Dual mode process control with continuous feedback during coarse mode

Claim 2

In a process having a manipulated variable and a controlled variable, said manipulated variable effecting control of said controlled variable, a method of coarse mode control changing said controlled variable to a new condition in response to a command signal designating said new condition, comprising the steps of: providing a control signal in response to said command signal for the operation of said manipulated variable in a predetermined manner to cause said change of said controlled variable; providing a feasible response signal representing the predicted response of said controlled variable to said control signal operation of said manipulated variable; measuring the actual response of said controlled variable, providing a measurement signal representing said actual response; comparing said feasible response signal to said measurement signal to provide an error signal indicating both the direction and magnitude of the difference therebetween; and summing algebraically said control signal and said error signal for controlling said manipulated variable in accordance therewith.

Claim 3

The method of claim 1 for additionally maintaining fine mode control of said controlled variable at said new condition, comprising: the additional step of, upon said feasible response signal reaching the value designated by said command signal on a steady state basis, maintaining said feasible response signal at said value designated by said command signal, whereby said measuring and comparing steps provide said error signal; and said summing step comprises controlling said manipulated variable in accordance with said error signal.

Claim 4

The method of claim 2, wherein said step of providing said control signal in response to said command signal includes arranging said control signal to operate said manipulated variable to cause said coarse mode change of said controlled variable at the optimum rate for said process.

Claim 5

The method of claim 3, wherein said manipulated variable may be varied only within preset limits; and wherein said step of providing said control signal includes arranging said control signal for operating said manipulated variable near one of said preset limits for the time required to change said controlled variable at the optimum rate for said process.

Claim 6

The method of claim 1 wherein said step of providing said control signal in response to said command signal includes the steps of: providing a manipulated variable signal representing the condition of said manipulated variable; comparing said manipulated variable signal to signals representing the limits of a predetermined tolerance range surrounding the initial steady state value of said manipulated variable to provide a signal indication of the result of said comparison indicating whether said manipulated variable condition is within or without said limits; and responding to said signal indication indicating said manipulated variable is within said limits to provide said control signal arranged to operate said manipulated variable to cause said change of said controlled variable at the optimum rate for said process, and responding to said signal indication indicating said manipulated variable is without said limits to provide said control signal arranged to operate said manipulated variable to cause said change of said controlled variable at a non-optimum rate.

Claim 7

The method of claim 5 for additionally maintaining fine mode control of said controlled variable at said new condition, comprising: the additional step of, upon said feasible response signal reaching the value designated by said command signal on a steady state basis, maintaining said feasible response signal at said value designated by said command signal, whereby said measuring and comparing steps provide said error signal; and Said summing step comprises controlling said manipualted variable in accordance with said error signal.

Claim 8

In a process control system for a process, said system having an input for receiving command signals, actuator means for controlling a manipulated variable of said process, and measuring means for supplying a measurement signal measuring a controlled variable of said process, said manipulated variable effecting control of said controlled variable, there being a predetermined model of said process representing the relationship between said manipulated variable and said controlled variable, the improvement thereto for coarse mode control of said process to change said controlled variable to a new condition in response to a command signal at said input designating said new condition, comprising: control and feasible response means responsive to said command signal for supplying a control signal for operating said actuator means to control said manipulated variable in a predetermined manner to cause said change of said controlled variable, and for supplying a feasible response signal in accordance with said predetermined model of said process, said feasible response signal representing the predicted response of said controlled variable to said control signal operation of said manipulated variable; comparison means comparing said feasible response signal to said measurement signal to provide an error signal indicating both the direction and magnitude of the difference therebetween; and summing means for algebraically summing said control signal and said error signal to operate said actuator means in accordance therewith.

Claim 9

In a process control system for a process, said system having an input for receiving command signals, actuator means for controlling a manipulated variable of said process, and measuring means for supplying a measurement signal measuring a controlled variable of said process, said manipulated variable effecting control of said controlled variable, there being a predetermined model of said process representing the relationship between said manipulated variable and said controlled variable, the improvement thereto for coarse mode control of said process to change said controlled variable to a new condition in response to a command signal at said input designating said new condition, comprising: control and feasible response means responsive to said command signal for supplying a control signal for operating said actuator means to control said manipulated variable in a predetermined manner to cause said change of said controlled variable, and for supplying a feasible response signal in accordance with said predetermined model of said process, said feasible response signal representing the predicted response of said controlled variable to said control signal operation of said manipulated variable; comparison means comparing said feasible response signal to said measurement signal to provide an error signal indicating both the direction and magnitude of the difference therebetween; and summing means for algebraically summing said control signal and said error signal to operate said actuator means in accordance therewith.

Claim 10

The process control system of claim 7 for additionally maintaining fine mode control of said controlled variable at said new condition, wherein said control and feasible response means additionally maintains said feasible response signal at the value designated by said command signal.

Claim 11

The process control system of claim 8 wherein said actuator means may be operated only within preset limits; and wherein said control and feasible response means supplies said control signal for operating said actuator means near one of said preset limits for the time required to change said controlled variable at the optimum rate for said process.

Claim 12

The process control system of claim 9 additionally including: means for supplying a manipulated variable signal representing the condition of said actuator means; and said control and feasible response means comprises: means responsive to the occurrency of said command signal for determining from said measurement signal the corresponding initial steady state value of the manipulated variable; means responsive to said determined initial steady state value of the manipulated variable and to signals representing the limits of a predetermined tolerance range for comparing said manipulated variable signal to said limits representing said tolerance range surrounding said initial steady state value to provide a signal indication of whether said actuator means condition is within or without said limits of said range; control means responsive to said signal indication indicating said actuator means condition is within said limits to provide said control signal for operating said actuator means to control said manipulated variable to cause said optimum rate for said process, and responsive to said signal indication indicating said actuator means condition is without said limits to provide said control signal for operating said actuator means to control said manipulated variable to cause said change of said controlled variable at a non-optimum rate; and feasible response means for supplying a feasible response signal in accordance with said predetermined model of said process, said feasible response signal representing the predicted response of said controlled variable to said control of said manipulated variable by said actuator in accordance with said provided contRol signal.