Practical advantages of inverted decoupling

Abstract

This paper presents a study of the main advantages of inverted

Centralized Inverted Decoupling Control

“…Some mechanisms are based on the tracking mode of the final controller output. 32 In addition and similar to inverted decoupling, 25 when the controller outputs are used as cascade setpoints to lower level controllers, each decoupled control loop is immune to abnormalities (e.g., a valve at a limit or a secondary controller in manual) in the secondary of the other loops. To obtain this decoupling performance, it is necessary to measure the output signals of the secondary loops and to feed back them through the elements of Ko(s).…”

“…A gain margin of 10 is chosen as specification in the three loops. The gains k 1 and k 3 are calculated by means of (25). In the second open loop process l 2 (s), the time constant λ of the extra pole is obtained from (28) after specifying ω cp =0.63 rad/min.…”

Centralized multivariable control by simplified decoupling

“…An alternative decoupling method, called inverted decoupling, maintains very simple apparent processes and decoupler elements independently of the system size [14]. In addition, inverted decoupling presents several practical advantages on implementation [15]. Nevertheless, the method also has an important disadvantage: because of stability problems, it cannot be applied to processes with multivariable right half plane (RHP) zeros, that is, RHP zeros in the determinant of the process transfer matrix G(s).…”

“…Therefore, the realizability of each configuration {p 1 -p 2 -…-p j -…-p n-1 -p n } can be analyzed, determining the necessary extra dynamics with (15). Then, the elements of D(s) and Q(s) can be obtained using (16) and (17), respectively.…”

“…After this approximation, the extra dynamics N(s) needed to achieve realizability for the different configurations are obtained according to (15) and the nine possible apparent processes q i (s) are obtained with (17). The only configuration without extra dynamics is the configuration 3-3-3.…”