Truong Nguyen Luan Vu

Analytical design of fractional-order proportional-integral controllers for time-delay processes.

A new design method of fractional-order proportional-integral controllers is proposed based on fractional calculus and Bodes ideal transfer function for a first-order-plus-dead-time process model. It can be extended to be applied to various dynamic models. Tuning rules were analytically derived to cope with both set-point tracking and disturbance rejection problems. Simulations of a broad range of processes are reported, with each simulated controller being tuned to have a similar degree of robustness in terms of resonant peak to other reported controllers. The proposed controller consistently showed improved performance over other similar controllers and established integer PI controllers.

Multi-loop PI controller design based on the direct synthesis for interacting multi-time delay processes

In this article, a new analytical method based on the direct synthesis approach is proposed for the design of a multi-loop proportional-integral (PI) controller. The proposed design method is aimed at achieving the desired closed-loop response for multiple-input, multiple-output (MIMO) processes with multiple time delays. The ideal multi-loop controller is firstly designed in terms of the relative gain and desired closed-loop transfer function. Then, the standard multi-loop PI controller is obtained by approximating the ideal multi-loop controller using the Maclaurin series expansion. The simulation study demonstrates the effectiveness of the proposed method for the design of multi-loop PI controllers. The multi-loop PI controller designed by the proposed method shows a fast, well-balanced, and robust response with the minimum integral absolute error (IAE).

IMC-PID approach: An effective way to get an analytical design of robust PID controller

In this paper, the analytical PID controller design methodology of the SISO and MIMO processes has been discussed on the basis of the IMC principle. The paper deals with two issues: firstly emphasizes on a tuning method of a SISO stable and unstable process and secondly a MIMO tuning rule. To verify the superiority of the proposed tuning method, simulation studies have been conducted on several process models. The results show that the proposed tuning method has a convincing result for wide classes of process models. The robustness analysis is also carried out by inserting a perturbation in each of the process parameters simultaneously, with the results demonstrating the better robustness of the proposed controller design with parameter uncertainty.

A unified approach to the design of advanced proportional-integral-derivative controllers for time-delay processes

A unified approach for the design of proportional-integral-derivative (PID) controllers cascaded with first-order lead-lag filters is proposed for various time-delay processes. The proposed controller’s tuning rules are directly derived using the Padé approximation on the basis of internal model control (IMC) for enhanced stability against disturbances. A two-degrees-of-freedom (2DOF) control scheme is employed to cope with both regulatory and servo problems. Simulation is conducted for a broad range of stable, integrating, and unstable processes with time delays. Each simulated controller is tuned to have the same degree of robustness in terms of maximum sensitivity (Ms). The results demonstrate that the proposed controller provides superior disturbance rejection and set-point tracking when compared with recently published PID-type controllers. Controllers’ robustness is investigated through the simultaneous introduction of perturbation uncertainties to all process parameters to obtain worst-case process-model mismatch. The process-model mismatch simulation results demonstrate that the proposed method consistently affords superior robustness.

Smith predictor based fractional-order PI control for time-delay processes

A new fractional-order proportional-integral controller embedded in a Smith predictor is systematically proposed based on fractional calculus and Bode’s ideal transfer function. The analytical tuning rules are first derived by using the frequency domain for a first-order-plus-dead-time process model, and then are easily applied to various dynamics, including both the integer-order and fractional-order dynamic processes. The proposed method consistently affords superior closed-loop performance for both servo and regulatory problems, since the design scheme is simple, straightforward, and can be easily implemented in the process industry. A variety of examples are employed to illustrate the simplicity, flexibility, and effectiveness of the proposed SP-FOPI controller in comparison with other reported controllers in terms of minimum the integral absolute error with a constraint on the maximum sensitivity value.

Fractional-order PI controllers design based on IMC scheme for enhanced performance of dead-time processes

A unified method for the fractional-order proportional-integral controller based on IMC scheme (IMC-FOPI) is proposed. The analytical tuning rules are derived for achieving the performance improvement in terms of both disturbance rejection and set-point tracking. Many illustrative examples are considered to confirm the effectiveness of the proposed algorithm for both integer and fractional-order processes with time delays. In addition, the robust stability of fractional-order systems are also carried out in order to demonstrate that the proposed controller can hold well the robustness against perturbation uncertainty in the process models.

Analytical Design of Robust Multi-loop PI Controller for Multi-time Delay Processes

In this chapter, a robust design of multi-loop PI controller for multivariable processes in the presence of the multiplicative input uncertainty is presented. The method consists of two major steps: firstly, the analytical tuning rules of multi-loop PI controller are derived based on the direct synthesis and IMC-PID approach. Then, in the second step, the robust stability analysis is utilized for enhancing the robustness of proposed PI control systems. The most important feature of the proposed method is that the tradeoff between the robust stability and performance can be established by adjusting only one design parameter (i.e., the closed-loop time constant) via structured singular value synthesis. To verify the superiority of the proposed method, simulation studies have been conducted on a variety of the nominal processes and their plant-model mismatch cases. The results demonstrate that the proposed design method guarantees the robustness under the perturbation on each of the process parameters simultaneously.

Design of Advanced Multi-loop PI Controller for Multi-delay Processes

An analytical method for robust design of the multi-loop proportional-integral (PI) controller is proposed for various types of multi-delay processes. On the basis of the direct synthesis and generalized IMC-PID approach, the analytical tuning rules of the multi-loop PI controller are firstly derived for achieving the desired closed-loop response, and the structured singular value synthesis is then utilized for the tradeoffs between the robust stability and performance by adjusting only one design parameter (i.e., the closed-loop time constant). To verify the superiority of the proposed method, the simulation studies have been conducted on a wide variety of multivariable processes. The multi-loop PI controller designed by the proposed method shows a fast, well-balanced and robust response with the minimum integral absolute error (IAE) in compared with other renowned methods.