Method and system for process control with complex inference mechanism using qualitative and quantitative reasoning

A method of performing a process control in accordance with a plurality of controlled objects with a transition of a process being predicted, comprising the steps of:

• using input process information and an assumed manipulation quantity for arithmetically operating on predicted values of control quantities for the plurality of controlled objects a predetermined period of time after a current control timing by using means for performing a quantitative arithmetic operation which simulates the process in a linear relation and means for performing a qualitative arithmetic operation which simulates the process in a fuzzy rule relation, respectively;
• determining whether a process behavior at the current control timing is linear based on an evaluation rule which evaluates the linearity of the process behavior;
• selecting one of the predicted values obtained by the quantitative arithmetic operation means and obtained by said qualitative arithmetic operation means based on a result of said determining step;
• determining the grade of satisfaction in which said plurality of controlled objects are as a whole satisfied with respective predicted values selected by said selecting step;
• and
• if said determined satisfaction grade meets a predetermined reference, controlling the process using the assumed manipulation quantities.

A process control system, including a computer system, for controlling a manipulation quantity of a control effector in accordance with a target quantity of a controlled object with a transition of a process being predicted, comprising:

• quantitative arithmetic operation means for simulating a process in a linear relation to predict a control quantity of the controlled object a predetermined period of time after inputting of process information;
• qualitative arithmetic operation means for simulating a process in a fuzzy rule relation to predict a control quantity of the controlled object a predetermined period of time after inputting of process information;
• process behavior inference means, having a set of production rules which evaluate linearity of non-linearity of a process behavior based on empirical knowledge, for determining whether the process behavior is linear or non-linear from the process information at a current timing;
• manipulation quantity output means, responsive to a determination by said process behavior inference means, for selecting one of said quantitative arithmetic operation means and said qualitative arithmetic operation means and for outputting a determined manipulation quantity, based on a difference between said predicted value and said target quantity;
• and
• control means for controlling the process on the basis of said determined manipulation quantity.

A process control system, including a computer system, for controlling manipulation quantities of a plurality of control effectors for a process in accordance with a plurality of controlled objects while a transition of the process is being predicted, comprising:

• manipulation quantity candidate generation means for generating candidates on combination of predetermined manipulation quantities which are changeable from a current combination of manipulation quantities;
• prediction means including quantitative arithmetic operation means for simulating the process in a linear relation and qualitative arithmetic operation means for simulating the process in a fuzzy rile relation, and for parallelly arithmetically operating on a control quantity of each of the controlled objects a predetermined period of time after a current time based on input process information and candidates on the combination of manipulation quantities;
• process behavior inference means, including a set of production rules based on empirical knowledge evaluating the degree of linearity or the degree of non-linearity of the process behavior, for determining whether the process behavior is linear based on predetermined process information at a relevant timing;
• manipulation quantity output means for selecting predicted values of one of said quantitative arithmetic operation means and said qualitative arithmetic operation means in accordance with a determination result of said process behavior inference means, and outputting said candidates on the combination of manipulation quantities to a plurality of corresponding control effectors when the degree of satisfaction obtained by the selected predicted values to thereby satisfy the plurality of controlled objects collectively meets a predetermined reference;
• and
• means for controlling the process on the basis of said manipulation quantities.