Ziying Liu

Application and Research of New Monitor AGC in Hot Strip Mill

A Monitor AGC control system is applied to a hot strip mill in a steel plant, due to some irrationality gain factors and the hysteresis of the Monitor AGC control output, the strip thickness deviation is large. This paper designs a new type Monitor AGC that includes two control methods:Integral type Monitor AGC and Smiths method Monitor AGC, they are able to select alternately. The experimental results show that the effect of Integral type Monitor AGC and Smiths method Monitor AGC is obvious, and the accuracy of thickness control is obviously improved.

High-Precision Header Flux Control of Ultra-Fast Cooling in Hot Strip Mill By PI Controlle

A new header flux controller of an ultra-fast cooling (UFC) system was investigated during hot strip rolling. The UFC header flux was calibrated by changing the opening rate of the adjusting valve from 0% to 95% and, reversely, from 95% to 0%, in increments of 5%. The results showed that the header flux was rarely influenced by the changing direction of the adjusting valve. Based on the analysis of the flux adjusting, the definition of adjusting-efficiency (A-E) of flux was introduced and the corresponding equation was established. A Proportion-Integral (PI) controller, based on A-E, was employed to implement the closed-loop control of the header flux. The results from the on-site implementation indicated that the flux deviation between target and measured values was less than ±1.0m3/h.

The Application and Research of NI Controller on Cold-rolling Simulator

This cold-rolling simulator is mainly used for exploitation of new productions and research for new technique. The execution system of this cold-rolling simulator includes hydraulic drive system and electric drive system. The features, such as multivariable, nonlinear, real-time, and high-speed, set high requirements for the control system. The PXI system is a compact modular PC platform for test, measurement, and control system, which meets the specific needs of the cold-rolling simulator by adding an integrated trigger bus and reference clock for multiple-board synchronization, a star trigger bus for very precise timing, and local buses for side-band communication. This control system of the cold-rolling simulator is mainly composed of PXI system and S7 PLC.

Model to Calculate the Cooling Rate along the Strip Length Direction in Hot Strip Mill

The basic theory of cooling after rolling was introduced firstly. The cooling process of strip steel was summarized as three typical cases. On the basis of Time-Velocity-Distance (TVD) curve, the cooling time model in each case was calculated. By means of the measured finishing delivery temperature, coiling temperature and the Stefan-Boltzmann law, the temperature drop was calculated. Combining the cooling time with the temperature drop, the calculating model for cooling rate along the strip length direction was developed in hot strip mill. The achievement was applied to a hot strip plant successfully. With the help of the results of cooling rate, process parameters were set up and controlled accurately and conveniently.

Development of Step Cooling Control System After Rolling Based on Automatic Feedback Control in Hot Strip Mill

Combined with a hot strip mill line, the laminar and step cooling mathematical models for cooling after rolling were introduced. The mathematical models mainly include air cooling model, water cooling model, setup control model, feed forward control model and feedback control model. Due to the delay of the feedback control, the original system could not achieve high precision control of the coiling temperature. Based on the process requirements of rolling dual phase steel, a new step cooling control system based on SMITH automatic feedback control was developed, and the cooling path and the configuration of the spray were re-divided. The experimental application showed that the optimized system had a stable operation and high control precision, the control precision of MT and CT is about 95%, which had significantly improved the performance of the product and laid a foundation for the rolling of new steels.

Simulation model of PI controller for the header flux control of ultra-fast cooling in hot strip mill

Parameters optimization of the PI controller was investigated for the header flux control of Ultra-fast cooling. Taking the measured curve, Ultra-fast cooling (UFC) header flux under different open rate of valve, as the input parameters, a simulation model was developed. Based on the coupling control of proportion(P) and integration(I), the parameters with minimum root-mean-square-error of header flux was considered as the best. The simulation results showed that the optimal integration time was 600ms under industrial conditions. Furthermore, the correction equations for the P and I controller were established by the newly developed simulation model. The results from the on-site implementation indicated that the flux deviation between target and measured values was less than ±l.0m3/h during the constant operation of the UFC header, and the overshoot value was within 3.0m3/h of the apparent interference.

Development and Application of Self-learning Model for HSM

In recent years, based on maturity of AGC technology, the accuracy of Thickness Control has been improved greatly. The poor profile control is the major factor which restricts the dimensional accuracy. The mathematical model of plate shape-setup is the basis for realizing the process control of strip mill. Because the deviation of the mathematical model, the device and the parameter is inevitable during actual rolling, self-learning is an important mean to reduce the error of the set-up model. On a production line, the self-learning algorithm is not in line with actual production, which results in control chaos. To solve this problem, combined with the actual production process, a new self-learning algorithm has been developed, which considers operator revision, unstable error interference and actual parameters optimization. New algorithms has been applied, it has solved the phenomenon of self-learning disorder, improved the hit rate of profile greatly, and improved the quality of the production.