Process control methods and apparatus
AssigneeYokogawa Electric Corporation
InventorTakashi Sasaki
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Abstract
The present invention provides a method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting the controlled/manipulated variable to the process, wherein conditions for the process variable to settle within a finite length of time are determined from the final-value theorem, the transfer function of the controller is derived from the conditions, and the value of or change in the controlled/manipulated variable with which to control the process is calculated using the transfer function. With this control method and apparatus for the method, it is possible to allow even a process with a long dead time and a large time constant to settle within a short length of time.
Claims11
A process control method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, comprising the steps of:
- determining conditions for said process variable to settle within a finite length of time from the final-value theorem;
- concluding the transfer function of said controller from said conditions;
- and
- calculating the value of or change in said controlled/manipulated variable with which to control said process, using said transfer function.
A process control method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, wherein the value of said controlled/manipulated variable in a current control period is calculated from deviations in said current control period and earlier control periods and the values of said controlled/manipulated variable in said earlier control periods.
A process control method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, wherein a change in said controlled/manipulated variable in a current control period is calculated from deviations in said current control period and earlier control periods and changes in said controlled/manipulated variable in said earlier control periods.
A process control method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, comprising the steps of:
- determining conditions for said process variable to settle within a finite length of time from the final-value theorem;
- concluding the transfer function of said controller from said conditions;
- calculating a change in said controlled/manipulated variable with which to control said process, using said transfer function;
- and
- correcting a deviation variable to be input to said transfer function, by using a value related to the amount of change in said controlled/manipulated variable that could not be output in the previous and earlier control periods.
A process control method for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, comprising the steps of:
- calculating a change in said controlled/manipulated variable in a current control period from deviations in said current control period and earlier control periods and a value related to changes in said controlled/manipulated variable in said earlier control periods;
- and
- correcting said deviation by using the amount of change in said controlled/manipulated variable that could not be output in the previous and earlier control periods.
A process control apparatus for controlling a process by inputting a deviation between setpoint and process variables to a controller to calculate a controlled/manipulated variable, and then inputting said controlled/manipulated variable to said process, comprising:
- finite-time settling means for determining conditions for said process variable to settle within a finite length of time from the final-value theorem;
- transfer function conclusion means for concluding the transfer function of said controller from said conditions;
- and
- computation means for calculating the value of or change in said controlled/manipulated variable with which to control said process, using said transfer function.
Dependencies are inferred from the claim text.