Model predictive controller for coordinated cross direction and machine direction control

Abstract

A process for coordinated control of machine direction MD and cross direction CD actuators in a sheetmaking machine for manufacturing a sheet of material is disclosed. The process involves measuring a plurality of sheet properties at regular intervals to collect sheet measurement data. The sheet measurement data is manipulated to establish a plurality of sheet property measurement arrays, which are then mapped to a common resolution. The common resolution sheet property measurement arrays are concatenated into one larger one-dimensional common resolution measurement array. The common resolution measurement array and an array of past changes in actuator set point are used as inputs to a paper machine process model state observer to generate the estimated current internal state of the sheet manufacturing process. A plurality of future sheet property target arrays are concatenated into one target array. The array of the estimated current internal state of the web manufacturing process and the paper machine process model are employed to generate an array of future predictions of sheet properties. The array of future predictions of sheet properties, the target array, object function weights, the last actuator set points, and hard constraints are inputted into an object function which is solved to yield optimal changes in the actuator set points for coordinated MD and CD control of the sheet making process.

Description

technical field [0001] The present invention relates to the control of the papermaking process and more particularly to a method for coordinating the operation of machine direction and transverse actuators in a papermaking machine. Background technique [0002] Control of paper properties in a paper machine involves bringing the paper properties as close as possible to target values. There are two different sets of actuators for controlling the properties of the paper. First, there are machine direction (MD) actuators which only affect the cross direction (CD) average of the paper properties. Each MD actuator can have a different dynamic response to paper properties. Second, have CD actuators that line up the paper in the CD direction. Each CD actuator array can affect the average of the paper properties as well as the CD shape. CD actuators can have different dynamic responses and different spatial responses to paper properties. The problem with overall control of pape...

AI Technical Summary

Problems solved by technology

First, only the MD actuator is used to control the CD average without the effect of the CD actuator on the CD average of the paper properties

Second, the CD actuators arrayed on this paper are only used to control the change in CD around the average value of the paper properties

Images