• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.231-242
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• 2023

A novel combinatorial type-2 adaptive neuro-fuzzy inference system (T2-ANFIS) and robust proportional integral derivative (PID) control framework for intelligent vibration mitigation of uncertain structural system is introduced. The fuzzy logic controllers (FLCs), are designed independently of the mathematical model of the system. The type-1 FLCs, have a limited ability to reduce the effect of uncertainty, due to their fuzzy sets with a crisp degree of membership. In real applications, the consequent part of the fuzzy rules is uncertain. The type-2 FLCs, are robust to the fuzzy rules and the process parameters due to the fuzzy degree of membership functions and footprint of uncertainty (FOU). The adaptivity of the proposed method is provided with the optimum tuning of the parameters using the neural network training algorithms. In our approach, the PID control force is obtained using the generalized type-2 neuro-fuzzy in such a way that the stability and robustness of the controller are guaranteed. The robust performance and stability of the presented framework are demonstrated in a numerical study for an eleven-story seismically-excited building structure combined with an active tuned mass damper (ATMD). The results indicate that the introduced type-2 neuro-fuzzy PID control scheme is effective to attenuate plant states in the presence of the structured and unstructured uncertainties, compared to the conventional, type-1 FLC, type-2 FLC, and type-1 neuro-fuzzy PID controllers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1223-1233
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• 1992

Chemical and mechanical properties of workpieces and tools are important factors for selecting machining parameters in machining process planning. As there is no universal rule representing the machinability defined by metal removal rate, the selection of machining parameters still requires experience-oriented methods. In this paper, a new approach is presented to develop mathematical models for generating optimum machinability in turning processes based on chemical and mechanical properties of workpieces. Neural-Network methodology is introduced to identify mathematical models for machinability. It is confirmed by simulations that the proposed methodology can be used for developing numerical controllers with adaptive control performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.195-203
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• 2017

This paper is concerned with the active vibration control of shell structure that is subjected to internal unbalanced excitation by using active mounts and accelerometers. The unbalanced excitation is caused by a rotating unbalanced mass. The control algorithm considered in this study is the negative acceleration feedback (NAF) control. A simplified dynamic model was derived to verify the effectiveness of the NAF control. Four actuators and four accelerometers were mounted on the shell structure, so that the multiple-input and multiple-output (MIMO) NAF controller was designed by both centralized and decentralized ways. Numerical results show that both the decentralized and centralized NAF controllers are effective. Based on the numerical simulation, the proposed decentralized NAF controller was applied to the real shell structure. Experimental results show that the proposed decentralized NAF controller can effectively suppress vibrations of the shell structure.

• The Journal of Korea Robotics Society
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• v.7 no.1
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• pp.35-44
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• 2012

This paper presents a method to optimize motion planning for industrial manipulators with redundancy. For optimal motion planning, first of all, particular inverse kinematic solution is needed to improve efficiency for manipulators with redundancy working in various environments. In this paper, we propose three kinds of methods for solving inverse kinematics problems; numerical and combined approach. Also, we introduce methods for optimal motion planning using potential function considering the order of priority. For efficient movement in industrial settings, this paper presents methods to plan motions by considering colliding obstacles, joint limits, and interference between whole arms. To confirm improved performance of robot applying the proposed algorithms, we use two kinds of robots with redundancy. One is a single arm robot with 7DOF and another is a dual arm robot with 15DOF which consists of left arm, right arm with each 7DOF, and a torso part with 1DOF. The proposed algorithms are verified through several numerical examples as well as by real implementation in robot controllers.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.37-43
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• 2002

In this paper, an integrated optimum design method for hybrid structural control system is studied. Not only the distribution and the capacity of passive devices but also those of active devices, and the controllers are treated as design variables in the proposed approach. Multi-objective optimization problem is formulated by using the preference function, which is newly defined in this study. Genetic algorithm is adopted as a numerical searching technique in order to simultaneously find the optimum solutions. The validity of the proposed method is verified through the example designs and the numerical simulations of an earthquake excited multi-degrees-of-freedom structure.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.153-158
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• 2007

Since the introduction of Nanoimprint in the mid-1990s, Nanoimprint lithography, a low-cost, non-convential method, has been the dominant lithography technology that guarantees high-throughput patterning of nanostructures. Based on the mechanical embossing mechanism, Nanoimprint lithography creates the nanopatterns on the polymer material cast on the substrate. In essence, the process needs nanofabrication equipment for printing with the adequate control of temperature, pressure and control of parallels of the stamp and substrate. This article introduce the possibility and reality of the thermal control on the hot plate using a CFD code. Numerical computation has been conducted for assessing the feasibility of a hot plate($120{\times}120\;mm2$). PID control is adopted to ensure high temperature uniformity in several zones. Parallel experiments have also been performed for verifying thermal performance. Not only show the results the optimum number of thermocouples related to controllers but also suggest that the thermal simulation using a CFD code would be an alternative method to design and develop the thermal control equipment in the financial aspect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.179-189
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• 2008

The object of this study is to develope a program with proposed numerical techniques for an optimal seismic control of structures using active tendon systems. Ricatti closed-loop algorithm has been applied to control the active tendon systems with time-delay problem. The optimal control is formulated as an optimization problem which is finding optimal weighting matrices by minimizing the quadratic performance index by SUMT. In order to find the optimal location of active tendons in structures, controllability index has been introduced. From numerical examples, the current optimal control technique with optimal location of tendons was suitable to control the seismic response of structures.

• Structural Engineering and Mechanics
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• v.52 no.2
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• pp.275-290
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• 2014

In this paper, Simple Adaptive Control (SAC) method is used to mitigate the detrimental effects of earthquakes on MR-damper equipped structures. Acceleration Feedback (AF) is utilized since measuring the acceleration response of structures is known to be reliable and inexpensive. The SAC is simple, fast and as an adaptive control scheme, is immune against the effects of plant and environmental uncertainties. In the present study, in order to translate the desired control force into an applicable MR damper command voltage, a neural network inverse model is trained, validated and used through the simulations. The effectiveness of the proposed AF-based SAC control system is compared with optimal H2/LQG controllers through numerical investigation of a three-story model building. The results indicate that the SAC controller is substantially effective and reliable in both undamaged and damaged structural states, specifically in reducing acceleration responses of seismically excited buildings.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.113-116
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• 1997

In this paper, we present a robust $H^{\infty}$ controller design method for parameter uncertain time-varying systems with disturbance and that have time-varying delays in both state and control. It is found that the problem shares the same formulation with the $H^{\infty}$ control problem for systems without uncertainty. Through a certain differential Riccati inequality approach, a class of stabilizing continuous controller is proposed. For parameter uncertainties, disturbance and time varying delays, proposed controllers the plant and guarantee an $H^{\infty}$ norm bound constraint on disturbance attenuation for all admissible uncertainties. Finally a numerical example is given to demonstrate the validity of the results.ts.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.4
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• pp.259-269
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• 2003

This paper considers the problem of determining a set of PI, PD and PID controller gains, for a given linear time invariant plant, that meets or exceeds the closed loop step response specifications. The proposed method utilizes two recent results: for a given system, (1) finding a set of stabilizing PI, PD and PID gains and (2) the relationship between time response (overshoot and speed) and the coefficients of the characteristic polynomial. The method allows us to extract a subset of PI, PD and PID gains that meets stability as well as time domain performance requirements. The intersections of two dimensional sets described by linear and quadratic inequalities in the controller design space are need to be Identified through numerical computation. The procedure is illustrated by examples.