System identification applied to stiction quantification in industrial control loops: A comparative study

Abstract

A comparative study of different models and identification techniques applied to the quantification of valve stiction in industrial control loops is presented in this paper, with the objective of taking into account for the presence of external disturbances. A Hammerstein system is used to model the controlled process (linear block) and the sticky valve (nonlinear block): five different candidates for the linear block and two different candidates for the nonlinear block are evaluated and compared. Two of the five linear models include a nonstationary disturbance term that is estimated along with the input-to-output model, and these extended models are meant to cope with situations in which significant nonzero mean disturbances affect the collected data. The comparison of the different models and identification methods is carried out thoroughly in three steps: simulation, application to pilot plant data and application to industrial loops. In the first two cases (simulation and pilot plant) the specific source of fault (stiction with/without external disturbances) is known and hence a validation of each candidate can be carried out more easily. Nonetheless, each fault case considered in the previous two steps has been found in the application to a large number of datasets collected from industrial loops, and hence the merits and limitations of each candidate have been confirmed. As a result of this study, extended models are proved to be effective when large, time varying disturbances affect the system, whereas conventional (stationary) noise models are more effective elsewhere

Is Fault Detection and Diagnosis in Pneumatic Actuator A Topic of Concern?

“…The model proposed here is named XCH model and the authors claim that this model passes all the stiction parameter tests. di Capaci et al, [93] have reported a comparative description for modeling and detection of stiction in industrial control valves with different models. Here, modeling is achieved by considering the process as a linear part and stiction as a nonlinear part using a Hammerstein system.…”

Review of Energy-saving Technologies in Modern Hydraulic Drives

“…R (F) -internal model control system and with conditional feedback through the method of "the balance sensitivity equation" (Realtime control). This method can produce energysaving between 34…38% (Plummer 2016, Riccardo et al 2016.…”

Process control performance evaluation in the case of variable set‐point with experimental applications

“…Data-driven and model-based approach. In general terms, as alternative to the previous analytic formulas for IAE 0 and TV 0 (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26), is here also proposed to compute lower limits of performance indices by using values of IAE and TV from operating data, via (1) and 2. This means considering explicitly as reference performance the one that would be obtained by controlling the identified process modelP(s) with a hypothetical controllerĈ r (s) tuned according to SIMC rules.…”

“…Process parameters are identified with a FOPTD model, that is, a time-discrete linear Auto Regressive ARX(1, 1) model, and with a grid-search for the time-delay θ . [17] 3…”

“…If a pure linear model is used to identify the whole Hammerstein system (valve plus process), a strong model-mismatch would arise. The valve position could be estimated and stiction amount could be quantified through one of the many methods presented in the literature, [17] which also enables a correct identification of process dynamics.…”