient-based optimization method is constructed using the adjoint, sensitivity, and conjugate gradient method (Powell-Beal’s version) that are used to calculate the gradient of objective function, step size, and minimizing the objective function, respectively. The effects of different noisy temperature data, different cavities on some domains, and different type of defects such as poor cure, porosity, and crack are investigated in this work. The results show that this proposed inverse algorithm is more efficient in detection of defects.     

Chinese-Based Spearcons: Improving Pedestrian Navigation Performance in Eyes-Free Environment

This article presents nonspeech audio (i.e., English-based spearcons and Chinese-based spearcons) to represent distance, and forward-direction for pedestrian navigation in an eyes-free environment. Experiment in the field is carried out with the involvement of 10 participants (i.e., native Chinese) using within-subject design to evaluate English-based spearcons, Chinese-based spearcons, and Chinese text-to-speech (TTS). Results from the experiment suggest that Chinese-based spearcons are efficient in task completion compared to Chinese TTS. Moreover, Chinese-based spearcons are more effective in conveying distance and forward-direction compared to English-based spearcons in pedestrian navigation. Overall, participants have shown their satisfaction with Chinese-based spearcons as an auditory feedback in pedestrian navigation.