1,256 publications from this institution
In this article, we present a methodology that leads to seismic vibration suppression of a class of base isolated civil structures by means of magnetorheological dampers. Magnetorheological dampers are versatile devices that generate damping force by controlling the rheological properties of the constituting magnetorheological fluid through a varying magnetic field. Magnetorheological dampers are more efficient than other devices in terms of energy requirements, damping force and mechanical design. However, they exhibit a complex behaviour, characterised by the hysteretic response to a velocity input, which is rather difficult to model. This in turn makes imperative the use of non-linear control techniques to achieve the final objective. In this article, Bouc?Wen model is used to describe the dynamics of an magnetorheological damper and adaptive backstepping controller is developed to explore its performance in seismic vibration suppression.
The emerging big data allows educational studies to examine teaching and learning behaviors over time and at scale. Less available is population-representative big data. This paper builds the first nationally representative sample of teachers' online curation on a social media platform (i.e. Pinterest), the Public Instructional Network of School Resources (PINSR). This effort includes developing a big-rich data sampling framework, integrating social media data with administrative and census "ground truth" sources, and validating the population representativeness. Finally, we employ PINSR and present a worked example of teachers' social media curation behavioral patterns across regions and time.
This article deals with the dynamic sliding mode control (SMC) problem for unmatched nonlinear parameter‐varying systems. The unmatched nonlinear model refers to the systems matrices of control input and nonlinearity terms having inconsistent values and structures. A linear sliding surface function is constructed, and the resulting sliding mode dynamics is formulated into a full‐order descriptor nonlinear parameter‐varying system. Then, based on a parameter‐dependent Lyapunov function, the synthesis procedure of the sliding manifold is derived, which guarantees the asymptotic stability of the sliding motion. Furthermore, a dynamic SMC law is proposed to enforce the resultant closed‐loop system towards the sliding manifold in finite time. It is noteworthy that both the sliding surface and control law are depended on both time‐varying and measurable parameters. Finally, simulation studies are provided to unfold the validity of the proposed method.
Alternative material flow strategies in logistics networks have crucial influences on the overall performance of the networks. Material flows can follow push, pull, or hybrid systems. To get the advantages of both push and pull flows in networks, the decoupling-point strategy is used as coordination mean. At this point, material pull has to get optimized concerning customer orders against pushed replenishment-rates. To compensate the ambiguity and uncertainty of both dynamic flows, fuzzy set theory can practically be applied. This paper has conceptual and mathematical parts to explain the performance of the push-pull flow strategy in a supply network and to give a novel solution for optimizing the pull side employing Conwip system. Alternative numbers of pallets and their lot-sizes circulating in the assembly system are getting optimized in accordance with a multi-objective problem; employing a hybrid approach out of meta-heuristics (genetic algorithm and simulated annealing) and fuzzy system. Two main fuzzy sets as triangular and trapezoidal are applied in this technique for estimating ill-defined waiting times. The configured technique leads to smoother flows between push and pull sides in complex networks. A discrete-event simulation model is developed to analyze this thesis in an exemplary logistics network with dynamics.
The normal electromagnetic force distribution in stator system of axial flux permanent magnet synchronous motor (PMSM) has been thoroughly analyzed in this paper. The main composition of force wave causing vibration and noise has been proposed, and at the same time a calculation method of stator natural frequency of axial flux PMSM has been raised. Through this method electromagnetic force wave, natural frequency, vibration response, and electromagnetic noise of a 15 kW axial flux PMSM with 22 poles and 24 slots have been calculated; calculations and measured values are consistent by comparison. The noise sources of axial flux PMSM have been found in this paper, which provides the theoretical support for the suppression of electromagnetic noise of axial flux PMSM.
A composite anti-disturbance control problem for a class of nonlinear systems is studied in this paper. There are two types of disturbances in the systems, one is the matched disturbance with bounded variation rate, the other is the unmatched time-varying disturbances. A nonlinear disturbance observer is designed to estimate the matched disturbances, which can be presented separately from the controller design. By integrating DOBC with back-stepping method, a composite DOBC and back-stepping controller is proposed, and the disturbance estimations are introduced into the design of virtual control laws to compensate the unmatched disturbances. In addition, it is proved that all the states in the closed-loop system are uniformly ultimate bounded (UUB). Finally, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method.
The last few decades have witnessed the rapid growth of research & development on large-scale systems (LSSs) due to the increasing complexity and the growing demand of modern engineering systems. The LSSs can normally be viewed as interconnections of multiple subsystems. Many practical systems can be described by the LSSs such as power systems, multi-robot systems, communication networks, transportation networks, and supply chains. In such large-scale systems, the centralized control framework may become impossible for its implementation. The decentralized and distributed controls have emerged as the attractive control methodologies to handle the scale and interactions of large-scale complex systems. However, the interactions among different subsystems introduce many challenges in the analysis and synthesis of such systems. Therefore, it is of significance to address several fundamental problems regarding real-time analysis, estimation and control of these systems.
This short paper addresses the problem of designing a QFT (Quantitative Feedback Theory) based controllers for the vibration reduction in a 6-story building structure equipped with shear-mode magnetorheological dampers. A new methodology is proposed for characterizing the nonlinear hysteretic behavior of the MR damper through the uncertainty template in the Nichols chart. The design procedure for QFT control design is briefly presented.
No abstract is provided for this article.
No abstract is provided for this article.
A main concern in applications of game theory is how to effectively select a Nash equilibrium, especially a pure-strategy Nash equilibrium for a finite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math>-person game in normal form. This selection process often requires the computation of all Nash equilibria. It is well known that determining whether a finite game has a pure-strategy Nash equilibrium is an NP-hard problem and it is difficult to solve by naive enumeration algorithms. By exploiting the properties of pure strategy and multilinear terms in the payoff functions, this paper formulates a new mixed 0-1 linear program for computing all pure-strategy Nash equilibria. To our knowledge, it is the first method to formulate a mixed 0-1 linear programming for pure-strategy Nash equilibria and it may work well for similar problems. Numerical results show that the approach is effective and this method can be easily distributed in a distributed way.
This paper considers the design of an H ∞ controller for tool point control of a hydraulically actuated knuckle boom crane. The paper describes the modelling of the crane's mechanical and hydraulic systems and a disturbance model. These are linearised and combined in a state-space model used for the controller design. The controller synthesis problem is to design (if possible) an admissible controller that solves the problem of robust regulation against step inputs with an H ∞ constraint based on the internal model principle. Simulation results are given to show the effectiveness of the method.
Various areas of research need to be considered in order to establish a mathematical model of a vehicle crash. To enhance the modeling process, a novel ANFIS-based approach to reconstruct behavior of impacting vehicles is presented in this paper. Kinematics of center of gravity (COG) a vehicle involved in an oblique barrier collision is reproduced by application of a five-layered ANFIS structure. Then, the same ANFIS system is used to simulate a different collision type than the one which was used in the training stage. The points of interests are selected to be the locations of accelerometers mounting. The accuracy of the proposed method is evaluated by the comparative analysis with the reference measurements from full-scale vehicle collisions.
