Rolling Mill System Research Articles

Simulation and Experimental Study on Three-roll Rolling of Stainless Steel-Carbon Steel Cladding Rebar

In this paper, ABAQUS is used to simulate the rolling process of stainless steel (304) and carbon steel (20MnSiV) clad steel bar by three rolls. Through analysis of different three-roll pass system, KNOCKS rolling mill system is selected as the finishing pass of rolling production line. Experimental results prove that finite element simulation result is right, it can be concluded that the thickness distribution of stainless steel-carbon steel cladding rebar rolled by KNOCKS rolling mill system cladding metal is more uniform, which can provide better finished products for the final pass rolling.

Регулирование координат электромеханической системы прокатного стана на основе наблюдателя упругого момента

The paper considers the electromechanical system of the reversing stand of the plate rolling mill 5000 of PJSC “Magnitogorsk Metallurgical Plant” (PJSC “MMK”). The performed experimental studies of transient processes in the mode of gripping metal by rolls allowed establishing unacceptable dynamic loads of an oscillatory nature and a loss of controllability of the electric drive. This confirms the need for the development of control methods that limit the motor and spindle torques. It is noted that the known control systems for the speed modes of an electric drive, which decrease the elastic moment due to the preliminary closing of the angular gaps, are, in essence, open-loop speed control systems. This does not provide for the controlled regulation of coordinates in dynamic modes. The paper proposes the development of a closed system for automatic control of coordinates of a two-mass electromechanical system with an observer of the moment of the elastic shaft and the speed of the second mass. An observer of the unmeasurable parameters of a two-mass rolling mill system has been developed. It provides an indirect determination (recovery) of the roll speed and the spindle torque in on-line mode. It is based on a system of equations in the state space. By comparing the reconstructed and experimentally obtained transient processes, the satisfactory accuracy of the results has been confirmed. Based on the proposed observer, the authors developed an automatic control system (ACS) of the roll speed with subordinate contours of the elastic shaft moment, speed and engine torque. The setting of closed-loop regulators has been substantiated. Transient processes of moments and velocities are considered at impact application of a load with increased speed of the second mass speed control loop. The analysis of the LAFC and LPFC confirmed the stability of the developed system in the frequency range. The analysis of experimental data substantiated a conclusion about the influence of the angular gap on the accuracy of the elastic moment recovery in the mode of metal capture by rolls. Prospects for the introduction of developments at mill 5000 and other rolling mills operating with shock load are noted.

Adaptive Torsional Vibration Control of the Nonlinear Rolling Mill Main Drive System with Performance Constraints and Sensor Errors

This paper studies the torsional vibration suppression control problem for the nonlinear rolling mill main drive system with performance constraint requirements and unknown measurement sensitivities. Firstly, considering the nonlinear friction between the roll gaps, a torsional vibration model of the main drive system of rolling mill is established. Then, with the asymmetric performance constraints transformation, the motor torque control law is proposed based on backstepping algorithm. By introducing an adaptive bound estimation approach, the multiple unknown parameters caused by the sensor sensitivities can be approximated with very few adaptive laws. The dynamic surface technology is introduced to simplified the control design procedure and solve the computational explosion problem. It is strictly proved that the resulting closed-loop system is stable in the sense of uniformly ultimately boundedness and both transient and steady-state performances of the load speed are preserved. Finally, the simulation is provided to show the validity and the advantages of the proposed techniques.

Adaptive neural torsional vibration suppression of the rolling mill main drive system subject to state and input constraints with sensor errors

Torsional vibration often occurs in rolling mill drive system, which seriously affects the product quality accuracy and the service life of transmission equipment. This paper studies the adaptive neural torsional vibration suppression control problem for the rolling mill main drive system with state and input constraints subject to unknown measurement sensitivities. Firstly, considering the nonlinear friction between the work roll and strip, nonlinear damping at the motor and the load and unknown uncertainties on system parameters, a new torsional vibration model of the main drive system of rolling mill is established. Then, by selecting the proper asymmetric tangent barrier Lyapunov function, the motor torque control law is proposed based on backstepping algorithm. The adaptive neural networks are introduced to solve the unknown uncertainties and the unknown measurement errors and a continuous differentiable Gaussian error function is employed to deal with actuator saturation. It is strictly proved that the designed main drive torsional vibration system is stable and the performances of the transformed states are preserved. Finally, simulation shows the validity and the advantages of the proposed algorithm.

Coupled Vibration Behavior of Hot Rolling Mill Rolls under Multinonlinear Effects

A coupled vibration model of hot rolling mill rolls under multiple nonlinear effects is established by considering the nonlinear spring force produced by the hydraulic cylinder, the nonlinear friction between the work rolls, the dynamic variation of rolling force, and the effect of external excitation as well as according to the structural constraints of a four-high hot rolling mill in the vertical and horizontal directions. The amplitude-frequency response equation of rolling mill rolls is determined by using a multiple-scale approximation method. Furthermore, use of actual data for simulation indicates that the internal resonance is the main cause of coupling vibration of the rolling mill rolls. In addition, changes in the movement displacement of the hydraulic cylinder and the coupling parameters strongly affect the coupling system of the rolling mill rolls. Finally, the study of the dynamic bifurcation characteristics of the rolling mill rolls indicates that, with varying external excitation amplitude, the vibration of rolls alternates between periodic motion, period-doubling motion, and chaotic motion in both vertical and horizontal directions. This is one of the reasons for the appearance of periodic light and dark stripes on the strip surface. Furthermore, the range of the external excitation amplitude (F0) at which the rolling mill roll system vibrates violently, that is, 5.68e5 N < F0 < 5.84e5 N and F0 > 6.12e5 N, must be avoided. The research results can provide a theoretical reference for further exploration of the coupling vibration mechanism of hot rolling mills.

Hopf bifurcation control for the main drive delay system of rolling mill

In this work, the Hopf bifurcation of the main drive delay system of rolling mill is controlled and analyzed by designing a nonlinear controller. The time-delay is selected as a bifurcation parameter, and the following conclusions are obtained through analysis: (1) in the absence of state feedback control, the system will generate the Hopf bifurcation at the expense of its stability when the bifurcation parameter exceeds the threshold value; (2) in the state under feedback control, the occurrence of Hopf bifurcation is effectively delayed and the stable region of the system is also well extended. More importantly, we can change the properties of bifurcation periodic solutions by selecting the appropriate gain parameters. Some numerical simulations reveal that under the nonlinear feedback control, the vibration amplitude of the system can be effectively reduced.

A Power Drive System for Pipe Rotation and Delivery Mechanisms of a KhPT-250 Cold Rolling Mill

This article is devoted to development of synthesis of power drive system of KhPT-250 cold rolling mill. Selection procedures for process variables of the reducer, electric machine, and power circuits have been developed. It has been noted that the configuration of power circuits can decrease failures by about 30%. It has been demonstrated that, in the power drives of the KhPT-250 mill, it is required to take pipe deformability into account and the control object should be considered as a multicircuit double-mass system. It is proposed to select the gear reduction rate on the basis of the criterion of minimum oscillation. With this aim in mind, the methods of frequency synthesis have been applied to construct asymptotic frequency characteristics used for determination of the reducing gear factor in the case of a restricted amplitude of the resonance maximum. Using the finite element method, the geometrical parameters of the stator and rotor of a synchronous reluctance machine have been selected, and its weight and dimensions have been improved by about 35%. Predictions demonstrate that the best ratio of the flow longitudinal constituent to the transversal constituent is obtained for a axially laminated rotor. Implementation of a power drive system with a field regulated synchronous reluctance motor on a KhPT-250 cold rolling mill made it possible to increase the mill output by 10–15%, with the quality of rolled products improving by 20–25%. According to preliminary estimations, the annual efficiency of the power drive system will be from 2 to 5 million rubles.

Hopf bifurcation control of nonlinear electromechanical coupling main drive system of rolling mill

The nonlinear dynamic model of electromechanical coupling main drive system of rolling mill with nonlinear stiffness and frictional torque is established. The equilibrium point of the system is analyzed, the conditions of the Hopf bifurcation of the system are given, and the type of the bifurcation is studied. The Hopf bifurcation controller is obtained by using the exact feedback linearization method based on differential geometry and combining the quadratic optimal control theory. The controller does not change the type of the Hopf bifurcation, and by changing the location of the bifurcation point, the bifurcation characteristics of the nonlinear system are effectively delayed. The range of parameter that makes the equilibrium point of the system stable is increased, and the robustness and effectiveness of the controller are analyzed when the system has parameter perturbation or additive feedback control disturbance.

Modelling and dynamic surface backstepping recursive sliding mode control for the speed and tension system of the reversible cold strip rolling mill

For the speed and tension system of the reversible cold strip rolling mill, a dynamic surface backstepping recursive sliding mode control (DSBRSMC) strategy is proposed based on the immersion and invariance (I&I) adaptive method and the nonlinear disturbance observer (NDO). First, a relatively complete mathematical model for the speed and tension system of the reversible cold strip rolling mill driven by alternating current (AC) asynchronous motors is established. Next, the I&I adaptive method is adopted to estimate the system perturbation parameters, and the NDO is developed to observe the system uncertainty. Again, controllers for the speed and tension system are presented by combining the backstepping control, the dynamic surface control, and the recursive sliding mode control together. Theoretical analysis shows that the closed-loop system is stable in the Lyapunov sense. Finally, simulation research is conducted by using the actual data, and results show the validity of the proposed control strategy.

Modelling and dynamic surface backstepping recursive sliding mode control for the speed and tension system of the reversible cold strip rolling mill

Modelling and dynamic surface backstepping recursive sliding mode control for the speed and tension system of the reversible cold strip rolling mill

Diagnosis, Diagnosticability Analysis, and Test Point Design for Multiple Faults Based on Multisignal Modeling and Blind Source Separation

An effective strategy for analyzing and diagnosing multiple faults is developed, based on the concise causality structure obtained by multisignal modeling and the fault source signals extracted by blind source separation (BSS). The key idea is enlightened by the need to handle the redundant test signals and the multiple fault ambiguity groups when applying multisignal modeling for multiple fault diagnosis. Considering that BSS is inherently suitable to extract the independent source information, it is integrated into the multisignal model to reconstruct the causality structure that will have superior diagnosticability. Preliminary study on test point design is also presented in the proposed strategy. The proposed multiple fault diagnosis strategy has been verified on a hydraulic automatic gauge control simulation system in a cold rolling mill. Results show that it can use less test information to effectively diagnose all simulated single and multiple faults.

Adaptive Fuzzy Vertical Vibration Suppression Control of the Mechanical-Hydraulic Coupling Rolling Mill System With Input Dead-Zone and Output Constraints

This paper investigates the adaptive fuzzy vertical vibration suppression control problem for the six-high rolling mill system. Firstly, a new vibration model is established with the consideration of the coupling of mechanical and hydraulic systems and the unknown uncertainty on nonlinear rolling force. Then, the adaptive active control strategy is proposed to suppress chatter of the rolling mill under the input dead-zone and output constraints. The adaptive fuzzy logic systems are used to deal with the unknown nonlinear functions and the unknown system parameters. Based on the designed controller, the mechanical-hydraulic coupling rolling system is proven to be stable and the performance of the displacement of work roll is preserved. Finally, the simulation comparison shows the validity and the advantages of the proposed algorithm.

Static Model Identification for Sendzimir Rolling Mill Using Noise Corrupted Operation Data

A Sendzimir rolling mill (ZRM), one of the rolling mill systems, is a machine used to obtain a steel strip with a desired shape in cold rolling. Model based controllers are mainly used for the shape control, but it is difficult to obtain the mathematical model of the ZRM, so model identification should be used. This study proposes a method identifying static model of the ZRM. To identify the static model of the ZRM, a mill matrix (G m ) is obtained that expresses the linear relation between the actuators, and the shape of the strip and the data obtained through the ZRM's operation are used to obtain G m However, as the operation data are affected by large measurement noise, and the patterns of the multiple control inputs are not diverse, this results in an inaccurate estimation. Therefore, a data processing method using multiple valid sets of operation data is proposed to estimate G m . Additionally, a G m update method is suggested to estimate the G m whenever a single pass operation is finished, according to the static model change of the plant. The proposed method is verified by comparing the results with the real operation data. This research will be helpful in all industries that use rolling mill machines such as 4-high mill, 6-high mill, and clustering mill in hot and cold rolling.

Decoupling Predictive Control of Strip Flatness and Thickness of Tandem Cold Rolling Mills Based on Convolutional Neural Network

The control system regarding flatness and thickness of the strip in tandem cold rolling mill is generally multivariate, non-linear, and strong-coupling. In this paper, a decoupling predictive control method based on convolutional neural network is invented for the decoupling of these two elements. We at first introduce the mathematical model, namely AFC-AGC model, of the automatic control on flatness and thickness, and analyze the coupling problem between them. Then CNN with strong feature extraction ability is used to design the decoupler of the flatness and thickness system by iteratively learning of the input and output data of the control system in consideration. Next, according to the non-linearity and the pure delay of the rolling mill system, we design the flatness and thickness controller using model predictive control algorithm (MPC). Finally, the simulations and comparisons are performed on the actual parameters of a tandem cold rolling mill. Our results demonstrate the effectiveness of the proposed decoupling control method and confirm the accuracy and robustness of the modified flatness and thickness control system.

Command Filter-based Backstepping Control for the Speed and Tension System of the Reversible Cold Strip Rolling Mill Using Disturbance Observers

This paper investigates the decoupling and coordinated tracking control problem for the speed and tension system of the reversible cold strip rolling mill. Using a diagonal matrix decoupling network and neural network disturbance observers, we propose a command filter-based backstepping control strategy. First, the diagonal matrix decoupling network is constructed to weaken the coupling between the speed and tension of the rolling mill system, which reduces the complexity of the system model effectively. Second, controllers are designed by combining the backstepping with the command filter, which solves the “explosion of complexity” problem in backstepping procedure, and optimizes the system’s control structure. Next, neural network disturbance observers are developed to observe the uncertain items of the system, which improve the tracking control precision of the system effectively. Theoretical analysis shows that all signals in the closed-loop system are uniformly ultimately bounded. Finally, simulation research is carried out on the speed and tension system of a 1422 mm reversible cold strip rolling mill; results show that using the proposed control strategy increased the dynamic response speed of the system by approximately 1s, and the stability precision improved by approximately 2000 N.

Nonlinear control by backstepping applied to the web winding system

The key system in the reversible cold rolling mill is the web winding system (WWS). The WWS is a complex process characterized by multiple variables with varying parameters in time, a strong coupling and a non-linearity, various operating conditions. For many products, such as thin film tapes, highly precise control of web tension and web velocity to prevent bending or breaking of the web is of paramount importance throughout the manufacturing process. Because of the radius variation and broad range of roller inertia, the dynamic system changes strongly during the winding process. In this work, we present the design of a new version of the nonlinear backstepping control law for the WWS, in order to guarantee that the final product does not undergo deformations or breaks. It is an adaptive control approach of backstepping with introduction of integral actions. Using Lyapunov stability theory, we verify that trajectory dynamics are asymptotically stable. Simulation studies with the MATLAB/SIMULINK environment are presented to exemplify the effectiveness and performances of the proposed controllers.

Research on the Vertical Vibration Characteristics of Hydraulic Screw Down System of Rolling Mill under Nonlinear Friction

The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic screw down system of the rolling mill are studied, respectively. First, a vertical vibration model of a hydraulic screw down system was established, considering the nonlinear friction and parameter uncertainty of the press cylinder. Second, the correlation between different equivalent damping coefficient, internal leakage coefficient, proportional coefficient, vertical vibration was analyzed. The simulation results show that, in the closed-loop state, when Proportional-Integral-Derivative (PID) controller parameters are fixed, due to the change of the equivalent damping coefficient and internal leakage coefficient, the system will have parameter uncertainty, which may lead to the failure of the PID controller and the vertical vibration of the system. This study has theoretical and practical significance for analyzing the mechanism of vertical vibration of the rolling mill.

Nonlinear Backstepping Control Design using a High Gain Observer for Automatic Gauge Control

The accuracy and quality of the steel strip exit thickness depends on the structure of the automatic gauge control system (HAGCS) of reversible cold rolling mill. This structure is based on the position control of the work rolls. The design and implementation of a new HAGCS by the backstepping approach with high gain observer are discussed in this paper. Backstepping controller of HAGCS and high gain observer (HGO) has been implemented using MATLAB/SIMULINK software. The simulation results show the effectiveness of the proposed control for improving the quality of the output strip.

Non‐linear optimal control for the hot‐steel rolling mill system

Control of hot-steel rolling mills aims at raising the levels of quality of the related industrial production and at minimising the cost of the electric energy consumed by such industrial units. This paper proposes a non-linear optimal control approach for the hot-steel rolling mill system. The non-linear dynamic model of the hot-steel rolling mill undergoes approximate linearisation around a temporary operating point which is recomputed at each iteration of the control method. The linearisation relies on Taylor series expansion and on the calculation of the system's Jacobian matrices. For the approximately linearised model of the hot-steel rolling process, an H-infinity feedback controller is designed. This controller provides the solution of the non-linear optimal control problem for the system under model uncertainty and external perturbations. For the computation of the controller's feedback gain, an algebraic Riccati equation is iteratively solved at each time-step of the control method. The global asymptotic stability properties of the control method are proven through Lyapunov analysis. Finally, to implement state estimation-based control for this system, the H-infinity Kalman filter is proposed as a robust state estimator.

Parametric Robust Control of the Multivariable 2 × 2 Looper System in Steel Hot Rolling: A Comparison between Multivariable QFT and H∞

Two robust mutlivariable controllers, H∞ and a decentralized quantitative feedback theory (QFT), are designed in the frequency domain for the 2 × 2 looper system in a steel hot rolling mill to keep stability in the presence of parametric uncertainties. The H∞ controller is designed by using the mixed sensitivity approach, while the multivariable decentralized QFT is designed by the extension of the sequential loop closing method presented elsewhere. Stability robustness conditions are verified in the frequency domain, while simulations in time domain are carried out to evaluate the controllers and compare their performance along with that of proportional + integral (PI) and single input single output (SISO) QFT controllers designed earlier. The QFT controller shows the best balance among the performance indicators analyzed here; however, at the expenses of using higher power in one of the control inputs.