• Journal of Institute of Control, Robotics and Systems
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• 제8권9호
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• pp.764-775
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• 2002

A kinematic and dynamic optimal design of a new parallel-type rolling mill based upon Stewart platform manipulator is investigated. To provide sufficient degrees-of-freedom in the rolling process and the structural stability of each stand, a parallel manipulator with six legs is considered. The objective of this new parallel-type rolling mill is to permit an integrated control of the strip thickness, strip shape, pair crossing angle, uniform wear of the rolls, and tension of the strip. By splitting the weighted Jacobian matrices Into two parts, the linear velocity, angular velocity, force, and moment transmissivities are analyzed. A manipulability measure, the ratio of the manipulability ellipsoid volume and the condition number of a split Jacobian matrix, is defined. Two kinematic parameters, the radius of the base and the angle between two neighboring Joints, are optimally designed by maximizing the global manipulability measure in the entire workspace. The maximum force needed in the hydraulic actuator is also calculated using the structure determined through the kinematic analysis and the Plucker coordinates. Simulation results are provided.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.296-300
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• 2004

A new MR cylinder with built-in valves using MR fluid (MR valve) is proposed for fluid power control systems. The MR or Magneto-Rheololgical fluid is a newly developed functional fluid whose obvious viscosity is controlled by the applied magnetic field intensity. The MR cylinder is composed of cylinder with small clearance and piston with electromagnet. The differential pressure is controlled by the applied magnetic field intensity. It has the characteristics of simple, compact and reliable structure. The size of MR cylinder and piston has ${\varphi}$60mm${\times}$259mm and ${\varphi}$58mm${\times}$136.5mm in face size respectively and 0.8mm in gap length. Through experiments on the static characteristics, it is found that the differential pressure is controlled by the applied magnetic field intensity under little influence of the flow rate, which corresponds to a pressure control valve. Effectiveness of the MR cylinder is demonstrated through the position control of one link MR manipulator.

• International Journal of Control, Automation, and Systems
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• 제6권5호
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• pp.639-650
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• 2008

Electricity price forecasting has become an integral part of power system operation and control. In this paper, a wavelet transform (WT) based neural network (NN) model to forecast price profile in a deregulated electricity market has been presented. The historical price data has been decomposed into wavelet domain constitutive sub series using WT and then combined with the other time domain variables to form the set of input variables for the proposed forecasting model. The behavior of the wavelet domain constitutive series has been studied based on statistical analysis. It has been observed that forecasting accuracy can be improved by the use of WT in a forecasting model. Multi-scale analysis from one to seven levels of decomposition has been performed and the empirical evidence suggests that accuracy improvement is highest at third level of decomposition. Forecasting performance of the proposed model has been compared with (i) a heuristic technique, (ii) a simulation model used by Ontario's Independent Electricity System Operator (IESO), (iii) a Multiple Linear Regression (MLR) model, (iv) NN model, (v) Auto Regressive Integrated Moving Average (ARIMA) model, (vi) Dynamic Regression (DR) model, and (vii) Transfer Function (TF) model. Forecasting results show that the performance of the proposed WT based NN model is satisfactory and it can be used by the participants to respond properly as it predicts price before closing of window for submission of initial bids.

• Journal of Korea Multimedia Society
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• 제4권3호
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• pp.197-204
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• 2001

In order to increase the performance of spatial database systems, a spatial indexing method is necessary to manage spatial objects efficiently in both dynamic and static environments. A spatial indexing method considering a spatial locality is required to increase the retrieval performance. And the spatial locality is related to the location property of objects. The previous spatial indexing methods did not consider the circular location property of objects. In this paper, we introduce the CR-Tree that is a spatial index structure for clustering spatially adjacent objects in which a search space is constructed with the circular and linear domains. Using a spatial index structure considered a circular location property of objects, we show that high hit ratio and bucket utilization are increased through the simulation.

• Journal of Institute of Control, Robotics and Systems
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• 제7권8호
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• pp.664-674
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• 2001

In this paper, as a new category of fuzzy-neural networks architecture, we propose Fuzzy Polynomial Neural Networks (FPNN) and discuss a comprehensive design methodology related to its architecture. FPNN dwells on the ideas of fuzzy rule-based computing and neural networks. The FPNN architecture consists of layers with activation nodes based on fuzzy inference rules. Here each activation node is presented as Fuzzy Polynomial Neuron(FPN). The conclusion part of the rules, especially the regression polynomial, uses several types of high-order polynomials such as linear, quadratic and modified quadratic. As the premise part of the rules, both triangular and Gaussian-like membership functions are studied. It is worth stressing that the number of the layers and the nods in each layer of the FPNN are not predetermined, unlike in the case of the popular multilayer perceptron structure, but these are generated in a dynamic manner. With the aid of two representative time series process data, a detailed design procedure is discussed, and the stability is introduced as a measure of stability of the model for the comparative analysis of various architectures.

• Journal of Advanced Navigation Technology
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• 제18권5호
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• pp.501-507
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• 2014

A dynamic system is called positive if any trajectory of the system starting from non-negative initial states remains forever non-negative for non-negative controls. In this paper, new sufficient conditions for asymptotic stability of the interval positive time-varying linear discrete-time systems with time-varying delay in states are considered. The considered time-varying delay time has an interval-like bound which has minimum and maximum delay time. The proposed conditions are established by using a solution bound of the Lyapunov equation and they are expressed by simple inequalities which do not require any complex numerical algorithms. An example is given to illustrate that the new conditions are simple and effective in checking stability for interval positive time-varying discrete systems.

• Transactions of the Korean Society of Automotive Engineers
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• 제15권2호
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• pp.165-174
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• 2007

Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

• Steel and Composite Structures
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• 제23권3호
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• pp.285-302
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• 2017

Buckling-restrained braced frames (BRBFs) are commonly used as the lateral force-resisting systems in building structures in the seismic regions. The nearly-symmetric hysteretic response and the delayed brace core fracture of buckling-restrained braces (BRBs) under the axial cyclic loading provide the adequate lateral force and deformation capacity to BRBFs under the earthquake excitation. However, the smaller axial stiffness of BRBs result in the undesirable higher residual drift response of BRBFs in the post-earthquake scenario. Two alternative approaches are investigated in this study to improve the elastic axial stiffness of BRBs, namely, (i) by shortening the yielding cores of BRBs; and (ii) by reducing the BRB assemblies and adding the elastic brace segments in series. In order to obtain the limiting yielding core lengths of BRBs, a modified approach based on Coffin-Manson relationship and the higher mode compression buckling criteria has been proposed in this study. Both non-linear static and dynamic analyses are carried out to analytically evaluate the seismic response of BRBFs fitted with short-core BRBs of two medium-rise building frames. Analysis results showed that the proposed brace systems are effective in reducing the inter-story and residual drift response of braced frames without any significant change in the story shear and the displacement ductility demands.

• Journal of Institute of Control, Robotics and Systems
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• 제18권4호
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• pp.353-358
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• 2012

Human detection is a challenging task in many fields because it is difficult to detect humans due to their variable appearance and posture. Furthermore, it is also hard to track the detected human because of their dynamic and unpredictable behavior. The evaluation speed of method is also important as well as its accuracy. In this paper, we propose unified detection and tracking method for humans using Gaussian-PSO (Gaussian Particle Swarm Optimization) with the HOG (Histograms of Oriented Gradients) features to achieve a fast and accurate performance. Keeping the robustness of HOG features on human detection, we raise the process speed in detection and tracking so that it can be used for real-time applications. These advantages are given by a simple process which needs just one linear-SVM classifier with HOG features and Gaussian-PSO procedure for the both of detection and tracking.

• Journal of Institute of Control, Robotics and Systems
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• 제18권4호
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• pp.295-301
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• 2012

This paper deals with the design of robust DSMC (Discrete-Time Sliding Mode Control) scheme in order to overcome system uncertainty in steering system with mechanically joined structure. The proposed control scheme is one of robust control schemes based on system dynamics. Therefore, system dynamics required is not obtained from physical law but SCM (Signal Compression Method) through experiment in order to avoid complicate mathematical development and save time. However, SCM has a shortcoming that is the limitation of with $2^{nd}$ order linear model which does not include the dynamic of high-frequency band. Thus, considering system uncertainty, DSMC is designed. In addition, to reduce the chattering problem of DSMC, DSMC is derived from the reaching law and the Lyapunov stability condition. It is found that the proposed control scheme has robustness in spite of the perturbation of system uncertainty through computer simulation.