Publications

This paper deals with the modeling and parameter tuning of a spar-type floating wind turbine with a tuned mass damper (TMD) installed in nacelle. Firstly, a mathematical model for the system surge-heave-pitch motion is established based on first principles. Secondly, different parameter tuning methods are adopted to find the optimal TMD parameters for load reduction. Thirdly, nonlinear wind turbine simulations with different designs are conducted under different wind and wave conditions. The results show that TMD with small spring and damping coefficients will help to produce much load reduction in above rated condition. However, it may deteriorate system performance when the turbine is working below rated. In contrast, the design with large spring and damping constants will achieve moderate load reduction in both working conditions.

Sales forecasting is an essential task in retailing. In particular, consumer-oriented markets such as fashion and electronics face uncertain demands, short life cycles and a lack of historical sales data which strengthen the challenges of producing accurate forecasts. This survey paper presents state-of-the-art methods in the sales forecasting research with a focus on fashion and new product forecasting. This study also reviews different strategies to the predictive value of user-generated content and search queries.

This paper investigated the problem of control design for a class of stochastic systems with Markovian jump parameters and time-varying delays. For the model under consideration, a passivity-based approach is introduced for designing mode-dependent output feedback controllers with mixed discrete and distributed delays. A Lypunov-Krasovskii function (LKF) is defined to establish new required sufficient conditions for ensuring exponentially mean-square stability and the passivity criteria, simultaneously. Moreover, controller gains are calculated based on a convex optimization method by solving a Linear Matrix Inequality (LMI). Finally, simulation results are provided to illustrate the effectiveness of our approach.

This paper investigates the problem of robust fault detection system design for a class of uncertain Takagi–Sugeno (T–S) models. The system under consideration is subject to unknown input and time-varying delay. The fault detection system is designed such that the unknown input is thoroughly decoupled from residual signals generated by the fault detection system. Furthermore, the residual signals show the maximum possible sensitivity to the faults and the minimum possible sensitivity to the external disturbances. The model matching approach is utilized to tackle the effects of parametric uncertainties in the model of the system. The design procedure is presented in terms of Linear Matrix Inequalities (LMIs). Some remarks are given to analyze the proposed method. Finally, a numerical example is presented to show the effectiveness of the proposed method.

In this paper, a novel strategy for structural vibration control of multi-structure systems is presented. This strategy pays particular attention to mitigating negative interstructure interactions. Moreover, it is based on recent advances in static output–feedback control, which make possible the efficient computation of decentralized velocity-feedback controllers by solving a single-step optimization problem with Linear Matrix Inequality constraints. To illustrate the main ideas, a local velocity-feedback energy-to-peak controller is designed for the seismic protection of a two-building system. This controller is remarkably effective and extremely simple. Moreover, it can also be implemented by a linear passive damper. To assess the effectiveness of the proposed controller, numerical simulations are conducted with positive results.

This article investigates the stability issue for a class of switched nonlinear systems whose control inputs include time delay and sampling. It is assumed that a stabilizing controller is predesigned for the nominal system such that it is stable under a certain switching signal. However, in the presence of input delay and sampling, the system may not be stable under the same stability criteria. Besides, the switching signals are discussed in two cases, that is, the switching signal of the system is transmitted to the controller in real time and only the sampled information of the switching signal is available to the controller at each sampling instant. For the latter, the asynchronous motions between the subsystems and the candidate controllers are caused and the closed‐loop system is rewritten as sampled switched nonlinear delay system with an augmented switching signal. By constructing sampling interval‐dependent Lyapunov–Krasovskii functional and using the theory of the asynchronous switched delay system, we establish the stability conditions on the switching signal which depends on the size of the delay, the upper bound of the sampling interval, and the dwell time. Finally, a numerical example is given to illustrate the effectiveness of the proposed results.

Numerous items, small order, and frequent delivery are the characteristics of many distribution centers. Such characteristics generally increase the operating costs of the distribution center. To remedy this problem, this study employs the Entry‐Item‐Quantity (EIQ) method to identify the characteristic of the cigarette distribution center and further analyzes the importance degree of customers and the frequently ordered products by means of EQ/EN/IQ‐B/IK statistic charts. Based on these analyses as well as the total replenishment cost optimization model, multipicking strategies and combined multitype picking equipment allocation is then formulated accordingly. With such design scheme, the cigarette picking costs of the distribution center are expected to reduce. Finally, the specific number of equipment is figured out in order to meet the capability demand of the case cigarette distribution center.

This paper investigates the problem of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msub><mml:mi>ℋ</mml:mi><mml:mi>∞</mml:mi></mml:msub></mml:mrow></mml:math>state-feedback control for a class of two-dimensional (2D) discrete-time Markovian jump linear time-delay systems with defective mode information. The mathematical model of the 2D system is established based on the well-known Fornasini-Marchesini local state-space model, and the defective mode information simultaneously consists of the exactly known, partially unknown, and uncertain transition probabilities. By carefully analyzing the features of the transition probability matrices, together with the convexification of uncertain domains, a new<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msub><mml:mi>ℋ</mml:mi><mml:mi>∞</mml:mi></mml:msub></mml:mrow></mml:math>performance analysis criterion for the underlying system is firstly derived, and then the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:msub><mml:mi>ℋ</mml:mi><mml:mi>∞</mml:mi></mml:msub></mml:mrow></mml:math>state-feedback controller synthesis is developed via a linearisation technique. It is shown that the controller gains can be constructed by solving a set of linear matrix inequalities. Finally, an illustrative example is provided to verify the effectiveness of the proposed design method.

This paper considers the sliding mode control problem for a kind of dynamic delay system. First by utilizing Lyapunov stability theory and a linear matrix inequality technique, an observer based on delayed output feedback is constructed. Then, an integral sliding surface is presented to realize the sliding mode control for the system with the more available stability condition. Finally, some numerical simulations are implemented to demonstrate the validity of the proposed control method.

A mixed H 2 / H ∞ output-feedback control design methodology for vibration reduction of base-isolated building structures modelled in the form of second-order linear systems is presented. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities. A controller that guarantees asymptotic stability and a mixed H 2 / H ∞ performance for the closed-loop system of the structure is developed, based on a Lyapunov function. The performance of the controller is evaluated by means of simulations in MATLAB/Simulink.

In decision making problems, experts need to assess a number of values in a side of reference domain higher than in the other one,that is, experts use unbalanced linguistic values to express their evaluation for problems. In this paper, we propose a new linguistic aggregation operator to deal with unbalanced linguistic values in group decision making. Based on 2-tuple representation model of linguistic values and linguistic hierarchies, we express unbalanced linguistic values. Moreover, we present the unbalanced linguistic ordered weighted geometric operator to aggregate unbalanced linguistic evaluation values. Some properties of the unbalanced linguistic ordered weighted geometric operator are also obtained. An illustration example shows the proposed approach seems more effective for linguistic group decision making problem.

Vehicle crash is a complex behavior to be investigated as a challenging topic in terms of dynamical modeling. On this aim, fuzzy logic can be utilized to analyze the crash dynamics rapidly and simply. In this paper, the experimental data of the frontal crash is recorded using an accelerometer located at the centre of the gravity of the vehicle. The acceleration signal was the raw data from which the collision intensity expressed by the kinetic energy and the jerk were derived. The fuzzy logic model was then developed from the two inputs namely kinetic energy and jerk. The output variable is the crash severity expressed as the dynamic crash. The result shows that the jerk contributes much to the crash than the kinetic energy of the vehicle.

Fairness in machine learning has become a global concern due to the predominance of ML in automated decision-making systems. In comparison to group fairness, individual fairness, which aspires that similar individuals should be treated similarly, has received limited attention due to some challenges. One major challenge is the availability of a proper metric to evaluate individual fairness, especially for probabilistic classifiers. In this study, we propose a framework PCIndFair to assess the individual fairness of probabilistic classifiers. Unlike current individual fairness measures, our framework considers probability distribution rather than the final classification outcome, which is suitable for capturing the dynamic of probabilistic classifiers, e.g., neural networks. We perform extensive experiments on four standard datasets and discuss the practical benefits of the framework. This study can be helpful for machine learning researchers and practitioners flexibly assess their models' individual fairness. The complete code of the framework is publicly available <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> .

For wind turbine load mitigation, this paper proposes an active structural control deign of a hybrid mass damper installed at the tower top of a spar-type floating wind turbine. System dynamic model is established based on first principles and the polynomial curve fitting approach, while different steady-state points are derived. Then, a gain scheduling H2/H ∞ state feedback controller is designed by solving linear matrix inequalities, which aims to reduce the loading. At last, nonlinear simulations are performed under different wind and wave conditions, and the results demonstrate that more load reduction could be achieved at the expense of more energy consumption in mass damper actuator.

In this article, the issue of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathscr {L}_{1}$ </tex-math></inline-formula> control design is addressed for a class of delayed stochastic jump systems subject to semi-Markov jump parameters. The stochastic jump systems in the presence of positivity constraints are described by positive semi-Markov jump systems (S-MJSs). By constructing new linear Lyapunov functional dependent double integral, some sojourn-time-dependent sufficient conditions are established to realize the corresponding stochastic stability with a prescribed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathscr {L}_{1}$ </tex-math></inline-formula> -gain performance index. Then, a switching controller via gain matrix decomposition is designed to achieve positivity and stochastic stabilization with a prescribed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathscr {L}_{1}$ </tex-math></inline-formula> -gain performance, which can be solved with the help of linear programming approach. Finally, the virus mutation treatment model verifies the effectiveness of the theoretical results.