Internal Model Control Controller Research Articles

Novel tuning rules for IMC-high-order PID load frequency controller of power systems

The problem of load frequency control (LFC) for power grids has received widespread attention in power industrial control. Ensuring the stability of the frequency is the primary concern that constrains the development of the electric power system. This paper presents a novel internal model control (IMC)- proportional-integral-derivative (PID) controller design method for LFC control systems, centered on pole-zero conversion. This method aims to simplify the system model's complexity and improve the system's performance. The IMC controller is approximated as a PID series compensator (high-order PID), with exact tuning formulas provided for various scenarios. These include single-area without or with reheat turbines, hydro turbines with transient droop compensators, wind turbines, and gas turbines. The tuning formulas are characterized by a single parameter, determined under robustness constraints and integrated time absolute error (ITAE). The proposed tuning method considers the generator rate constraint (GRC) and applies to multi-area single-source and multi-area multi-source power systems. The results of the simulation confirm that the controller tuning method presented in this paper has significant advantages over the existing design methods concerning robustness and anti-interference performance.

An adaptive internal model control approach for unmanned surface vehicle based on bidirectional long short-term memory neural network: Implementation and field testing

This paper investigates a practical adaptive internal model control (IMC) for an unmanned surface vehicle (USV) with unknown time-varying nonlinear model parameters and environmental disturbances. Firstly, an internal model of the USV is presented using the Bidirectional Long Short-Term Memory (BiLSTM) neural network. Then, an adaptive neural IMC controller is designed for the trajectory tracking of USV by using the IMC method. The internal model and the controller are updated by an error threshold algorithm. The proposed control scheme comprises of a trajectory guidance module via the Line-of-Sight (LOS) guidance method and a tracking control module designed by IMC theory. Under the proposed control scheme, the development processes of the vehicle platform and the control algorithms are described, and accurate tracking control can be achieved. Finally, the results of simulation and field experiments are presented and discussed to validate the effectiveness of the proposed control scheme.

Robust controller for artificial pancreas for patients with type-1 diabetes

The target of this paper is to design a simple and an efficient controller for artificial pancreas (AP) system for blood glucose (BG) regulation in type-1 diabetic mellitus (T1DM) patient. Bergman’s intravenous model is chosen for the controller design as the model is minimum ordered model of T1DM patient. A multi-objective output feedback controller has been designed for AP system considering robustness, disturbance rejection, and transient criterion. Considering H∞, pole-placement, and H2 constraints, a control algorithm has been developed and has been solved using linear matrix inequality (LMI) technique. As a testing platform of the intravenous model-based designed controller, UVa/Padova T1DM metabolic simulator has been chosen which uses subcutaneous insulin delivery method. The controller has been tested in the presence of unannounced meal disturbances. Experimental results show that the controller regulates BG level very efficiently with lesser amount of insulin and avoids hypoglycemia effect. In the presence of external noises like glucose sensor noise and insulin pump error, the robustness of the controller has been checked. The performance of the controller has been compared with compound internal model control (IMC) strategy reported earlier for same meal scenario. The designed multi-objective controller gives better performance metrices than compound IMC controller.

TUNING OF IMC CONTROLLER FOR SYSTEMS WITH TIME-DELAY USING AN IMPROVED STRANGE NONCHAOTIC OPTIMIZATION APPROACH

The internal model control (IMC) has received extensive attention due to strong robustness, while it is challenging to tune the parameters of the controller. So far, strange nonchaotic optimization algorithm, based on grazing bifurcation, has been proposed to tune the parameters of the IMC controller in some recent progress, which processes a strong ability to escape from local optimization. However, the nonuniformity of the strange nonchaotic sequence distribution can result in insufficient optimization capability. In this paper, in order to obtain an excellent optimization effect, an improved strange nonchaotic optimization algorithm (ISNOA) based on grazing bifurcation is proposed to tune the parameters of the IMC controller. First, the boundary of a strange nonchaotic sequence is redefined by analyzing the strange nonchaotic sequence distribution. Furthermore, normalization function is applied to determine the optimization space. Consequently, the proposed ISNOA has better ability to escape from the local minima, higher stability and finer performance than the general SNOA, which is more suitable to tune the parameters of the IMC controller. Simulation results illustrate the effectiveness of ISNOA. In addition, for mismatch model, numerical simulations demonstrate the good performance of the control system based on ISNOA, meanwhile, the ISNOA is also demonstrated to be superior to particle swarm optimization (PSO).

Low‐gain internal model control PID controller design based on second‐order filter

AbstractA design method is proposed for low‐gain internal model control (IMC) proportional‐integral‐derivative (PID) controllers based on the second‐order filter. The PID parameters are obtained by approximating the feedback form of the IMC controller with a Maclaurin series, in which the second‐order filter is applied using the IMC approach to achieve a low‐gain PID controller that is suitable for model mismatch problems. Analytical PID tuning rules based on the second‐order filter are derived for several common‐use process models. The second‐order filter is designed from the desired time domain performances of maximum overshoot and settling time. Furthermore, the robustness of the IMC PID controller based on the second‐order filter is analyzed, and results show that its robustness performance is better than the first‐order filter under certain conditions. Finally, three categories of models divided by the ration of time constant and time delay are presented in the comparative numerical simulations to validate the effectiveness and generality of the proposed PID controller design method.

A PID Control Method Based on Internal Model Control to Suppress Vibration of the Transmission Chain of Wind Power Generation System

Vibrations occur in the wind turbine drivetrain due to the drivetrain’s elasticity and gear clearance. Typically, the PID control method is used to suppress elastic vibration, while the method with the disturbance suppression function is used to suppress nonlinear gear clearance vibration. The purpose of this paper is to propose an equivalent PID control method based on the internal model control (IMC) for suppressing vibration caused by the wind turbine drivetrain’s elasticity and gear clearance. The equivalent PID controller can suppresses elastic vibration; the IMC controller can suppresses gear clearance vibration. First, the vibration principle of the two-mass wind turbine drivetrain with clearance is discussed. After analyzing the nonlinear characteristics of the gear clearance, the nonlinear clearance system is decomposed into a linear unit and a nonlinear bounded disturbance unit. To suppress nonlinear bounded disturbances, a disturbance suppression method based on IMC is proposed; simultaneously, an equivalent PID controller based on IMC is designed to resolve the vibration issue caused by the wind turbine drivetrain’s elasticity. The simulation experimental results show that the clearance vibration is suppressed by the original IMC method. The PID controller obtained by the IMC equivalent transformation can suppress the elastic vibration.

Modified proportional integral controller for single ended primary inductance converter

The article highlights and optimizes a controller for the single ended primary inductance converter (SEPIC) direct current-direct current (DC-DC) converter. The SEPIC converter adjusts a range of dc input voltages and delivers a constant and stable output voltage. Three different models of the SEPIC converter are presented in order to derive its transfer function. Being a 4th order, an approximation method for the reduction of this transfer function to 2nd and 1st order is implemented. Two methods for controlling the converter are presented, the first one is based on guessing techniques and the second explains the design steps of the controller based on the internal model control (IMC). Furthermore, an improvement on the IMC controller is proposed and results were shown and discussed. IMC is based on integrating the “process model” in the control operation of the actual system. By using an approximation of the original transfer function of the system, it is expected that the IMC control will be able to achieve the desired results. Control schemes of the SEPIC will be presented and results will be shown. The response of the controller was tested with mathematical models for batteries and supercapacitors in MATLAB, as non-ideal DC-sources, and results were presented.

Two-harmonic Periodic Disturbance Compensation for Dead-Time Processes with Online Identification of Input Delay

As in the case of the Smith predictor, when applied to dynamical systems with delay in the input, the stability of the internal model control (IMC) system can be very sensitive to the mismatch that can occur between the plant delay and the identified delay. In this paper, we propose an online identification technique for the plant with input delay, which is used to adapt an IMC controller designed to reject periodic disturbances consisting of two harmonics. The proposed method is based on wavelet analysis and cross-correlation of the measured output. Moreover, the proposed controller structure introduces a novel analytical approach which makes it suitable for the adaptive application. The practical motivation of the study is to address the delay mismatch that can be caused by approximating time-varying high-order systems by first-order models with input delay. The approach is numerically validated.

2DOF IMC and Smith-Predictor-Based Control for Stabilised Unstable First Order Time Delayed Plants

The article brings a brief revision of the two-degree-of-freedom (2-DoF) internal model control (IMC) and the 2-DoF Smith-Predictor-based (SP) control of unstable systems. It shows that the first important reason for distinguishing between these approaches is the limitations of the control action. However, it also reminds that, in addition to the seemingly lucrative dynamics of transients, the proposed approaches can conceal a tricky behavior with a structural instability, which may manifest itself only after a longer period of time. Instead, as one of possible reliable alternatives, two-step IMC and filtered Smith predictor (FSP) design are applied to unstable first-order time-delayed (UFOTD) systems. Firstly, the 2-DoF P controller yielding a double real dominant closed loop pole is applied. Only then the 2-DoF IMC or FSP controllers are designed, providing slightly slower, but more robust transients. These remain stable even in the long run, while also showing increased robustness.

IMC Based PID Controllers Retuning and Its Performance Assessment

Internal Model Control (IMC) is the basis of a systematic program Q on the parameters of the concept and is based on the many modern control technology control system design. The present research work presents a novel control scheme for tuning PID controllers using Internal Model control with the filter time constant optimized using Bee colony Optimization technique. The robustness is measured by a two-block structured singular value, and the disturbance rejection is measured by the minimum singular value of the integral gain matrix. PID controllers are used widely in Industrial Processes. Criteria based on disturbance rejection and system robustness are proposed to assess the performance of PID controllers. Tuning of PID controllers is accomplished using Internal Model control scheme. In this paper, we propose an optimal filter design IMC IMC-PID controller for unstable process better set point tracking. IMC includes tuning of filter constant λ. The controller is suitable for different values of the filter tuning parameters to achieve the desired response in due IMC method is based on pole-zero offset, including IMC design principle method causes the response sets a good point. However, in a stable long lag time of load disturbances leading to undesirable process which is the result of the IMC control industry. Therefore, IMC has been a popular design process processing industry, especially as a means for adjusting the single-loop, PID controllers.

Experimental investigation of model-based IMC control of severe slugging

Severe slugging formation has been investigated experimentally in a two-phase flow-loop composed of a downwardly inclined pipe and a vertical riser. In this study, a bifurcation diagram was made to more clearly identify which flow the current system has at each valve opening. A model was made by inputting the dimensions of the flow loop using OLGA, a multiphase flow simulation program, to compare the experimental results. The model-based control logic was constructed by estimating the transfer function utilizing the OLGA model. The estimated transfer function is used to tune the gain of the PI controller, using the method called the Internal Model Control (IMC). Through this method, PI gain can be easily obtained through only one tuning parameter. When the PI controller gain is obtained through the transfer function of the flow loop system, mitigation of severe slugging was achieved while increasing the flow rate than the case with manual choking.

Decoupling internal model control for the robust engagement of clutches

Research on the robustness of clutch engagement control is attracting considerable interest because of its wide applications in advanced powertrains. Internal model control (IMC) is advantageous because it can handle model errors and external disturbances with light computational loads. However, during clutch engagement, two control inputs (engine output torque and clutch transmitted torque) and two system outputs (driving speed and the driven part of the clutch) are coupled; moreover, the two reference inputs are considerably different. A method for directly decoupling and stabilizing multi-input multi-output systems controlled by a two-degree-of-freedom (2DOF) IMC is proposed based on the construction of V-canonical matrices. The proposed method allows simple expressions for the control algorithm to be obtained without computing an inverse matrix that is used conventionally. Two filters, considering both the reference inputs and system characteristics, are independently designed considering the decoupling operation. The simulation results show that the proposed decoupling 2DOF IMC gains a considerably less tracking error and better robustness to model error and disturbance compared to classical 2DOF IMC and model predictive control. The performance is validated via dynamometer experiments.

Weighted Internal Model Control-Proportional Integral Derivative Control Scheme Via Fractional Gradient Descent Algorithm

Abstract An adaptive controller design technique based on internal model control (IMC) scheme is proposed in this paper. Multiple IMC controllers having different values of filter time constants and exhibiting widely different performance are combined via weight update rule. The weight update rule, formulated via convex combination of integral and fractional order gradient descent algorithms, assigns time varying weights to individual candidate controllers to obtain an enhanced performance over the individual candidate controllers. The beauty of the proposed technique is that it employs the simplicity of one degree-of-freedom (1DOF) IMC structure to achieve an improved performance over existing 2DOF control schemes. The efficacy of the proposed technique is demonstrated via three illustrative examples and via experimental validation on the hardware setup of dc servosystem. An extensive comparative analysis in terms of simulation plots and performance indices offers a testimony to the effectiveness of the proposed scheme.

DC Motor Speed Control using Internal Model Controller Industrial Transformation Strategy

In developed nations, industries are made to function at control engineering costs via the use of appropriate control schemes for dc motors. This paper introduces the role played by dc motors in industries thereby necessitating the analysis and performance validation of dc motor in Internal Model Control (IMC) scheme as against the Proportional– Integral–Derivative (PID) control schemes that is widely used in most industries. Theories on dc motor model, PID and IMC controller were detailed to paved the way for the methodical approach of getting specifications and transfer function for a typical dc motor (model RMCS-3011). Matlab/Simulink software was then used to tune the PID controller for the purpose of finding the values of PID gains that meets the design requirements to achieve best performance, thereby enabling the simulation of the PID controller. Using Matlab m-file environment, IMC controller transfer function was generated and simulated. The IMC controller transfer function aimed at achieving a unity gain that tracks the set-point was approximately realized. In the realization process, it was obvious that a filter is required. The aim of this work is to evaluate the performance of the IMC controller over PID controller. Simulated plots in Matlab-Simulink using the PID gains for the PID controller, and time constants and filter order for the IMC were presented. The quantitative results of the IMC method when compared with that of PID control provides a commendable performance. However, the performance in terms of rise time is small and preferred with the use of Matlab-Simulink tuned PID controller. Conclusively, IMC controller would be the preferred controller where the robustness and accuracy of the dc motor speed control counts more than faster response

An internal model control design method for failure-tolerant control with multiple objectives

The selection of control structure is a critical step in the design of a control system since it can largely affect the achievable control performance. This paper presents a general internal model control (IMC) structure with multiple degrees-of-freedom for the design of control systems with multiple objectives (i.e., reference tracking and load and output disturbance rejection), so that controllers are designed independently of each other. The optimal performance of controllers is shown to remain intact when a controller is taken off-line, for example, due to actuator and/or sensor failures. This feature circumvents the need to redesign the remaining on-line controllers for optimal failure-tolerant control. The proposed control approach is used to derive IMC control structures for multi-loop cascade and coordinated control systems. The performance of the control approach is demonstrated on a simulated thin-film drying process in continuous pharmaceutical manufacturing for several multi-loop control structures and a variety of control-loop component failures.

Internal Model Control and Experimental Study of Ankle Rehabilitation Robot

SUMMARYIn the present work, the ankle rehabilitation robot (ARR) dynamic model that implements a new series of connection control strategies is introduced. The dynamic models are presented in this regard. This model analyzes the robot LuGre friction model and the nonlinear disturbance model. To improve the ARR system’s rapidity and robustness, a composite 2-degree of freedom (2-DOF) internal model control (IMC) controller is presented. The control performance of the compound 2-DOF IMC controller is simulated and analyzed in the present work. The simulation shows that the composite 2-DOF IMC controller has high following performance. For practical testing purposes, 1-DOF passive training and predetermined trajectory following have been completed for different swing amplitudes and frequencies. Moreover, the thrust and tension torque of the robotic dynamic and static loading characteristics are studied in active control mode. The experimental results show the effectiveness of passive training of the given trajectory and impedance training active control strategy. This paper gives the specific functions of ARR.

An Internal Model Control-Based Approach for Characterization and Controller Tuning of Turbocharged Gasoline Engines

This brief develops a method for system characterization and controller tuning for the boost control system of automotive turbocharged gasoline engines. The method utilizes the relay feedback technique for system characterization, followed by the internal model control (IMC) technique for controller tuning. The novelty is that instead of a high fidelity plant model, an ultrasimplified gain-integrator-delay model is employed in the IMC controller. As we show, our method leads to a time-efficient calibration process, assigns a desired closed-loop bandwidth exactly , and leads to good stability margins. A detailed and thorough analysis of the method, including its fundamental limitations, is provided. The method is experimentally applied to the boost control system of a turbocharged gasoline engine, where it is shown that the controller gains can be reliably computed at various engine operating points. The method identifies turbocharger speed as the best scheduling parameter for the controller gains, and the resulting controller is experimentally shown to yield good tracking performance.

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.

Fuzzy rule-based auto-tuned internal model controller for real-time experimentation on temperature and level processes

Recently, internal model control (IMC) technique has been widely employed for various industrial close-loop control applications. Rewarding feature of IMC controller is that we need to tune only one parameter λ (close-loop time constant) for achieving the desired close-loop response. But, finding an appropriate value of λ is not an easy task. From the basic behaviour of IMC-based close-loop responses, it is found that when the process variable is moving very fast towards the desired value, relatively larger value of λ (smooth control) is required to reduce the possible oscillations. In contrary, smaller value of λ (tight control) is preferred when the process response is quickly moving away from the set point to restrict its further deviation. Hence, to mitigate the limitation of conventional IMC tuning with a fixed λ, a fuzzy rule-based auto-tuning scheme is proposed here for IMC-proportional integral derivative (IMC-PID) controller and its performance is validated through real-time experimentation on temperature and level control loops.

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.