Research and Application of Dynamic Substitution Control of Actuators in Flatness Control of Cold Rolling Mill

At present, most of the multi-variable flatness control systems of cold rolling mills are developed based on global optimisation methods. However, the global optimisation methods always occupy a large amount of the controller resource, leading to a reduced control efficiency and real-time performance. In order to improve the efficiency of multi-variable flatness control, a new control method, based on the relay optimisation, has been proposed. First of all, the multivariable optimisation model of flatness control is converted into a series of univariable optimisation models in the relay mode. Then the optimal adjustments of various flatness actuators will be obtained in cyclic optimisation processes. Moreover, the structure of flatness control system and the time delay compensation strategy have been designed in accordance with the proposed method. It is found that the proposed control method is efficient and effective for the multi-variable flatness control process by means of numerical experiments and applications.

Section: The Design Of Optimisation Model For Multi-variable Flatness...mentioning

confidence: 99%

Flatness control of cold rolled strip based on relay optimisation

Wang

Zhang

Sun

et al. 2016

Section: Determination Of Actuator Efficiency Factorsmentioning

confidence: 99%

“…It can be used to describe any performance forms of flatness actuators without further pattern recognition and decoupling calculation of flatness deviation. 11,12 The actuator efficiency is the resulting amount of flatness change under unit volume regulation of individual flatness actuator, 13 and equation (2) gives the expression of the actuator efficiency for flatness control: where Eff is the matrix of actuator efficiency factor for flatness control, and Eff∈ R m × n , Δ U is the adjustment value vector of flatness actuators, and Δ U ∈ R n , Δ Y is the vector of the resulting flatness change value vector, and Δ Y ∈ R m .…”

Section: The Optimisation Problem In Multi-variable Flatness Controlmentioning

confidence: 99%

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

Wang

Qiao

Zhang

et al. 2016

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.

“…Zhang et al 14 introduced the rate of change of quadratic and quartic crowns in order to analyse the performance of each flatness control device of a CVC mill. In addition, the matrix of actuator efficiency factor has been shown to be a useful alternative and it was used by Wang et al 15 to find appropriate actuators for dynamic substitution control. Most of these methods have focused on the relative changes in crowns.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the matrix of actuator efficiency factor has been shown to be a useful alternative and it was used by Wang et al . 15 to find appropriate actuators for dynamic substitution control. Most of these methods have focused on the relative changes in crowns.…”

Section: Introductionmentioning

confidence: 99%

Development and application of a new method for evaluating shape controllability of rolling mills for flat products

Niu

Peng

2016

A new method is developed for quantifying the shape controllability of rolling mills for flat products. The method enables one to acquire a comprehensive and accurate assessment of shape control performance in such a way that both the adjusting range and the ability to bear undesirable rolling force fluctuations can be efficiently articulated, understood and studied. A concise discussion concluding the formulation of the evaluation system is offered regarding the general applicability of it. To demonstrate the feasibility of our approach, an example application is presented to the adjustment characteristics analysis of a six-high mill for its three fast acting actuators. Significant differences are found in the effects of work stability changes on the stand's capability to counter quadratic and quartic terms of flatness deviations. The underlying factors which are likely to be responsible for such differences and an unfavourable condition that may arise in actual production are also discussed.