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Control Systems Technology, IEEE Transactions on

Issue 2 • Date March 1998

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Displaying Results 1 - 17 of 17
  • Guset Editorial

    Publication Year: 1998 , Page(s): 133
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    Freely Available from IEEE
  • Improvements in product quality in tandem cold rolling using robust multivariable control

    Publication Year: 1998 , Page(s): 257 - 269
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    This paper considers the gauge control problem in tandem cold rolling. A robust multivariable solution is proposed via the H loop shaping method of McFarlane and Glover (1990), which combined with a gain scheduling technique enables the control of the mill from thread speed to full speed. Improvement over a representative industrial controller is observed from nonlinear simulation results View full abstract»

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  • Neural-network feedback control of an extrusion

    Publication Year: 1998 , Page(s): 180 - 187
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    This work is concerned with the feedback control of microstructure during one of the simplest metal forming operations: round-to-round extrusion. Physically based semiempirical models of the microstructural dynamics are available, but they require flow variables such as strain, strain rate, and temperature as inputs. Direct measurement of these quantities inside the deforming material is not feasible, so such models alone do not define a feedback controller. In the study presented, the mapping from the temperature of the material flowing through the die to the ram load is estimated via finite-element simulation. The ram load can be measured, and so this mapping, composed with the microstructural model, does close the loop, but the simulation is far too slow for real-time implementation. This problem is addressed by training an artificial neural network to represent the simulation output. This approach is demonstrated on the simulated extrusion of a plain carbon steel rod View full abstract»

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  • H control of molten steel level in continuous caster

    Publication Year: 1998 , Page(s): 200 - 207
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    A design of the H controller for the molten steel level in a continuous caster is described. The controller design is considered to balance both the disturbance rejection and the robust stabilization. The adopted design has the input weight functions for the disturbances to adjust the closed-loop characteristics in the medium frequencies. The numerical examples show that the result of the adopted H controller had better performances than the conventional design without the input weight functions. The results of the experimental tests show that the level fluctuation by the proposed H controller was lower compared with that by the conventional proportional integral derivative (PID) controller View full abstract»

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  • Extrusion process control: modeling, identification, and optimization

    Publication Year: 1998 , Page(s): 134 - 145
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Our work has been focused on developing a methodology for process control of bulk deformation-specifically, extrusion. A process model is required for control. We state the difficulties which exist with currently available models. An appropriate decomposition and associated assumptions are introduced which permit a real-time process model to be constructed via spectral approximation to solve the axi-symmetric two-dimensional (2D) transient heat conduction equation with heat generation and loss. This solution, simulation results, and model execution times are provided. We use this model development plus output relationships from previous model development work to develop parameter identification and open-loop control methodologies. These methodologies are motivated by the structure and properties of the developed model. We demonstrate that the parameters and control variables enter into the model equations so that the identification and open-loop optimization problems are tractable. An example with plant trial data is provided View full abstract»

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  • Application of iterative learning control to coil-to-coil control in rolling

    Publication Year: 1998 , Page(s): 281 - 293
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Iterative learning control is a feedforward control technique applied to systems or processes that operate in a repetitive fashion over a fixed interval of time to improve tracking/regulation performance in response to reference inputs/disturbance inputs that are repeatable in each cycle. In this paper, learning control is applied to coil-to-coil gauge and tension control during the thread-up phase of a single stand cold mill, to compensate for disturbances caused by the variation of roll bite friction. Simulations are carried out to demonstrate the effectiveness of learning control View full abstract»

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  • Model-based control of strip temperature for the heating furnace in continuous annealing

    Publication Year: 1998 , Page(s): 146 - 156
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    Presents the model of the heating furnace in continuous annealing processes for use in design of self-tuning control systems. A simplified mathematical model is derived from first principles. The model parameters are recursively estimated with an algorithm called recursive parameter estimation with a vector-type variable forgetting factor (REVVF). The REVVF algorithm was developed for such cases where some knowledge on parameter variability can be obtained beforehand. The control system of strip temperature presented here is hierarchical. The upper level is called “optimal preview control”, which performs preset control. It previews the approaching setup change, which is the change of strip size or reference temperature, and optimizes the line speed and the strip temperature trajectory. Next, the lower level is called “temperature tracking control”, which performs closed-loop control using the above trajectory as the control target. At this level, the generalized pole-placement self-tuning control was first employed; and later, the generalized predictive self-tuning control was introduced. These control methods were applied with some practical modifications and with the above mentioned REVVF. The control has been working successfully in several real plants View full abstract»

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  • Multivariable controller design for a hot rolling mill

    Publication Year: 1998 , Page(s): 304 - 312
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    This paper describes a controller design for a hot rolling mill. The main purpose of the algorithm is to improve the control of the cross-width thickness profile of the plates. This is obtained by designing a controller which makes independent thickness control possible at the two sides of the rolling mill. This is achieved by first linearizing the positioning systems using feedback linearization and then using linear quadratic eigenspace design on the linearized multivariable system. Integral control is included to ensure zero stationary thickness error. The design is done using derived dynamical multivariable models. To ensure that the design is stable, the stability of the system is investigated using the small gain theorem. The performance of the controller is evaluated using models estimated from data obtained from the hot plate mill at The Danish Steel Works Ltd View full abstract»

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  • Controller design for hot strip finishing mills

    Publication Year: 1998 , Page(s): 208 - 219
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    The results to date of a collaborative research project with BHP Steel in Port Kembla, Australia, are described. The project is concerned with control of strip tension and looper angle in BHP's hot strip steel rolling mill (the finishing mill). The new controllers have been successfully implemented on the process and now handle all the production at the mill. The paper describes a model of the process, similar to that reported in the work of others. The development of a full nonlinear controller is traced, based on a recursive nonlinear method (cf., backstepping). Insights are drawn into possible system structures, particularly in the output feedback case when tension measurements may not be available. Alternative controller schemes are examined, including a speculative design which contains filters, similar to those obtained from output feedback designs of linear systems, together with nonlinear operators which invite comparisons with variable structure designs. Simulation results, which provided the justification for the final implementation, together with results from actual production records are presented View full abstract»

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  • Toward intelligent machining: hierarchical fuzzy control for the end milling process

    Publication Year: 1998 , Page(s): 188 - 199
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The difficulties in implementing adaptive and other advanced control schemes in industrial machining processes have encouraged researchers to combine the utilization of one hierarchical level, a fuzzy control algorithm, and robust sensing systems. The main idea of this paper deals with self-regulating controllers (SRCs). The control signal's scaling factor (output scaling factor) is self-regulated during the control process, and it can assure the optimum gain setting for the hierarchical fuzzy controller. An important role in this strategy is performed by a robust sensing system based on current sensors. For comparison, the CNC-PLC's own control loops, a hierarchical fuzzy controller based on look-up tables, and the hierarchical fuzzy controller with a self-regulating output scaling factor GC are studied. The performances of these controllers are compared. The results indicate that the hierarchical fuzzy controller with a self-regulating output scaling factor yields the best performances among them. The index known as the metal removal rate is increased, and the in-process time is reduced by 50%. Thus, higher production rates are obtained. The hierarchical fuzzy controller is equipped with three basic requirements: flexibility, low cost, and compatibility with any CNC manufacturer View full abstract»

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  • Monitoring and failure diagnosis of a steel strip process

    Publication Year: 1998 , Page(s): 294 - 303
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    This paper deals with condition monitoring and failure diagnosis of a steel strip rinsing process. Modeling and identification of the process is based on a priori knowledge about the process and data from the process. In the model, the worn parts are modeled explicitly and estimated online by an extended Kalman filter. The parameter estimation is used for supervision and as an advisory system for the process operators to decide which worn parts should be changed at the next planned stop. In addition to the normal wear, other types of abrupt failures may suddenly occur. It is not possible to detect these failures directly and the failures will give a biased parameter estimate and mislead the process operators into thinking that a part subject to wear should be changed although it is performing well. Therefore, the condition monitoring system is complemented with a fault detection and diagnosis system, which distinguishes normal wear from sudden abrupt failures View full abstract»

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  • Control of semicontinuous aluminum casting process

    Publication Year: 1998 , Page(s): 233 - 245
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    In a semicontinuous casting process, the metal level is controlled by the inflow of liquid metal. The quality of the cast product depends on the accuracy of the mold level control. There is a need for a control strategy giving better results than the fixed parameter controller and simple enough to be implemented on the existing control structure, in order to avoid a complete recommissioning of the mold level control system. This paper describes a methodology for the modeling and control of this process, based on the Kessler-Landau-Voda (KLV) method for the autocalibration of proportional integral derivative (PID) controllers. The implementation on an industrial prototype unit at Pechiney Research Center led to improved closed-loop performances (and subsequently, to quality improvement of the cast product) and better understanding of the technological process itself View full abstract»

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  • Application of fuzzy logic control for continuous casting mold level control

    Publication Year: 1998 , Page(s): 246 - 256
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    This paper deals with the problem of molten metal level control in continuous casting. Under normal circumstances, proportional integral derivative (PID) control performs quite well, but abnormal conditions (in particular nozzle clogging/unclogging) require manual intervention. Indeed, when the flow of matter into the mold increases suddenly, the PID controller is not always able to prevent large level variations that can even lead to mold overflow. So, a fuzzy controller has been designed using the expert knowledge of the operators for controlling the process during disturbed phases. The paper discusses both the design of the fuzzy logic controller and its integration with the PID in a global control architecture. Results from simulation and successful online implementation are presented View full abstract»

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  • Adaptive sigmoidal molten metal pouring control

    Publication Year: 1998 , Page(s): 270 - 280
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    We present a new adaptive nonlinear controller for vision-based molten metal automatic pouring. We describe the challenges, modeling, identification, and control of the process. Attempts to employ proportional integral (PI) and proportional integral derivative (PID) controllers were partially successful. An adaptive sigmoidal controller improved the control quality due to its variable gain and bias. The design has been successfully implemented by the Inductotherm Corp. in a new automatic pouring system named VISIPOUR View full abstract»

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  • The analysis and design of spatial control systems in strip metal rolling

    Publication Year: 1998 , Page(s): 220 - 232
    Cited by:  Papers (12)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Commercial pressures on metal strip manufacturers drive ever greater demands on the control of residual stress distributions within the finished strip. Rolling mills in current use have a range of actuators available to attempt this control and new designs are being offered with arrays of similar actuators distributed across the width of the mill. The interaction of these actuators motivates a thorough analysis of spatial control in strip metal rolling. This paper takes theory that has been successfully applied to the paper and plastics industry and applies it for the first time to the strip rolling process, giving a toolkit for the analysis and design of current and future cross-directional control systems. Data from a state of the art commercial mill is used to allow characterization of typical error signals in terms of orthogonal basis functions. Actuators are analyzed to show how much power they have within the “spectrum” of this basis function expansion. Sensors are analyzed to show their filtering effect within the spectrum. The consequent theory is used to give a rationale to future actuator design and a benchmark for the assessment of control performance with existing actuators. Two control strategies are investigated and compared-minimum variance and mini-max-and their achievements characterized. Control system sensitivity is assessed View full abstract»

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  • Development of an optimal crown/shape level-2 control model for rolling mills with multiple control devices

    Publication Year: 1998 , Page(s): 172 - 179
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Three development stages of an online crown/shape control model are discussed. Each stage bears specific consideration and provides variable information for mill operations. Theoretical derivation of the first stage facilitates understanding of mill rolling behavior. Usage of the crown/shape model leads to the development of the linear crown control system. The second-stage development is to generate an offline simulation model which bridges the gap between theory and application. It is used to verify the theoretical model, to determine control gain factors, and even to examine stability of the control algorithm. The real-time process model is last when conducting mill setup calculations. It has to cope with uncertainties of measured devices, possible errors of the theoretical model, and real-world disturbance of mill operating conditions. Providing a stable, optimal, and accurate setup for the mill is its major responsibility. Statistical methods are used everywhere in these models from tuning to optimizing processes. This optimal linear crown/shape control system has been successfully applied to a production hot strip mill since 1992. The article describes development and application of this rolling model View full abstract»

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  • On the AlF3 and temperature control of an aluminum electrolysis cell

    Publication Year: 1998 , Page(s): 157 - 171
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    We propose a control strategy for excess AlF3 and bath temperature of a prebake aluminum electrolysis cell based on analyses of measured data and studies of a simple dynamic model. Model validation indicates that there are dynamics that the model does not capture, and hence, we use real data of excess AlF3 and bath temperature to estimate AlF3 and energy disturbances, respectively. The estimation results show that the energy disturbance is the dominating disturbance. Hence, the proposed control strategy is based on an almost constant AlF3 input close to average consumption and energy manipulations to compensate for the disturbances. This requires the possibility for the resistance reference to be reduced without decreasing the current efficiency. Compared to present control strategies, this introduces an additional degree of freedom in the controller. The proposed control strategy may imply a significant economic potential through increased and stabilized current efficiency, reduced and stabilized energy consumption, reduced consumption of expensive additives, and prolongation of cell life View full abstract»

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