Patent ID: 7216057

Claim:
A method for analysing the performance of a control circuit in an industrial process, comprising: collecting from an operating control circuit data illustrating the operation of the control circuit; calculating two or more control circuit performance indices on the basis of the collected data; calculating for each calculated or scaled performance index its degree of membership in two or more membership degree classes; forming predetermined combinations of the membership classes of the performance indices; checking whether the control circuit was in an externally controlled operating mode, instead of an automated control mode, during the data collection period, wherein if the control circuit was in the externally controlled mode, the control circuit state is not interpreted by means of said performance indices, and if the control circuit was not in the externally controlled mode during the data collection period, i) evaluating the correlation of each combination with a corresponding reference state by means of the calculated membership degrees, and ii) interpreting the reference state that provides the best correlation with one of the combinations to represent the state of the control cicuit; and presenting to the user via a user interface the interpreted state of the control circuit, or a proportionate presentation illustrating interpreted states of the control circuit over a longer period of time.