Control system for papermaking machine headbox

Claim 1

An apparatus for controlling a paper machine headbox comprising: four sensors for directly measuring respective parameters of a paper making process and the disturbance to said parameters caused by operation of said machine, said sensors respectively directly measuring the pulp concentration in the headbox, the pulp level in the headbox, the total pressure in the headbox and a slice opening of the headbox; at least three actuators having inputs for controlling respective operative devices which affect said measured parameters of the process; a multivariable control system for receiving output signals from said four sensors and set point values for said measured parameters and supplying control signals to said at least three actuators, said control system comprising: first means providing a model of said process, said first means receiving setting signals which are applied to said at least three actuators and supplying first parameter output signals representing the interrelationship of said measured parameters with respect to actuator settings as determined by said process model; second means in parallel with said first means and providing a measurable disturbance model relating to said process, said second means receiving measured disturbance signals and supplying first parameter disturbance signals representing the interrelationship of parameter disturbances with respect to measured disturbances as determined by said disturbance model; third means providing a regulation reference model relating to said process, said third means being responsive to output signals from said sensors and said first and second means and providing output signals for eliminating said measured disturbances as determined by said regulation reference model; and, fourth means providing a tracking reference model relating to said process, said fourth means receiving set point values for said measured parameters and providing therefrom output signals representing desired values of said measured parameters of said process as determined by said tracking reference model; said control system providing individual control signals to said actuators in response to said sensor signals and the output signals of said first, second, third and fourth means for controlling at least one parameter of said process in direct response to a variation in said parameter from a disturbance, set point change, or both, by altering the inputs to said actuators, while minimizing the effects on the remainings parameters of said process.

Claim 2

An apparatus for controlling a paper machine headbox comprising: four sensors for directly measuring respective parameters of a paper making process and the disturbance to said parameters caused by operation of said machine, said sensors respectively directly measuring the pulp concentration in the headbox, the pulp level in the headbox, the total pressure in the headbox and a slice opening of the headbox; at least three actuators having inputs for controlling respective operative devices which affect said measured parameters of the process; a multivariable control system for receiving output signals from said four sensors and set point values for said measured parameters and supplying control signals to said at least three actuators, said control system comprising: first means providing a model of said process, said first means receiving setting signals which are applied to said at least three actuators and supplying first parameter output signals representing the interrelationship of said measured parameters with respect to actuator settings as determined by said process model; second means in parallel with said first means and providing a measurable disturbance model relating to said process, said second means receiving measured disturbance signals and supplying first parameter disturbance signals representing the interrelationship of parameter disturbances with respect to measured disturbances as determined by said disturbance model; third means providing a regulation reference model relating to said process, said third means being responsive to output signals from said sensors and said first and second means and providing output signals for eliminating said measured disturbances as determined by said regulation reference model; and, fourth means providing a tracking reference model relating to said process, said fourth means receiving set point values for said measured parameters and providing therefrom output signals representing desired values of said measured parameters of said process as determined by said tracking reference model; said control system providing individual control signals to said actuators in response to said sensor signals and the output signals of said first, second, third and fourth means for controlling at least one parameter of said process in direct response to a variation in said parameter from a disturbance, set point change, or both, by altering the inputs to said actuators, while minimizing the effects on the remainings parameters of said process.

Claim 6

An apparatus according to any of claims 1, 2, 3 or 4, wherein four actuators are provided which respectively act on an inlet stock valve in a pulp supply path of said headbox, on a pulp supply pump in said supply path, on a valve for the admission of air above the pulp level in said headbox and on a slice control of the outlet of said headbox.

Claim 7

An apparatus according to any of claims 1, 2, 3 or 4, wherein one of said parameters is controlled independently of said multivariable control system and a measurement signal of said one parameter is introduced into said multivariable control system as a measurable disturbance.