Nonlinear process identification and friction quantification in control valves. / Identificação de processos não-lineares e quantificação de atrito em válvulas de controle.
AUTOR(ES)
Rodrigo Alvite Romano
DATA DE PUBLICAÇÃO
2009
RESUMO
The friction in control valves and inadequate controller tuning are two of the major sources of performance degradation in control loops that include such devices. As friction models are needed to diagnose abnormal valve operation or to compensate such undesirable effects, process models play an essential role in controller design. This work extends existing methods that jointly identify the friction and process model parameters, so that a nonlinear structure is adopted to represent the process model. The procedure is based on data from closed-loop experiments. The developed estimation algorithms are tested with data from simulations and generated by a hybrid setup (composed of a real valve and a simulated pH neutralization process), in which the influences of the process disturbances, of the excitation signal magnitude and of the controller tuning on estimated models are investigated. The results demonstrate that the friction is accurately quantified, as well as good process models are estimated in several situations. In addition, the proposed extension presents significant advantages in relation to other methods, such as: (1) greater accuracy for friction quantification, especially for highly nonlinear processes and (2) reasonable estimates of the nonlinear steady state characteristics.
ASSUNTO(S)
pneumatic control valves nonlinear optimization friction identificação de sistemas otimização não-linear atrito system identification válvulas de controle pneumático
