Dianhua Zhang

Smith Prediction Monitor AGC System Based on Fuzzy Self-Tuning PID Control

In accordance with the feature of pure delay in monitor AGC system for cold rolling mill, a new fuzzy self-tuning PID Smith prediction controller is developed. The position control model is deduced based on a single stand cold rolling mill, and the fuzzy controller for monitor AGC system is designed. The analysis of dynamic performance for traditional PID Smith prediction controller and fuzzy self-tuning PID Smith prediction controller is done by MATLAB toolbox. The simulation results show that fuzzy self-tuning PID Smith controller has stronger robustness, faster response and higher static accuracy than traditional PID Smith controller.

Actuator Efficiency Adaptive Flatness Control Model and Its Application in 1250 mm Reversible Cold Strip Mill

The existing research of the flatness control for strip cold rolling mainly focuses on the calculation of the optimum adjustment of individual flatness actuator in accordance with the flatness deviation, which is used for general flatness control. As the basis of flatness control system, the efficiencies of flatness actuators provide a quantitative description to the law of flatness control. Therefore, the determination of actuator efficiency factors is crucial in flatness control. The strategies of closed loop feedback flatness control and rolling force feed-forward control were established respectively based on actuator efficiency factors. For the purpose of obtaining accurate efficiency factors matrixes of flatness actuators, a self-learning model of actuator efficiency factors was established. The precision of actuator efficiency factors can be improved continuously by the input of correlative measured flatness data. Meanwhile, the self-learning model of actuator efficiency factors permits the application of this flatness control for all possible types of actuators and every stand type. The application results show that the self-learning model is capable of obtaining good flatness.

Algorithm Design and Application of Laminar Cooling Feedback Control in Hot Strip Mill

Feedback control is one of the most important ways to improve coiling temperature control precision during laminar cooling process. Laminar cooling equipments of a hot strip mill and structure of the control system were introduced. Feedback control algorithm based on PI controller and that based on Smith predictor were designed and tested in a hot strip mill respectively. Practical application shows that the feedback control system based on PI controller plays a limited role in improving coiling temperature control precision. The feedback control system based on Smith predictor runs stable and reliable. When the measured coiling temperature deviates from the target value, it can be adjusted to the required range quickly and steadily by Smith predictor feedback control, which improves the coiling temperature control precision greatly, and qualities of hot rolled strips are improved significantly.

Effect of initial crown on shape of hot rolled strip

Based on the influence coefficient method, the effect of entry strip crown on the shape of hot rolled strip was analyzed using the software of roll elastic deformation simulation. According to the practical condition of a domestic hot rolled strip plant, the unit strip crown change from the first stand to the last stand was calculated when the entry crown of hot strip varies. The calculated result shows that the entry strip crown does not significantly affect the target strip crown at the exit of the last finishing stand in respect to a fixed strip shape control reference (such as bending force). The calculation was analyzed, and the research is helpful in modeling strip shape setup and shape control.

Optimal multi-variable flatness control for a cold rolling mill based on a box-constraint optimisation algorithm

As the flatness control system is a multi-variable control system, the key issue for high-precision flatness is the determination of the optimal adjustments of flatness actuators. In order to determine these the first step is the establishment of a multi-variable control model in the flatness control process, by which the actual flatness control problem has been reduced to a non-linear optimisation problem with box-constraints. Around this optimisation problem, characteristics and applicability of current optimisation algorithms were analysed. Based on the coordinate descent method, a new multi-variable optimisation algorithm with global convergence was proposed. In the algorithm, the problem was transformed into a series of univariate optimisations which could be solved by sequentially searching along coordinate directions. In order to make the objective function decrease rapidly, and ensure that each iteration are carried out within the feasible region, the accelerating step method is adopted to determine the iterative step size. A series of feasible points have been obtained through a series of iterations, which make the objective function decrease gradually until the optimal solution has been obtained. Finally, the algorithm has been tested by numerical experiments with production data of actual flatness control process, and applied to the 1450 mm tandem cold mill. Numerical experiments and application show that the proposed algorithm not only can satisfy the requirements of response speed, but also have a good accuracy, which can provide a reference for the realisation of high-precision flatness control processes of cold rolled strip.

Simplified Weighted Velocity Field for Prediction of Hot Strip Rolling Force by Taking into Account Flattening of Rolls

The weighted velocity field was simplified for analysis of hot strip roling. Using the field and GM (geometric midline) yield criterion, the deformation power, friction power and shear power were obtained respectively. Summing the partial power contributions, the total deformation power for strip roling was presented. Then, by minimizing the power function, the roling force was obtained; meanwhile, considering the efect of rol elastic flattening, iterative calculation of the rol radius was carried out until the radius was convergent. On-line data were compared with the calculated results to verify the model accuracy. It was indicated that the calculated roling forces were basicaly in agreement with the measured ones since the maximumerror was less than 10? 0%. Moreover, the efects of various roling conditions such as thickness reduction, friction factor and shape factor, upon separating force, location of neutral angle, and stress state coeficient were discussed systematicaly.

Microstructure and Mechanical Properties of Semi-continuous Equal-channel Angular Extruded Interstitial-free Steel

An innovative method called semi-continuous equal-channel angular extrusion (SC-ECAE) has been developed to produce ultrafine grained steel by inducing severe plastic deformation. In contrast to the external forces that are exerted on specimens in traditional ECAE, the driving forces are applied on the dies in the novel SC-EACE process. Commercial interstitial-free steel sheets with width of 160 mm and thickness of 2 mm were processed repeatedly to various passes at room temperature using this method. The microstructural evolution was characterized using high-resolution electron backscatter diffraction (EBSD), and the mechanical properties were investigated by tensile testing. The EBSD images indicated that the fraction of high-angle boundaries (HABs) began to increase gradually after four passes; after six passes, elongated HAB structures with nearly submicron-scale average spacings were formed. The tensile testing results showed that strengthening was accompanied by a decrease in tensile ductility, but no significant anisotropy was observed. After 10 passes, a final HAB fraction of about 90% and an overall grain size of 0. 55 µm, yield strength of 638. 7 MPa, an ultimate tensile strength (UTS) of 710. 3 MPa, and a total elongation of 12. 0% were obtained.

Optimization of Temperature and Force Adaptation Algorithm in Hot Strip Mill

In the hot strip rolling control system, the temperature distribution and deformation resistance are the main parameters affecting prediction of rolling force. In order to improve the model prediction precision, an optimization algorithm based on objective function was put forward, in which the penalty function index was adopted. During the adaptation process, the temperature distribution and deformation resistance were taken as the optimized parameters, and the Nelder-Mead simplex algorithm was used to search the optimal solution of the objective function. Furthermore, the temperature adaptation and force adaptation were solved simultaneously. Application results show that the method can improve the accuracy of the rolling force model obviously, and it can meet the demand of the industrial production and has a good application prospect.

Calculation Method of Optimal Speed Profile for Hot Plate During Controlled Cooling Process

The healthy and rapid development of the controlled cooling technology was hampered by the uneven cooling phenomenon. During the process of hot plate production, the homogeneous cooling along the length direction of plate was constrained by lots of factors. And because the speed was a flexible control parameter, the calculation method of optimal speed profile was developed based on the measured start cooling temperature and its matrix equation was solved by the Cholesky decomposition method. The optimal speed profile was used in online control system. As a result, the temperature distribution along the plate length direction was relatively uniform, and 95% of measured final cooling temperature difference from the target temperature; 700 °C was controlled within +20 °C.

Cooling Efficiency of Laminar Cooling System for Plate Mill

Heat transfer was researched from a perspective of the industry application. On the basis of the first law of thermodynamics, the cooling efficiency was deduced from the change of enthalpy inside hot plate. The relationship between the cooling efficiency and its influencing parameters was regressed from plenty of data collected from the worksite and discussed in detail. The temperature profiles resulting from the online model and the model modified by regressed formulas were presented and compared. The results indicated that the control accuracy of the modified model was increased obviously.