Control

Machine direction (MD) thickness and cross-machine direction (CD) thickness are controlled by the control unit. Based on the type of film making machine (such as cast and bi-axially oriented) and response time, the appropriate control method can be selected from the following options: virtual zone sampled data PI control, finite settling model predictive control, and expert fuzzy control.

Other control methods are available: CD adaptive control continually monitors the process status during CD control to automatically recognize and adjust mappings between actuators and measurement points on profiles. By formulating rules based on the customers' control know-how, peaks can be aligned to achieve a flat roll shape

MD Control

This method utilizes MD to control the thickness of films and sheets. Either sampled data PI control or finite time settling response control can be selected. Up to four loops can be implemented for each measurement operator station.

Virtual Zone Sampled Data PI CD Control

Virtual zone profile control has already achieved satisfactory results in many processes. This generates profiles at the midpoint between real bolts as well as on these bolts to perform control calculation. This prevents the occurrence of profile peaks and troughs between the bolts, which often become a problem in conventional profile controls only intended for profiles on the bolts. (Yokogawa patents)

Expert Fuzzy CD Control

Expert fuzzy control based on fuzzy logic incorporates the manual bolt operation expertise of experienced machinery operators. This control method is effective with machines (mainly bi-axially oriented machines) where there is low repeatability of profile response to bolt manipulations, realizing stabler control than conventional control methods. Expert fuzzy control employs the concept of the virtual zone.

Finite Settling Model Predictive CD Control

Finite settling model predictive control applies the finite time settling response method to profile control. This predictive control employs a dead time internal model and a first-order lag system so that even machines with long lag times can settle down to target values within the shortest possible time. The control has a dramatic effect on machines with long lag times.

Automatic Mapping Control (CD Adaptive Control)

Mapping is the most important parameter of CD control; however, it varies depending on operational conditions such as stretch ratio and machine speed. For this reason, setting parameters for each grade and re-tuning have been required to maintain optimum control.

Always monitoring the process status during CD control, CD adaptive control automatically recognizes and adjusts mappings between actuators (such as heat bolts) and measurement points on profiles using a proprietary Yokogawa algorithm that combines the steepest descent method with a neural network.

Roll Shape Control

This incorporates rules that have been formulated based on the customers' know-how and applies it to CD control. By means of CD control, it improves roll shape by eliminating outstanding peaks.