• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.237-244
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• 2012

This paper studies the design of a two-DOF optimal controller for the strip gauge-tension of cold tandem mill processes, that uses a reference shaping filter and a disturbance observer. First, a mathematical model of the strip gauge and tension system is constructed using the gauge meter equation and Hooke's law, respectively. Next, a two-DOF controller considering of a feedforward controller and a feedback controller is designed. The former is based on the reference shaping filter and the disturbance observer, and the latter is based on the ILQ optimal control algorithm. Finally, it is shown through a computer simulation that the proposed optimal controller is able to improve the strip gauge accuracy and the tension variation more than the conventional MV-AGC controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.299-303
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• 1995

This paper charcterizes dynamics of cold tandem minns, and constructs it state-space model of which are linear time invariant, using subspace method. Step responses particularly show the influence on mass transfer delay. Input-output data set are obtained form nonlinear differential equations including mass transfer delay and nonlinearity. It is shown that the identified state-apace model well approximates the original systems dynamics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.290-302
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• 2000

In this paper, we study on the identification of discrete-time state-space model for robust control of tandem cold mill, using a MOESP(MIMO output-error state-space model identification) algorithm based on subspace method. It is shown that the identified model is well adapted to input-output data sets, which are obtained from nonlinear mathematical equations of tandem cold mill. Furthermore, deterministic H$\infty$ norm bounds on uncertainties including modeling errors and disturbances are quantitatively identified in the frequency domain. Finally, the results give a basic idea to determine weighting functions included in formulating some robust control problems of tandem cold mill.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.66-74
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• 1994

A loop-shaping LQ controller is synthesized for tandem cold mills. And a new loop- shaping technique is suggested for LQ controller design. The suggested loop-shaping LQ control system is compared with the standard loop-shaping LQ control system. The simulation results show that the theickness and interstand tension control accuracy of tandem cold mills can be improved by the compensated loop-shaping LQ controller.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.895-905
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• 1999

This paper identifies a linear time-invariant mathematical model of each stand of a five-stand tandem cold mill to design a robust $H_\infty$ thickness controller by applying input and output data sets to N4SID (Numerical algorithms for Subspace State Space System Identification) method. The input-output data sets describe interstand interference in the process of tandem cold rolling and are obtained from a nonlinear simulator of the tandem cold mill. In result, it is shown that the identified model well approximates the nonlinear model than a Taylor linearized model. Furthermore, uncertainties including roll eccentricity and incoming strip variation are quantitatively analyzed from the plot of maximum singular values.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2629-2639
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• 1994

A robust multivariable controller is synthesized for tandem cold mills. A blocked-noninteracting control method is applied for simplifying the structure of rolling control systems. And, a loop-shaping LQ control method is applied for maintaining the variation of the thickness and tension of each rolling stand as small as possible. In this paper, the effects of the design parameter on loop-shaping and the number of control inputs are evaluated. The simulation results show that the thickness and tension control accuracy of tandem cold mills can be improved by the blocked-noninteracting and compensated loop-shaping LQ controller.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2142-2153
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• 1995

A digital preview controller using optimal LQ control theory is suggested for tandem cold mills to achieve a remarkable improvement of the thickness accuracy. Optimal preview control system is constructed for each rolling stand of tandem cold mills for which the blocked noninteracting control is carried out, and it is compared with the optimal LQ control system which has only feedback control. And in the cases that all/some of disturbance inputs are previewable, full and partial preview controllers are designed, and their performance effects are compared and discussed. The simulation results show that the performance of tandem cold mills can be improved largely through partial preview control.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.114-122
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• 1995

A digital preview controller is designed for tandem cold mills to achieve a more improvement of the thickness accuracy. Simultaneously a blocked noninteracting controller is synthesized for rejecting the interactive effects among adjacent stands and for controlling independently each roll stand of tandem cold mills. The performance effects and characteristics of the suggested roll contol system are discussed in the practical viewpoint. The simulaltion results show that the thickness accuracy of tandem cold mills can be largely improved by the blocked noninteracting and digital preview controller.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.8
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• pp.78-86
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• 2000

This study identified a linear time-invariant mathematical model of each stand of a five-stand tandem cold mill. Two model identification methods are applied to construct a linear model of each stand of the tandem cold mill. For the model identification the input-output data that have interstand interference property in tandem cold rolling are obtained from a nonlinear simulator of the tandem cold mill. And a linear model of each stand is identified with N4SD(numerical algorithms for subspace state space system identification) method based on a state-space model and Least Square algorithm based on a transfer function. Furthermore a modeling error of the tandem cold mill is quantitatively analyzed from a maximum singular value plot of error function between an identified nominal model and uncertain model. In conclusion the comparison of the output signals between the existing Taylor linearized model the identified linear model and the nonlinear model of the tandem cold mill shows the accuracy and the applicability of the proposed identified model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.142-149
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• 1999

Strip profile and shape control is one of the most important technologies in cold mill, especially for ultra-thin and wide cold strip. The 6-high mills, both of HCMW and UCMW mill, are known to be very effective for the shape controllability. The optimized values of these factors for set-up scheduling were analyzed and found that excellent strip control would be possible by controlling the combination of the influencing factors according to hot coil profile. The important considerations for operation were discussed for individual stand.