• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.469-476
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• 2005

To date, many viable smart base isolation systems have been proposed. In this study, a novel friction pendulum system (FPS) and an MR damper are employed as the isolator and supplemental damping device, respectively. A fuzzy logic controller (FLC) is used to modulate the MR damper. A genetic algorithm (GA) is used for optimization of the FLC. The main purpose of employing a GA is to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. To this end, a GA with a local improvement mechanism is applied. Neuro-fuzzy models are used to represent dynamic behavior of the MR damper and FPS. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can find appropriate fuzzy rules and the GA-optimized FLC outperforms not only a passive control strategy but also a human-designed FLC and a conventional semi-active control algorithm.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1077-1099
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• 2016

One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the force-displacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quake-induced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.

• Smart Structures and Systems
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• v.19 no.4
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• pp.341-350
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• 2017

Based on the super elastic properties of the shape memory alloy (SMA) and the inverse piezoelectric effect of piezoelectric (PZT) ceramics, a kind of hybrid semi-active control device was designed and made, its mechanical properties test was done under different frequency and different voltage. The local search ability of genetic algorithm is poor, which would fall into the defect of prematurity easily. A kind of adaptive immune memory cloning algorithm(AIMCA) was proposed based on the simulation of clone selection and immune memory process. It can adjust the mutation probability and clone scale adaptively through the way of introducing memory cell and antibody incentive degrees. And performance indicator based on the modal controllable degree was taken as antigen-antibody affinity function, the optimization analysis of damper layout in a space truss structure was done. The structural seismic response was analyzed by applying the neural network prediction model and T-S fuzzy logic. Results show that SMA and PZT friction composite damper has a good energy dissipation capacity and stable performance, the bigger voltage, the better energy dissipation ability. Compared with genetic algorithm, the adaptive immune memory clone algorithm overcomes the problem of prematurity effectively. Besides, it has stronger global searching ability, better population diversity and faster convergence speed, makes the damper has a better arrangement position in structural dampers optimization leading to the better damping effect.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.7
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• pp.875-880
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• 2007

Scientific challenges in the field of MR(magnetorheological) fluids and devices consist in the development of MR devices, the mathematical modeling and simulation of MR devices, and the development of (optimal) control algorithm for MR device systems. To take a maximum advantage of MR fluids in control applications a reliable mathematical model, which predicts their nonlinear characteristics, is needed. A inverse model of the MR device is required to calculate current(or voltage) input of MR damper, which generates required damping force. In this paper, we implemented test a bench for shear mode rotary MR damper and laboratory tests were performed to study the characteristics of the prototype shear-mode rotary MR damper. The direct identification and inverse dynamics modeling for shear mode rotary MR dampers using multi-layer neural networks are studied.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.12
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• pp.1141-1146
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• 2014

As life expectancy becomes longer, reduction of human muscular strength threatens quality of human life. Many robotic devices have thus been developed to support and help human daily life. This paper deals with a new type of in-wheel actuator that can be effectively used for the robotic devices. BLDC motor, drive board, brake, ARS (Attribute Reference System), and torque sensor are combined in the single actuator module. The torque sensor is used to recognize human intention and the in-wheel actuator drives walking aids in our system. Its feasibility was tested with the active walking aid device equipped with the in-wheel actuator. Based on it, we designed an admittance filter algorithm to react on uphill and downhill drive. By adjusting mass, damping, and spring parameters in accordance with the ARS output, it provided convenient drive to the old on uphill and downhill walks.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.63-71
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• 2002

This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semi-active control strategy focusing on inclusion of effects of control-structure interaction. This benchmark problem focuses on a cable-stayed bridge in Cope Girardeau, Missouri, USA, for which construction is expected to be completed in 2003. Seismic considerations were strongly considered in the design of this bridge due to the location of the bridge in the New Madrid seismic zone and its critical role as a principal crossing of the Mississippi River. In this paper, magnetorheological(MR) fluid dampers are proposed as the supplemental damping devices, and a clipped-optimal control algorithm is employed. Several types of dynamic models for MR fluid dampers, such as a Bingham model, a Bouc-Wen model, and a modified Bouc-Wen model, are considered, which are obtained from data based on experimental results for full-scale dampers. Because the MR fluid damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results show that the performance of the proposed semi-active control strategy using MR fluid dampers is quite effective.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.33-41
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• 2020

The landing gear of an aircraft is a device that absorbs and dissipates shock energy transmitted from the ground to the fuselage. Among the landing gears, the semi-active MR damper landing gear is supposed to show high-shock absorption efficiency under various landing conditions and secure the stability when out of control. In the case of the MR damper landing gear using an annular channel rather than orifice, Amesim, a commercial multi-physics program, is considered as more useful than the conventional two-degree-of-freedom model because the damping force generated by the pressure drop through the flow annular path can cause cavitation in the low-pressure chamber of the MR damper with a specific internal structure. In this paper, the main dynamic characteristics of the MR damper landing gear with an annular type flow path structure has been analyzed under the condition of cavitation. Based on the analysis results using Amesim, a design guideline for the MR damper flow path that prevents cavitation has been proposed based on the modification of the arrangement of internal components of the damper. The guideline was verified through a drop simulation.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.37-46
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• 2005

To date, many viable smart base isolation systems have been proposed and investigated. In this study, a novel friction pendulum system (FPS) and an MR damper are employed as the isolator and supplemental damping device, respectively, of the smart base isolation system. A fuzzy logic controller (FLC) is used to modulate the MR damper because the FLC has an inherent robustness and ability to handle non linearities and uncertainties. A genetic algorithm (GA) is used for optimization of the FLC. The main purpose of employing a GA is to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. To this end, a GA with a local improvement mechanism is applied. This method is efficient in improving local portions of chromosomes. Neuro fuzzy models are used to represent dynamic behavior of the MR damper and FPS. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can find optimal fuzzy rules and the GA optimized FLC outperforms not only a passive control strategy but also a human designed FLC and a conventional semi active control algorithm.