Patent ID: 7797082

Claim:
An apparatus, comprising: at least one memory operable to store operating data associated with a valve; and at least one processor operable to: identify whether the valve is suffering from stiction using at least part of the operating data; and adjust a control signal produced by a controller for the valve in order to at least partially compensate for the stiction suffered by the valve; wherein the at least one processor is operable to adjust the control signal by (i) adjusting the control signal to cause the valve to move into a steady-state position and (ii) adjusting the control signal to cause the valve to remain in the steady-state position; wherein the at least one processor is operable to adjust the control signal to cause the valve to move into the steady-state position by (i) generating one or more first compensating signals for adjusting the control signal to cause the valve to move from a starting position into one or more new positions, (ii) predicting a next value of the control signal using a model of the controller, and (iii) generating, based on the predicted next value of the control signal, a second compensating signal for adjusting the control signal to cause the valve to move from a last of the one or more new positions into the steady-state position; wherein the at least one processor is operable to identify whether the valve is suffering from stiction by (i) determining a qualitative stiction severity measure by performing qualitative pattern recognition and (ii) determining a quantitative stiction severity measure by performing a model identification procedure; and wherein the at least one processor is operable to determine the qualitative stiction severity measure by: removing a non-constant mean from the at least part of the operating data to produce a mean-shifted signal; computing an area associated with the mean-shifted signal and normalizing the area to produce an area curve; and finding one or more points at which slope changes occur in the area curve to identify one or more zero-crossings.