Research on an external adjustment method for RPECT roll profiles based on the segmented cooling principle

Roll profile electromagnetic control technology (RPECT) is a new strip flatness control technology that changes roll gap shape by controlling the roll profiles of electromagnetic control rolls (ECRs). To address the randomness of the flatness defect locations, this paper proposes an external adjustment method for RPECT roll profiles based on the segmented cooling principle. Based on the layout of the cooling areas and electromagnetic sticks, an electromagnetic-thermal-structural coupled model is established to analyse roll profile variations. The results show that symmetrically changing the cooling intensities of the different cooling areas can increase or decrease the roll crown of the ECR, while asymmetrically changing the cooling intensities of the different cooling areas can change the position of the maximum bulging point of the ECR. Variations in the component cooling ratio coefficient impact the effects of different cooling strategies, which needs to be considered when selecting the cooling strategy configuration scheme. Compared the maximum bulging values, radial temperature gradients and axial temperature gradients of different electromagnetic stick (ES) structures, the regulation law reverses when the length of the ES is too small, and the variation of the law is very small. Therefore, different ES structures have different segmented cooling regulation characteristics.

Study On Setting Method of Flatness Target Curve of SUNDWIG 20-High Mill Considering Target Crown

The flatness target curve is important in the flatness control theory. The accuracy of flatness target curve is an important factor to determine the load of flatness control means and flatness quality. Aiming at the defect that crown of each pass after rolling cannot be controlled quantitatively in the traditional target curve formulation of cold rolling, a new method considering the target crown was proposed. Specifically, the target crown of each pass can be set by combining the total proportional crown change in hot rolling field to each pass and the instability discrimination model in cold rolling field. the total proportional crown change of incoming material and finished product is allocated to each pass, and the instability discrimination model is applied to ensure the stability of the plate. The purpose of new method is to control of the crown of each pass quantitatively, so that the flatness and thickness of plate can meet the production requirements. Taking SUNDWIG 20-high mill and typical rolling products as an example, the simulation results show that, on the basis of ensuring the flatness and obtaining the minimum available crown after rolling, the model can make the flatness and crown meet the production requirements at the same time and control the crown of each pass after rolling quantitatively by setting the target crown of each pass.

Experimental Validation and Numerical Simulation of Flexible and Micro-scale Roll Gap Control Technology

To obtain a better ability of strip flatness control, this paper proposes a new flexible and micro-scale roll gap control technology. According to the principle of roll profile electromagnetic control technology (RPECT), a new electromagnetic control rolling mill with the function of roll profile control and large diameter ratio rolling is designed and built. To analyze the flatness control ability of this mill, a comprehensive finite element model (FEM) is established and verified, which includes a FEM for predicting the electromagnetic control roll profile and a FEM of rolling process. The simulation results show that the crown control ability of RPECT is stronger than the quadratic crown control ability, and the effect of tension on the roll gap shape crown is small. The results in the indentation experiment and the rolling experiment show that increasing the roll crown of electromagnetic control roll can adjust the strip shape form edge wave to non-wave, and middle wave. The feasibility of using RPECT to adjust the roll gap shape has been verified, and the roll gap control goal of uniform transverse size distribution can be achieved.

Collaboration Strategy Based on Conflict Resolution for Flatness Actuator Group

During the flatness control process, there are frequently some uncoordinated regulating behaviors in the flatness actuator group. This has a bad influence on the flatness control accuracy and the flatness control efficiency. Therefore, a collaboration strategy based on conflict resolution for the flatness actuator group has been proposed in this paper. First of all, the feature of flatness measurement value is extracted through establishing the actual flatness condition discriminating factor. After that, the coordination cooperation that is appropriate to the actual flatness condition is developed for the flatness actuator group. Finally, the optimal adjustment of the actuator population is solved by the coordinated algorithm of Topkis-Veinott and genetic algorithm collaborative optimization. The collaboration strategy proposed in this paper has been successfully applied to a flatness control system of a 1450 mm five-stand cold rolling mill.

Observer-based tracking control for single machine infinite bus system via flatness theory

In this research, we aim to use the flatness control theory to develop a useful control scheme for a single machine connected to an infinite bus (SMIB) system taking into account input magnitude and rate saturation constraints. We adopt a fourth-order nonlinear SMIB model along an exciter and a turbine governor as actuators. According to the flatness-based control strategy, first we show that the adopted nominal SMIB model is a flat system. Then, we develop a full linearizing state feedback as well as an outer integral-type loop to ensure suitable tracking performances for the power and voltage as well as the angular velocity outputs. We assume that only the angular velocity of the generator is available to be measured. So, we provide a linear Luenberger observer to estimate the remaining states of the system. Also, the saturation nonlinearities are transferred to the linear part of the system and they are canceled out using their estimations. The efficiency and usefulness of the proposed observer-controller against faults are illustrated using simulation tests in Eurostag and Matlab. The results show that the clearing critical time of the introduced methodology is larger than the classical control approaches and the proposed observer-based flatness controller exhibits over much less control energy compared to the classic IEEE controllers.

Analysis of the Thermal-force Roll Profile Control Ability Under Different Hole Structures and Slot Structures in the RPECT

Roll profile electromagnetic control technology (RPECT) is a strip flatness control technology based on the flexible control of roll profiles. As the core component, electromagnetic sticks can bulge with the induction heating of induction coils. To ensure the integrity of the coil circuit, the surfaces of the electromagnetic sticks need to be provided with slots. Moreover, the inner hole of the electromagnetic control roll is also needed to install the electromagnetic stick in the roll. The structures of the inner hole and slots affect the local structure of the electromagnetic stick and the electromagnetic control roll and then change the roll profile control ability. To research the radial bulging ability, the roundness of bulging, and the composition between the thermal crown and force crown under different holes or slots, a finite element model of circumferential RPECT is established by using the finite element software MARC. After analysis, the results showed that the radial bulging ability and the roundness under the influence of the roll radius were larger than those under the influences of the slot radius and slot amount, and the composition characteristics of the comprehensive roll profile were different under different conditions. Therefore, to achieve accurate roll profile control, the influences of the structures of holes and slots need to be included in the RPECT index.

Research on roll profile electromagnetic control ability in optimal electromagnetic stick parameter

Roll profile electromagnetic control technology (RPECT) is a new strip flatness control technology. As the control element, electromagnetic sticks have a great effect on the control ability of RPECT. To improve control ability and extend service life, effective control ratio of electromagnetic stick is presented in this paper. The ratio is designed based on the structure character of electromagnetic stick, and can be used to evaluate the key parameter of electromagnetic stick. Based on the coupled FEM, the heat flux density of the roll inner hole and the temperature distribution of electromagnetic stick are analyzed for different effective control ratios; the average contact pressure between electromagnetic stick and electromagnetic control roll is studied to evaluate the change of force roll profile; the state of roll profile and the stress state of the roll are researched to analyze the comprehensive control ability. Through the verification on the roll profile electromagnetic control experimental platform, the reasonable selection range of effective control ratio, which can be used to expand the roll profile axial affected area, is from 0.5 to 0.583. In order to increase the roll crown, the selection of ηd needs to consider the current density and the optimal selection range of effective control ratio.