An improved valve stiction simulation model based on ISA standard tests

The Choudhury valve model is a widely adopted data-driven model to study the behaviour of valve stiction. A recent study (Garcia, 2008) revealed that valve stiction simulation based on Choudhury’s simulation model (Choudhury, Thornhill, & Shah, 2005) fails to pass eight out of fifteen Industry Standard Architecture (ISA) standard tests (ISA, 2000, ISA, 2006) for real control valves. In this study, the ISA testing results are further elaborated for this model. It is found that three minor deficiencies lead to the discrepancies between the Choudhury Model outputs and the expected ones when (i) the valve input signal changes the direction of travel, (ii) the initial stem position does not stay on the working curves l₁ and l₂, and (iii) the valve input signal changes in a ramp–pause–ramp manner. To address the above deficiencies, an improved version of the Choudhury Model, termed as XCH Model, is proposed. Assessments along with the ISA standards presented by Garcia (2008) demonstrate the proposed XCH Model passes all the ISA standard tests and thus provides a more realistic simulation of a real industrial valve being able to exhibit stiction behaviour.