This paper deals with one of the possible ways to control multivariable (MIMO) control loops. The suggested control design procedure uses the so-called primary controllers, auxiliary controllers, and also correction members. Parameters of the primary controllers are determined for the optimal control pairs using arbitrary single-variable synthesis methods; namely, the modulus optimum method, the balanced tuning method, and the desired model method. The optimal control pairs are determined using the so-called relative gain array tool or the relative normalized gain array tool combined with other tools, as the condition number or the Niederlinski index. The auxiliary feedback controllers serve for ensuring a control loop decoupling. Invariance to load disturbance of a control loop is realized by using the correction members. The novelty lies especially in the combination of the original inverted decoupling with disturbance rejection and provided tuning methods. The proposed control design for a MIMO loop is verified by simulation for the two-variable controlled plant of a quadruple-tank process and evaluated by using various criteria. Moreover, a numerical comparison to some other methods is given to the reader. INDEX TERMS Control loop decoupling and invariance, multivariable control, optimal control pairs, quadruple-tank process, simulation.

Abstract. During the development of algebraic controller design in a special ring for time delay systems (TDSs) a problem of a suitable free controller parameters setting appeared. The first author of this contribution recently suggested a natural idea of placing the dominant characteristic numbers (poles) and zeros of the infinite-dimensional feedback control system on the basis of the desired overshoot for a simple finite-dimensional matching model and shifting of the rest of the spectrum. However, the original procedure called the Pole-Placement Shifting based controller tuning Algorithm (PPSA) was not developed and described entirely well. The aim of this paper is to revise the idea of the PPSA and suggest a possible ways how to improve or extend the algorithm. A concise illustrative example is attached to clarify the procedure for the reader as well.

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The paper deals with the description and simulation verification of one of possible methods to control of multivariable control loops. In this case, the so called main controllers, binding members and correction members are used. The proposed method of control combines classical way to ensure of autonomy of control loop via binding members and the use of the method of single-variable branched control loops with measurement of dominant disturbance variables to ensure of invariance of control loop via correction members. Main controllers can be proposed by arbitrary synthesis method. Simulation verifications of the control method are carried out for three-variable loop of a steam turbine.

The paper describes one of possible approaches to control of multi-variable control loop. In this case the so called main controllers, binding members and correction members are used for this one. Simulation verification of designed method of control is presented on three-variable control loop of steam turbine.