US4714988A — Feedforward feedback control having predictive di…

Claim 1

Independent Claim 111 words

A process control system which adapts itself optimally to variations in disturbance, comprising: feedback control means for outputting a feedback control signal thatis computed by comparing a set value and a process value; feedforward control means for detecting a disturbance and for outputting a disturbance compensation signal to compensate for the disturbance based on a feedforward control model; and gain adaptive means for comparing said disturbance compensation signal and a manipulated signal, which is a function of said feedback control signal and said disturbance compensation signal, and for correcting the gain of said feedforward control model so that the difference between the disturbance compensation signal and the manipulated signal is reduced.

Claim 2

Dependent Claim 111 words

A process control system which adapts itself optimally to variations in disturbance, comprising: feedback control means for outputting a feedback control signal thatis computed by comparing a set value and a process value; feedforward control means for detecting a disturbance and for outputting a disturbance compensation signal to compensate for the disturbance based on a feedforward control model; and gain adaptive means for comparing said disturbance compensation signal and a manipulated signal, which is a function of said feedback control signal and said disturbance compensation signal, and for correcting the gain of said feedforward control model so that the difference between the disturbance compensation signal and the manipulated signal is reduced.

Claim 3

Dependent Claim 35 words

A system as claimed in claim 1, in which the gain adaptive means corrects the gain of the feedforward control model so that the feedback control signal outputted from the feedback control means is reduced.

Claim 4

Dependent Claim 21 words

A system as claimed in claim 1, in which the gain adaptive means corrects periodically the gain of the feedforward control.

Claim 5

Dependent Claim 43 words

A system as claimed in claim 1, in which the gain adaptive means judges the magnitude of the gain of the feedback control signal or the manipulated signal, and corrects the gain of the feedforward control model when it exceeds a prescribed level.

Claim 6

Dependent Claim 66 words

A system as claimed in claim 4, in which the gain adaptive means comprises a correction unit with a transfer function as shown by the following equation: ##EQU16## wherein K n-1 is the gain of the feedforward model for the preceding time, Mn is the manipulated quantity for the present time, Bn is the feedforward quantity for the present time, and k is a correction coefficient.

Claim 7

Dependent Claim 22 words

A system as claimed in claim 5, in which the correction coefficient k in the gain correction unit is equal to unity.

Claim 8

Dependent Claim 22 words

A system as claimed in claim 5, in which the correction coefficient k in the gain correction unit satisfies the relation 0<k<1.

Claim 9

Dependent Claim 53 words

A system as claimed in Claim 1, in which the feedforward control model comprises a gain memory for storing the gain correction signal from the gain adaptive means and an operational means for receiving the correction signal from the gain memory and the disturbance signal to compute and output the disturbance compensation signal.

Claim 10

Dependent Claim 80 words

A system as claimed in claim 8, further comprising a gain adaptive mechanism for permitting the supply of the gain correction signal to the gain memory when detecting a state in which the process is steady, the control is set, and the difference between the disturbance compensation signal and manipulated quantity exceeds a prescribed value and continues for a predetermined time length, and for controlling the generation of the function of the disturbance compensation signal and the feedback control signal.

Claim 11

Dependent Claim 44 words

A system as claimed in claim 9, further comprising a dynamic characteristic compensation circuit for receiving the disturbance compensation signal and determining a dynamic compensation signal, said dynamic compensation signal being added to the manipulated signal, in order to compensate for the dynamic characteristics.

Claim 12

Dependent Claim 121 words

A system as claimed in claim 4, in which the gain adaptive means comprises a sample value control unit, a signal correction system for correcting the disturbance compensation signal and the manipulated signal which is output to the process so that the disturbance compensation signal and the manipulated signal are equal to each other, and a correction influence compensation system for compensating the disturbance compensation signal which is corrected by the signal correction system so as to suppress adverse effect due to correction, both of these systems executing the automatic correction and compensation operation, based on the correction signal from the sample value control unit, so as to minimize the degree of contribution of the feedback control to the feedback/feedforward control.

Claim 13

Dependent Claim 93 words

A system as claimed in claim 11, in which the signal correction system comprises a first multiplier for multiplying the correction signal from the sample control unit by the disturbance compensation signal from the feedforward control model, and the correction influence compensation system comprises a second multiplier for multiplying the disturbance compensation signal from the feedforward control model by the correction signal from the sample value control unit and a compensator for subtracting the influence compensation signal supplied from the second multiplier from the corrected disturbance compensation signal supplied from the first multiplier.

Claim 14

Independent Claim 98 words

A method of process control comprising in combination a feedback control in which a manipulated variable is determined in accordance with a deviation of a controlled variable with reference to a target value and a feed-forward control in which a disturbance is detected and a disturbance compensation is determined and used in determining the manipulated variable to counteract the effect of the disturbance, said method comprising the step of: adjusting, when the process is in a steady state, said disturbance compensation in such a manner that the difference between the disturbance compensation and the manipulated variable is reduced.

Claim 15

Independent Claim 98 words

A method of process control comprising in combination a feedback control in which a manipulated variable is determined in accordance with a deviation of a controlled variable with reference to a target value and a feed-forward control in which a disturbance is detected and a disturbance compensation is determined and used in determining the manipulated variable to counteract the effect of the disturbance, said method comprising the step of: adjusting, when the process is in a steady state, said disturbance compensation in such a manner that the difference between the disturbance compensation and the manipulated variable is reduced.

Claim 16

Dependent Claim 41 words

A method as claimed in claim 13, in which said step of adjusting comprises: determining a coefficient in accordance with the disturbance compensation and the manipulated variable, and multiplying the detected disturbance by said coefficient to produce an adjusted disturbance compensation.

Claim 17

Dependent Claim 33 words

A method as claimed in claim 13, in which said step of adjusting comprises: determining the difference between the compensation component and the manipulated variable, and integrating said difference to produce said coefficient.

Claim 18

Dependent Claim 118 words

A method as claimed in claim 13, in which said deviation is applied to a velocity-type controller, and a static compensation component and a dynamic compensation component of said disturbance compensation are determined in accordance with the detected disturbance, and said method further comprises the steps of: determining, in accordance with the detected disturbance, a static compensation component and a dynamic compensation component of the disturbance compensation, converting the static compensation component to a velocity type signal, adding the converted static compensation component to the output of the controller to obtain a first sum, converting the first sum to a position type signal, adding the dynamic compensation component to the converted first sum to obtain the manipulated variable.

Claim 19

Dependent Claim 126 words

A process control system comprising in combination a feed-back control system determining a manipulated variable in accordance with a deviation of the controlled variable with reference to a target value, and a feed-forward control system having means for detecting a disturbance and determining, in accordance with the detected disturbance, a disturbance compensation to be used in determining the manipulated variable to counteract the effect of the disturbance, said process control system comprising: disturbance compensation determining means determiniing, in accordance with the detected disturbance, the disturbance compensation, and judging means for judging whether or not the control is in a steady state, said disturbance compensation determining means modifying a factor for determining the disturbance compensation to reduce the difference between the disturbance compensation and the manipulated variable.

Claim 20

Dependent Claim 126 words

A process control system comprising in combination a feed-back control system determining a manipulated variable in accordance with a deviation of the controlled variable with reference to a target value, and a feed-forward control system having means for detecting a disturbance and determining, in accordance with the detected disturbance, a disturbance compensation to be used in determining the manipulated variable to counteract the effect of the disturbance, said process control system comprising: disturbance compensation determining means determiniing, in accordance with the detected disturbance, the disturbance compensation, and judging means for judging whether or not the control is in a steady state, said disturbance compensation determining means modifying a factor for determining the disturbance compensation to reduce the difference between the disturbance compensation and the manipulated variable.

Claim 21

Dependent Claim 48 words

A system as claimed in claim 17, in which said disturbance compensation determining means comprises a multiplier and means for determining a coefficient in accordance with the disturbance compensation and the manipulated variable, said multiplier multiplying the detected disturbance by said coefficient to produce an adjusted disturbance compensation.

Claim 22

Dependent Claim 41 words

A system as claimed in claim 18, in which said means for determining a coefficient comprises: subtracting means for determining the difference between the compensation component and the manipulated variable, and integrating means for integrating said difference to produce said coefficient.

Claim 23

Dependent Claim 139 words

A process control system as claimed in claim 17, in which said feed-back control system comprises a velocity type controller, said disturbance compensation means determines, in accordance with the detected disturbance, a static compensation component and a dynamic compensation component of the disturbance compensation, and said process control system further comprises: position type to velocity type converting means for converting the static compensation component into a velocity type signal, first adding means for adding the output of the position type to velocity type converting means and the output of the controller to obtain a first sum, velocity type to position type converting means for converting the first sum into a position type signal, and second adding means for adding the dynamic compensation component and the output of the velocity type to position type converter to obtain the manipulated variable.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-12-21	1991-06-22	1991-12-22	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-12-21	1995-06-22	1995-12-22	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-12-21	1999-06-22	1999-12-22	$7700.00	Window Closed / Lapsed

Feedforward feedback control having predictive disturbance compensation

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