Abstract
An internal model control with inverted decoupling (ID-IMC) controller design method based on equal fractional Butterworth (EFBW) filter is proposed for Multiple Input-Multiple Output (MIMO) systems with multiple time delays and Right Half Plane (RHP) zeros. There has been finite memory and limited flexibility for multivariable processes developed using a direct ID-IMC method. This paper presents a novel procedure to approximate Butterworth (BW) filters using fractional-order (FO) theories, so that the degree-of-freedom for tunable parameters is increased. The proposed ID-IMC controller cascaded with EFBW filter combines the computational simplicity of the ID-IMC structure with the greater flexibility of the EFBW filter, in conjunction with a better set-point tracking and disturbance rejection performance. Further, the stability analysis of the designed controller is given to ensure the stability of the closed-loop system. Dynamic performance indicators and sensitivity functions are carried out for the time domain and robustness analysis. Two illustrative examples are presented to show the merits of the proposed method.
Highlights
Most industrial processes have characteristics of Multiple Input-Multiple Output (MIMO), time delays, couplings and Right Half Plane (RHP) zeros, causing difficulties in feedback controller design
In [18], [22]–[23], the authors introduced a simple low-pass FO filter, with which an internal model control (IMC) structure was combined to construct the IMC-PID-FO-filter controller for single-input-single-output (SISO) system with time-delay and RHP zeros, which provided strong robustness and more degrees of freedom to meet other specifications
This paper provides a positive answer to the above challenging topic on new solutions to an inverted decoupling (ID)-IMC scheme with a FOBW filter, and the control system performance is analyzed
Summary
Most industrial processes have characteristics of Multiple Input-Multiple Output (MIMO), time delays, couplings and Right Half Plane (RHP) zeros, causing difficulties in feedback controller design. The authors in [16] proposed the decoupling IMC method for MIMO systems, a simple first order low-pass filter was introduced to attain a normal performance requirements. In [18], [22]–[23], the authors introduced a simple low-pass FO filter, with which an IMC structure was combined to construct the IMC-PID-FO-filter controller for single-input-single-output (SISO) system with time-delay and RHP zeros, which provided strong robustness and more degrees of freedom to meet other specifications. There may be strong couplings and time delays between input and output signals, which further complicate the feedback controller design [16] Under these circumstances, a simple low-pass IO/FO filter is not enough for an acceptable performance.
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