Internal Model Control Filter Research Articles

Combustion Control of Ship’s Oil-Fired Boilers Based on Prediction of Flame Images

This study proposes and validates a novel combustion control system for oil-fired boilers aimed at reducing air pollutant emissions through flame image prediction. The proposed system is easily applicable to existing ships. Traditional proportional combustion control systems supply fuel and air at fixed ratios according to the set steam load, without considering the emission of air pollutants. To address this, a stable and immediate control system is proposed, which adjusts the air supply to modify the combustion state. The combustion control system utilizes oxygen concentration predictions from flame images via SEF+SVM as control inputs and applies internal model control (IMC)-based proportional-integral (PI) control for real-time combustion control. Due to the complexity of modeling the image-based system, IMC filter constant tuning through experimentation is essential for achieving effective control performance. Experimental results showed that optimal control performance was achieved when the filter constant λ was set to 1.5. In this scenario, the peak overshoot Mp was reduced to 0.19245, and the Integral of Squared Error (ISE) was minimized to 10.1159, ensuring a stable response with minimal oscillation and maintaining a fast response speed. The results demonstrate the potential of the proposed system to improve combustion efficiency and reduce emissions of air pollutants. This study provides a feasible and effective solution for enhancing the environmental performance of marine oil-fired boilers. Given its ease of application to existing ships, it is expected to contribute to sustainable air pollution reduction across the maritime environment.

IMC based robust and innovative control strategies for higher-order DC-DC converter in DC microgrid applications

The extensive practice of DC-DC converter interfacing circuits to maintain DC link voltage in DC microgrid applications introduces unavoidable voltage regulation problems due to its nonlinearity. These unregulated voltages demean the performance and result in an unstable system. This brief proposes an internal model control (IMC) non-linear approach based robust proportional-integral-lead (PI-Lead) controller design for regulating a practical fifth-order DC-DC boost converter. The main innovation of this paper is the developed procedure for designing controller. The prominent feature of IMC filter coefficient is to fulfil the desired level of gain margin and phase margin to show the trade-off between performance and robustness. The proposed controller's performance is evaluated in the presence of uncertain disruptions and its effectiveness is verified by comparing it with the some conventional proportional-integral (PI) as well as with recently published IMC-proportional-integral-derivative (IMC-PID) and IMC-proportional integral derivative double derivative (IMC-PIDD2) controllers. The applicability of the proposed control methodology has been validated under varying supply and load current levels in presence of parametric uncertainty using a MATLAB/Simulink tool along with a low-cost microcontroller DSP F280379D based laboratory prototype.

A Study of PI Controller Tuning Methods Using the Internal Model Control Guide for a Ship Central Cooling System as a Multi-Input, Single-Output System

Since the variable-speed seawater pump and the three-way valve of a ship’s central cooling system are forms of feedback from the same output signal, these controllers may cause interference when they are not coordinated. Therefore, studying an efficient control tuning method for a central cooling water system is necessary. In this study, a central cooling water system is modeled using Matlab Simulink by utilizing an actual operation dataset, and unknown parameters are estimated for fine-tuning. The simulation model is then verified using the second operating dataset. Additionally, transfer functions are developed for the freshwater output temperature against the three-way valve openness input and the electrical power frequency input to the seawater pump motor, supposing that the two systems are independent. Then, the two PI controllers are tuned using internal model control (IMC) filters. Moreover, the modified internal model control tuning method is suggested, using the character of the central cooling system, which has a large time constant for the heat exchanger system with the seawater pump and a small time constant for the three-way valve system. This method simplifies the tuning of the two combined PI controllers, enhancing the seawater pump’s overall efficiency and the three-way valve’s operation. This study presents the proposed tuning methods based on the IMC filter and modified IMC guide, which confirmed the simple determination of the gain values of the PI controller with the efficient control of the rotational speed of the seawater pump and the three-way valve with reasonable control of the freshwater outlet temperature.

Robust control of discrete minimum and non‐minimum phase systems via data‐driven virtual reference feedback tuning and IMC

AbstractIn this paper, we develop a novel robust control approach for discrete minimum and non‐minimum phase systems via a combined data‐driven virtual reference feedback tuning () and internal model control (IMC) scheme. The first step in the conventional method controller design is the selection of the closed‐loop reference model (), and selection is still an open problem. The integration of the scheme and the VRFT method provides the advantage of flexibility in controller design due to the incorporation of the filter. As a result, the proposed design method begins with the selection of and filter. Unlike the standard method, the proposed combined and design approach has the unique feature of taking into account a robustness property of dynamics, namely, maximum sensitivity () as the design specification for the and IMC filter selection. Moreover, the proposed approach includes a robustness specification that resolves the trade‐off between performance and robustness in real‐time controller design. Furthermore, the robustness guarantee with plant uncertainties and controller fragility is elucidated. The proposed approach is validated using numerical simulations and experimental validation through the temperature control process. Compared to conventional controllers, experimental and simulation results show that the proposed controllers have less tracking error, minimize control effort, and improve robustness.

Fractional filter IMC-TDD controller design for integrating processes

A modified internal model control (IMC) with fractional-order tilt double derivative controller (FOTDD) is proposed for integrating processes. This method is extended for all three types of process models, namely, integrating plus time delay process (IPTD), double integrating plus time delay process (DIPTD) and integrating plus first order plus time delay process (IFOPTD). The feedback controller is designed in an IMC framework that can quickly obtain from the plant parameters. Then, the fractional IMC filter can be tuned from the obtained explicit expressions for easy access in practice. A numerical study is conducted with various examples from literature for all types of integrating models. The results are compared with current methods in terms of setpoint tracking, disturbance rejections and parameter perturbation. Even considering a fractional-order derivative controller, the results demonstrated a simple, robust structure with fewer tuning parameters.

Robust PIDD2 Controller Design for Perturbed Load Frequency Control of an Interconnected Time-Delayed Power Systems

The extensive practice of open communication links in the power system network introduces unavoidable communication time delays (CTDs). These CTDs demean the performance of the load frequency control (LFC) system, and in the worst condition, the LFC system becomes unstable. Thus, this brief proposes a robust proportional integral derivative double derivative (PIDD2) controller design for the perturbed LFC of the interconnected time-delayed power system. In this brief, the worst case plant selection approach is applied to find the worst case plant model using Kharitonov’s stability theorem of the interval system. The proposed PIDD2 controller is designed for the selected worst case plant model of the original interval plant. Furthermore, the tuning of PIDD2 controller is carried out using an internal model control (IMC) approach. The notable feature of the presented IMC scheme is that the IMC filter coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> ) is determined in terms of maximum sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{s}$ </tex-math></inline-formula> ) and CTD, which shows the tradeoff between robustness and performance. The proposed control scheme is validated on a two-area time-delayed power system model. The effectiveness and robustness of the proposed IMC-PIDD2 control approach are assessed under parametric uncertainties in system parameters as well as CTD, nonlinearities, and step load demand disturbances. Besides, delay margin (DM) is also computed in the sense of Walton and Marshall stability theorems for the proposed control system. The efficacy of the proposed IMC-PIDD2 control scheme is verified by comparing it with the recently reported control schemes.

An enhancement in series cascade control for non-minimum phase system

Abstract This work reveals an Internal Model Control (IMC)-based series cascade control for the non-minimum phase and time delay process. The combination of a higher-order fractional IMC filter and inverse response compensator for designing the outer loop controller illustrates the uniqueness of this work. For the time delay term, a higher-order approximation is considered. The standard IMC-PID structure adopts for the inner loop controller design. While the higher-order fractional filter coupled with inverse response compensator takes for the design of the outer loop controller. The suggested scheme demonstrates enhanced exhibition for setpoint tracking and disturbance rejection. Moreover, the sensitivity analysis is also accomplished to determine the robustness of the closed-loop system under process parameter variations.

A multiple-model based internal model control method for power control of small pressurized water reactors

Small pressurized water reactors (PWRs) usually have variable operating conditions and complex operating environments. It is significant to design a robust control system to ensure stable and satisfactory reactor power maneuvers under large uncertainties. This paper purposes a multiple-model based internal model control (IMC) method for power control of small PWRs. Six local transfer function models are first developed from a nonlinear reactor core model over the entire operating range. Then, six local power controllers are designed for a small PWR based on these local models using the IMC scheme. The IMC filter time constant is determined by the genetic algorithm based multi-objective optimization to keep good balance between the control performance and cost. The local controllers are connected by a probability-weighted multiple model approach to generate a global IMC system for the reactor. Dynamic simulation results of the small PWR under the IMC scheme as well as performance assessments of the IMC scheme against the PID control scheme during typical transient operations have shown good reference tracking performances and strong disturbance rejection capabilities of the multiple-model based IMC system, demonstrating the feasibility and effectiveness of the proposed method for the power control of small PWRs.

Analytical design of fractional IMC filter – PID control strategy for performance enhancement of cascade control systems

The cascade control is widely used in chemical industries for disturbance attenuation as an alternative to a single feedback loop. This article presents an internal model control (IMC)-based series cascade control system for different time delay process models. The novelty of the work lies in the use of fractional order IMC filter of the first order and higher order for designing controller in the outer loop based on specific maximum sensitivity. The design also considers different approximations for the time delay term. The controller designed for the inner loop assumes the standard PID controller structure and the outer loop controller takes a fractional filter PID structure. The proposed method gives improved performance for set point tracking and disturbance rejection. Further, the proposed method gives robust performance for noise in the measured signal. Also, the robustness analysis is performed to know the insensitivity of the closed-loop system for process parameter variations. The fragility of the controller is investigated for perturbations in the controller parameters.

Optimised control using proportional-integral-derivative controller tuned using internal model control

Time delays are generally unavoidable in the designing frameworks for mechanical and electrical systems and so on.. In both continuous and discrete schemes, the existence of delay creates undesirable impacts on the under-thought which forces exacting constraints on attainable execution.The presence of delay confounds the design structure procedure also. It makes continuous systems boundless dimensional and also extends the readings in discrete systems fundamentally. As the Proportional-Integral-Derivative (PID) controller based on internal model control is essential and strong to address the vulnerabilities and aggravations of the model. But for an real industry process, they are less susceptible to noise than the PID controller.It results in just one tuning parameter which is the time constant of the closed-loop system λ, the internal model control filter factor.It additionally gives a decent answer for the procedure with huge time delays. The design of the PID controller based on the internal model control, with approximation of time delay using Pade’ and Taylor’s series is depicted in this paper. The first order filter used in the design provides good set-point tracking along with disturbance rejection.

Novel IMC filter design-based PID controller design for systems with one right half plane pole and dead-time

In this article, design of PID controller using a modified internal model control (IMC) filter for right half plane (RHP) pole process with dead time is proposed. To possess H2 optimal behaviour, the derived IMC controller minimises the integral square error (ISE) for step input disturbances by defining the Blaschke product of unstable poles of the specific input and the model. Then it is converted into a single feedback loop controller as either PID or PID with first order filter on the basis of proposed underdamped IMC filter to improve the integral action and thereby providing fast response which is not feasible with critically damped filter. Maclaurin series approximation is used to design PID controller and Pade's approximation is used to design PID with first order lead lag filter. Various first order plus dead time (FOPDT) examples are taken and simulation is executed on diverse unstable processes and compared with some of the developed methods available in the literature. The two proposed controllers provide improved responses with respect to both nominal and perturbed conditions. The robustness studies have also been carried out for uncertainties in the plant dynamics and it is apparent that the proposed tuning method is robust.

Novel IMC filter design-based PID controller design for systems with one right half plane pole and dead-time

In this article, design of PID controller using a modified internal model control (IMC) filter for right half plane (RHP) pole process with dead time is proposed. To possess H2 optimal behaviour, the derived IMC controller minimises the integral square error (ISE) for step input disturbances by defining the Blaschke product of unstable poles of the specific input and the model. Then it is converted into a single feedback loop controller as either PID or PID with first order filter on the basis of proposed underdamped IMC filter to improve the integral action and thereby providing fast response which is not feasible with critically damped filter. Maclaurin series approximation is used to design PID controller and Pade's approximation is used to design PID with first order lead lag filter. Various first order plus dead time (FOPDT) examples are taken and simulation is executed on diverse unstable processes and compared with some of the developed methods available in the literature. The two proposed controllers provide improved responses with respect to both nominal and perturbed conditions. The robustness studies have also been carried out for uncertainties in the plant dynamics and it is apparent that the proposed tuning method is robust.

Analytical Design of Enhanced Fractional Filter PID Controller for Improved Disturbance Rejection of Second Order Plus Time Delay Processes

Abstract In this article, a modified fractional internal model control (IMC) filter structure is proposed to design a fractional filter Proportional-Integral-Derivative (FFPID) controller for improved disturbance rejection of second order plus time delay (SOPTD) processes. The proposed method aims at improving the disturbance rejection of slow chemical processes as the tuning rules for such processes are limited. The present design also considers the higher order approximation for time delay as it gives improved response for higher order processes. There is an additional tuning parameter in the proposed IMC filter apart from the conventional IMC filter time constant, which is tuned according to the derived formula. The additional adjustable parameter achieves the disturbance rejection and the closed loop stability. The simulation results have been performed for the same degree of robustness (maximum sensitivity, Ms) for a fair comparison. The results show an improved disturbance rejection for lag dominant and delay significant SOPTD processes with the proposed controllers designed using higher order Pade’s approximation of time delay than the proposed method using first order approximation and the conventional method. The closed loop robust performance is observed for perturbations in the process parameters and the performance is also observed for noise in the measurement. The robust stability analysis is carried out using sensitivity functions. In addition, the Ms range is also identified over which the system gives robust performance for the controllers designed using higher order pade’s approximation of time delay compared to conventional method.

Graphic IMC-PID tuning based on maximum sensitivity for uncertain systems

Obtaining all feasible parameters of the proportional-integral-differential (PID) controller is the key goal in uncertain systems. This paper proposes a graphical tuning method based on an internal model control (IMC) strategy for uncertain systems with time delay. Specifically, the Kharitonov theorem is introduced first to simplify the uncertain system into 32 polynomials. Then, for each polynomial, the IMC structure is applied to reduce the tuning parameters of the PID controller in order to rapidly determine the controller parameters. Finally, the maximum sensitivity (Ms) is used to further guarantee the controlled system with a certain robustness and dynamic performance, which can portray constant gain margin and phase margin boundaries, and can even determine the range of parameters of the proposed IMC filter. Three example results from simulations are presented to demonstrate the effectiveness and applicability of the proposed method.

Fractional filter IMC-PID controller design for second order plus time delay processes

AbstractThis article presents a simple method of designing a fractional filter PID controller for second order plus time delay (SOPTD) processes using internal model control (IMC) scheme. There has been limited number of tuning rules for SOPTD processes developed using direct synthesis method and IMC method. The proposed IMC-PID controller using fractional IMC filter results in a controller structure composed of PID controller cascaded with fractional filter. Simulations have been performed on several second order lag dominant and delay significant processes. Robustness checks are performed for variations in the process parameters and robustness analysis is carried out using sensitivity functions. The proposed controller results in an enhanced control performance for nominal process parameters and with parameter variations. In addition, the effect of measurement noise is also studied for set point tracking and load disturbance variations.

Design of internal model control-proportional integral derivative controller with improved filter for disturbance rejection

The internal model control (IMC) proportional integral derivative (PID) controller tuning rules provide an excellent tracking of set-point, but sluggish disturbance rejection, as the conventional IMC filter introduces slow process pole. Disturbance rejection is significant than set-point tracking in many industrial applications. This paper proposes the design of IMC-PID controller, cascaded with lead–lag filter, with an improved IMC filter to provide effective disturbance rejection and robust operation of the first-order processes (FOPs). The simulation study was conducted to show the effectiveness of the proposed method on various structures of the FOPs, calculating the controller parameters, maintaining similar robustness in terms of maximum sensitivity MS. Perturbations were incorporated in the parameters of the plant model simultaneously, for the robustness analysis of the controller. The closed-loop performance was evaluated with the integral error criteria, namely, integral absolute error, integral square error, and integral time absolute error. The proposed IMC filter provided good disturbance rejection. The results of recently published design methods were compared with that obtained from the proposed method, validating the usefulness of the proposed method.

A Study of the Dynamics and Control of the Model IV Fluidized Catalytic Cracking Process

Fluid catalytic cracking (FCC) is one of the most important chemical units in oil refineries due to its economic benefits. This research work concentrates on improving the control system of the Model IV FCC unit where dynamic modeling and the controllability based on the McFarlane et al. (1993) model. Different open-loop tests were carried out in the wash oil flow rate (F1) and the furnace fuel flow rate (F5) to find the FCC models using Sundaresan and Krishnaswamy (S&amp;K) and fraction incomplete response (FIR) methods. The riser temperature (Tr) and the regenerator bed temperature (Tg) were chosen as the control variables while (F1 and F5) were selected as the corresponding manipulated variables based on the relative gain array (RGA). PI controller tuning parameters were evaluated using the internal model control (IMC) method and different closed-loop control responses were examined for both set point tracking and disturbance rejection changes. Additional adjustments to the IMC filter constant were employed to further improve the closed loop responses for the system.

Load Frequency Control in Power Systems via Internal Model Control Scheme and Model-Order Reduction

The large-scale power systems are liable to performance deterioration due to the presence of sudden small load perturbations, parameter uncertainties, structural variations, etc. Due to this, modern control aspects are extremely important in load frequency control (LFC) design of power systems. In this paper, the LFC problem is illustrated as a typical disturbance rejection as well as large-scale system control problem. For this purpose, simple approach to LFC design for the power systems having parameter uncertainty and load disturbance is proposed. The approach is based on two-degree-of-freedom, internal model control (IMC) scheme, which unifies the concept of model-order reduction like Routh and Pade approximations, and modified IMC filter design, recently developed by Liu and Gao [24]. The beauty of this paper is that in place of taking the full-order system for internal-model of IMC, a lower-order, i.e., second-order reduced system model, has been considered. This scheme achieves improved closed-loop system performance to counteract load disturbances. The proposed approach is simulated in MATLAB environment for a single-area power system consisting of single generating unit with a non-reheated turbine to highlight the efficiency and efficacy in terms of robustness and optimality.

Multi-loop nonlinear internal model controller design under nonlinear dynamic PLS framework using ARX-neural network model

In this paper, a novel multi-loop nonlinear internal model control (IMC) strategy for multiple-input multiple-output (MIMO) systems is presented under the partial least squares (PLS) framework, which automatically decomposes the system into several univariate subsystems in the latent space. To formulate a nonlinear dynamic PLS framework, we propose an ARX-neural network (ARX-NN) cascaded structure, and incorporate it into PLS inner model. A gradient-based optimization approach is then provided to identify the parameter sets of the ARX-NN PLS model so that the plant-model mismatch is minimized. Furthermore, with perfect model, we show that the response of the closed loop system can be reduced to a simple linear IMC filter with the original system delay. The simulation results of a methylcyclohexane (MCH) distillation column from Aspen Dynamic Module, demonstrate the effectiveness of our approach in terms of disturbance rejection and tracking performance.

Design of IMC filter for PID control strategy of open‐loop unstable processes with time delay

AbstractA modified internal model control (IMC) filter has been proposed for the open‐loop unstable process with time delay and a further IMC–proportional‐integral‐derivative (PID) tuning rule is derived on the basis of the proposed IMC filter. Investigation of the IMC filter structure clearly demonstrates that a critically damped filter does not always provide satisfactory response and that this is probably due to lack of sufficient integral action. The conventional, critically damped filter is therefore replaced with a more general, second‐order IMC filter for improved integral action. The present investigation shows that for the most unstable processes, the underdamped IMC filter provides the desired integral action and improves the closed‐loop performance of the system except for the unstable processes with a strong lead term. An exhaustive simulation studies has been performed to show the advantage of the proposed method in both nominal and robust cases. By incorporating Kharitonov's theorem, closed‐loop time constant (λ) guidelines have been provided for the first‐order delayed unstable process (FODUP). Copyright © 2010 Curtin University of Technology and John Wiley &amp; Sons, Ltd.