Patent Document ID: 5488561
Application ID: 08398598
Patent Flag: 1

Claim One:
1. In a process wherein input feed having at least one fluctuating parameter is processed to yield an output feed, and wherein at least one controlled variable in the output feed varies in response to changes in the setpoint of at least one manipulated variable, a method for varying the manipulated variable setpoint to achieve an independently variable target level of the controlled variable, said method comprising the steps of: (a) polling and collecting a plurality of process parameters affecting the controlled variable and affected by the manipulated variable; (b) in response to the process parameters collected in step (a) and to the present value of the manipulated variable setpoint, determining the difference between said present value and an optimal value for the manipulated variable setpoint for achieving the target level of the controlled variable; (c) in response to process parameters collected in step (a) and to the difference determined in step (b), predicting the level of the controlled variable that would result from applying said optimal manipulated setpoint value to the process; (d) obtaining the present level of the controlled variable; (e) comparing said predicted result from step (c) with said present level obtained in step (d) to provide a feedback signal; (f) in response to said feedback signal and to the present value of the manipulated variable setpoint, modifying said difference determined in step (b) so that said optimal manipulated variable setpoint value more closely achieves the target level of the controlled variable; and (g) applying a signal representing the modified optimal setpoint value derived in step (f) to control the manipulated variable setpoint in the process and thereby control the controlled variable in said output feed; wherein steps (a) through (g) constitute an optimization cycle regularly repeated at a predetermined frequency; wherein step (d) includes the steps of: (d.1) directly measuring the actual present level of the controlled variable; and (d.2) inferring the present level of the controlled variable from at least one related process parameter collected in step (a); and wherein step (e) comprises comparing said predetermined result from step (c) with both the measured actual level obtained in step (d.1) and the level inferred in step (d.2) to provide said feedback signal; and further comprising the steps of: (h) storing, for each optimization cycle, the difference determined in step (b) and the actual level of the controlled variable measured in step (d.1); and (i) during every Mth optimization cycle, incorporating a tuning factor into said feedback signal to reduce the magnitude of the modification required in the difference determined in step (b) to achieve the target value of the controlled variable, wherein said tuning factor is derived from trends in said difference and said actual level stored in step (h); wherein M is a predetermined multiple of optimization cycles of such magnitude as to encompass a plurality of hours; wherein step (i) includes modifying said feedback signal by modifying the entirety of said polynomial by a common scaling factor; and further comprising the step of: (j) after every L optimization cycles, recalibrating the process to accommodate variations in process performance resulting from changes, deletions or additions of process equipment, the variations in performance being observed from the differences and levels stored in step (h); wherein L is a multiple of optimization cycles encompassing a time frame on the order of a few days.