Internal Model Control Technique Research Articles

Local DER Control with Reduced Loop Interactions in Active Distribution Networks

Active Distribution Networks are Multi-Input Multi-Output (MIMO) systems with coupled dynamics, which cause interactions among the control loops of Distributed Energy Resources (DERs). This undesired effect leads to performance degradation of voltage control. To mitigate the effects of this unavoidable coupling, the present paper proposes a systematic design procedure based on the analysis of the interaction’s sources. In detail, each DER is equipped with a double-loop PI to control the active and reactive power output of the voltage source converter, which connects the DER to the network’s node. Furthermore, to guarantee ancillary services, the two loops are coupled by a simple mechanism of cooperation of the active power to voltage regulation realized by a filtered droop law. To achieve voltage regulation with reduced loop interactions, the PI parameters and the filter’s pulse are designed according to a procedure with two sequential steps based on the Internal Model Control (IMC) technique. Simulation studies are finally presented to demonstrate that the proposed design method achieves both reduction of the loop interaction and robust voltage control in the presence of model parameter uncertainty in the MIMO plant, modeling various operating conditions of the ADN, including a step connection of large loads, renewable energy source variations, and changes in the substation transformer ratio.

Simple Internal Model-Based Robust Control Design for a Non-Minimum Phase Unmanned Aerial Vehicle

Robust control has been successful in enabling flight stability and performance for UAVs. This paper presents a simple explainable robust control design for UAV platforms with non-minimum phase (NMP) zero characteristics in their model. The paper contributes to economic (simple) robust control design by addressing the NMP model’s characteristics via Internal Model Control (IMC) and its impact on the UAV pitch response performance. The proposed design is compared with a Parallel Feedback Control Design (PFCD) scheme for the same vehicle platform, for fair comparison. Simulation results illustrate the achievement of the proposed control designs for the UAV platform; only the pitch control is addressed. A by-product of this work is the interpretation of different ways of manipulating the non-minimum phase plant model, so-called ‘modelling for control’, to enable the simple controller design. The work in this paper underpins the simplicity and robustness of the IMC technique for the NMP UAV platform, which further supports the explainability of the control structure relative to performance.

Extended Approach to Analytical Triangular Decoupling Internal Model Control of Square Stable Multivariable Systems With Delays and Right-Half-Plane Zeros

The Analytical Triangular Decoupling Internal Model Control (ATDIMC) technique for 2×2 systems is generalized to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> × <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> systems ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ≥2) with delays and right-half-plane (RHP) transmission zeros. The formulation is done by first creating a triangular closed-loop transfer function matrix corresponding to the achievement of the triangular decoupling objective of restraining inverse-response and control-loop-interaction characteristics to a single plant output. Subsequently, the corresponding multivariable internal model controller is calculated, with transfer-function approximations made using optimization algorithm that minimizes the Integral Time-Weighted Absolute Error (ITAE) of the difference between the step responses of the original and reduced expressions. It is shown that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ATDIMC designs emerge that achieve the shifting of inverse responses and interactions to a least-desired output, with delays retained for all outputs and asymptotic tracking of setpoints achieved for all <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> outputs of each design. To mitigate the possible effect of severe interaction on the least-desired output, a modification of this formulation is performed to spread inverse-response behavior to a second output, while minimizing the interaction of that output with the initial least-desired output. Simulation results for selected 3×3 and 4×4 systems show the effectiveness of these propositions.

Controller considerations for attenuating noise in process variables in presence of uncertainties in plant parameters

This paper analyzes the effect of uncertainties on noise amplification in the internal model control (IMC) and classical control design technique. It is observed that IMC based on integral absolute error (IAE) design criteria (IMC-IAE) boosts noise in the process variables, system output as well as in control input for certain class of systems. Moreover, the resulting control system becomes highly sensitive at high frequency with uncertainty in plant parameters which further boosts noise in process variables. Integral square error (ISE) based IMC (IMC-ISE) is, however, free from the issues of sensitivity and noise amplification at high frequencies and not analyzed in this paper. This issue also exists in well known classical controllers such as PID controller, lead, lag, lead-lag compensators, etc. The solution to this problem is to choose the controller such that the open loop transfer function (OLTF) and hence the closed loop transfer function (CLTF) are strictly proper, and a formal proof to this effect is laid down in this paper. Further, simulation study is carried out to show the impact of noise and the effect of plant uncertainty in output and control input for IMC-IAE control system. The proposed theory is validated experimentally on a DC servo system by comparing noise power of the control input for IMC-IAE and PID controllers.

Modified Smith predictor‐based P‐PD control for pure integrating delay dominated processes

AbstractModified Smith predictor (MSP) with P (proportional)‐PD (proportional‐derivative) control methodology is designed for pure integrating processes with time delay (IPTD). Industrial processes such as liquid supply to the large storage, fractional distillation, and superheated steam flow to turbine are found to be integrating in nature with dominant time delay. The proposed P‐PD control strategy ascertains the desired closed loop response. The closed loop time constant () is considered to be the sole tuning parameter for reducing the tuning intricacies of the proposed MSP‐based design. P controller in the forward path is tuned by the internal model control (IMC) technique towards enhanced servo tracking. In the feedback path, PD controller parameters are obtained from Routh's stability analysis for improving regulatory responses. Overshoot free set point response is observed and smooth as well as reasonably faster recovery is also found during load fluctuations. Effectiveness of the proposed MSP is validated during closed loop performance and stability analyses in comparison to others' reported dead time compensating methodologies.

On Internal Model Control (IMC) of MIMO Systems

Control of MIMO systems offers a challenging problem due to the cross coupling effects present between the inputs and the outputs of MIMO systems. In order to achieve an efficient control decouplers are introduced which eliminate these cross-coupling effects present in MIMO systems. With decouplers properly designed, it is possible to derive control inputs for fully-actuated and over-actuated MIMO systems to achieve reference tracking of the individual outputs. However, the reference tracking for individual outputs is almost unachievable in under-actuated MIMO systems with decoupling control methods. In dealing with this, the present work proposes an internal model control (IMC) applicable as appropriate to all classes of MIMO systems without incorporating any decoupling technique. This paper extends with two unique design methods of the IMC technique. These proposed methods enable one to attain perfect reference tracking of the individual outputs even in presence of the cross-coupling present in the MIMO systems. The conditions for the perfect reference tracking of multi outputs for under-actuated MIMO systems are derived. Different examples are considered to test the efficiency of the methods. The proposed methods are implemented on an experimental test set-up of highly non-linear and unstable cart-inverted pendulum system. The reference tracking goal and disturbance rejection capability of the control scheme are examined well in real-time. The experimental results are portrayed to establish the efficacy of the theoretical claim made.

Order Diminution of LTI Systems Using Modified Big Bang Big Crunch Algorithm and Pade Approximation with Fractional Order Controller Design

In this paper, a novel approach is proposed for the reduced order modelling of linear time invariant (LTI) systems. The proposed approach is a combination of modified Big bang big crunch (BBBC) optimization algorithm and Pade approximation technique. The beauty of the proposed approach is that the selection of solution space for BBBC algorithm is not entirely random, but structured via the use of Pade approximation approach. Hence, two principal criticisms of soft computing algorithms, i.e., random choice of solution space and larger simulation time are averted in the proposed technique. The proposed technique is substantiated via four different numerical examples from literature and compared with existing model order reduction (MOR) techniques. The concept of controller design is introduced via application of fractional order internal model control technique for load frequency control of power systems. Further, BBBC algorithm is employed to tune a boiler loop in power station. The results convey the efficiency and powerfulness of the proposed technique.

Experimental validation of fractional order internal model controller design on buck and boost converter

In this paper, fractional order internal model control technique is formulated for non-ideal dc–dc buck and boost converter. The fractional order internal model control approach integrates the concept of Commande Robuste d’Ordre Non Entier principle for tuning a fractional order filter with internal model control scheme. The final controller can be expressed as a series combination of proportional integral derivative controller and a fractional order low pass filter. To assess the robustness of the proposed fractional order internal model control scheme, both the servo response and regulatory response of the dc–dc converters are investigated in the presence of disturbances. The efficacy of fractional order internal model control technique is demonstrated via comparison with 2 degrees of freedom internal model control scheme. Furthermore, an experimental validation of fractional order internal model control is conducted on laboratory setup, and a dSPACE 1104 microcontroller is used for hardware implementation. The simulation results and the hardware validation are a testimony to the effectiveness of fractional order internal model control technique.

Improved Internal Model Control Technique for Position Control of AC Servo Motors

This paper focuses on the simulation analysis of the conventional Internal Model Control (IMC) technique and the development of two proposed control techniques for the position control of AC Servo Motor. Internal Model Control (IMC) technique [1] was only able to control the AC Servo Motor under static load condition. Also, it had step response problems, and it was not robust against external disturbances. For these reasons, the IMC technique was further improved to control the AC Servo Motor under dynamic load conditions by proposing Amended Internal Model Controller (AIMC). The step response and the robustness of AIMC against external disturbances were further improved by proposing AIMC+FLC. Where a Fuzzy Logic Controller (FLC) is designed and connected with the AIMC.

Control of Dynamic Positioning Ship Using Internal Model Control

Dynamic Positioning Ship System (DP) is an automated system, which is used to keep the ship maintain its position and heading at a fixed location or navigate along a predetermined track exclusively by mean of its own actives propulsions systems without using such fixing device as the anchor. DP system’s task is to control the ship moving at a fixed position or moves following the route for previous with low speed to execute a task. This paper presents a novel stability robustness controller for a dynamic positioning ship with uncertainties and unknown external disturbances. For the development and testing of the controller we present shematic diagram of DP systems, the mathematical modeling of the ship and the bias forces as slowly-varying environmental disturbances. The proposed controller has two loops. The inner loop uses an internal model control (IMC) technique to control the speed of the ship. The outer loop uses a propotional (P) control ler to control the position of the ship. The stability robustness of the control system is analysed. One of the key aspects of the prposed controller is that the robustness of the closed loop system can tuned via a single tuning parameter. The simulation results demonstrate that the proposed control system has high performance and robustness in the present of environment disturbance and uncertainty. The proposed control system was compared with PID control.The control algorithm of ship dynamic positioning is generally based on the classic PID, PID control has many advantages and has a strong robustness. However, the parameters of the PID control depend on the test will cost a lot of time and energy. Simulation results are provided to illustrate the effectiveness of the proposed controller. The problem of guidance and control of thruster actuators is out of scope of the paper.

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.

Analytical Triangular Decoupling Internal Model Control of a Class of Two-Input, Two-Output (TITO) Systems with Delays

The Decoupling Internal Model Control (DIMC) technique is modified to achieve triangular decoupling for a class of two-input, two-output systems with delays. The closed-loop transfer function matrix that guarantees stability and triangular decoupling within the IMC framework is mathematically developed, and the corresponding centralized decoupling internal model controller calculated for systems with delays and right-half-plane zeros. The shifting of inverse responses and interactions is achieved to a single least-desired output so that for non-minimum-phase (NMP) two-input, two-output (TITO) systems with delays, one output has some delay but has no interacting behaviour or inverse response behaviour, while the less-desired output has substantial interaction and inverse response behaviour, with asymptotic tracking of setpoints for both outputs. A simulation example shows the effectiveness of the proposed method.

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.

Optimal PID Controller Tuning using Simulated Annealing based Internal Model Control

In this paper, simulated annealing (SA), a heuristic algorithm is used to tune PID based Internal Model Control (IMC) for large and small / systems. PID tuning is effected with SA optimizer. The IMC technique requires tuning of a single parameter, filter constant which in turn is used to find the PID controller parameters: proportional gain, reset time and derivative time. The proposed method uses SA for tuning the filter constant. The proposed method is verified in systems with different / ratio.

Measurement and control of emergent phenomena emulated by resistive-capacitive networks, using fractional-order internal model control and external adaptive control

A fractional-order internal model control technique is applied to a three-dimensional resistive-capacitive network to enforce desired closed-loop dynamics of first order. In order to handle model mismatch issues resulting from the random allocation of the components within the network, the control law is augmented with a model-reference adaptive strategy in an external loop. By imposing a control law on the system to obey first order dynamics, a calibrated transient response is ensured. The methodology enables feedback control of complex systems with emergent responses and is robust in the presence of measurement noise or under conditions of poor model identification. Furthermore, it is also applicable to systems that exhibit higher order fractional dynamics. Examples of feedback-controlled transduction include cantilever positioning in atomic force microscopy or the control of complex de-excitation lifetimes encountered in many types of spectroscopies, e.g., nuclear magnetic, electron-spin, microwave, multiphoton fluorescence, Förster resonance, etc. The proposed solution should also find important applications in more complex electronic, microwave, and photonic lock-in problems. Finally, there are further applications across the broader measurement science and instrumentation community when designing complex feedback systems at the system level, e.g., ensuring the adaptive control of distributed physiological processes through the use of biomedical implants.

Modified IMC Technique for Nonlinear Uncertain Milling CNC Machine Tool System

The objective of this paper is to model a nonlinear computer numerical control machine tool (CNCMT) system for milling process. A modified internal model control (M-IMC) technique is proposed for position control of machine table. The study of milling process is mainly focused on the cutting mechanics and dynamics. The performance of CNCMT system is degraded due to the presence of disturbance like cutting force and parametric uncertainty. Considering the limitation of conventional internal model control (C-IMC) technique that is the poor performance under constant disturbance, an M-IMC technique is designed for the rejection of disturbance and position control of uncertain nonlinear CNCMT system. The performances of nonlinear uncertain CNCMT system using M-IMC technique is also compared with C-IMC and Ziegler–Nichols-tuned proportional–integral–derivative control techniques. The proposed M-IMC technique is designed to attain the better disturbance rejection capability, i.e., regulatory control with less control effort for the regulation of desired position of a machine table.

Load frequency control strategy via fractional-order controller and reduced-order modeling

This paper proposes a simple approach to design fractional-order (FO) controller via internal model control (IMC) technique for load frequency control (LFC) problem in power systems. The proposed scheme utilizes the concept of CRONE principle, model-order reduction and FO filter in IMC framework to derive a robust controller. Initially, the scheme is applied to single-area power system and then extended to two-area interconnected system. The turbines considered are non-reheated, reheated and hydro type; and physical constraints of turbine and governor are also taken into account to validate the applicability in more realistic environment. Simulation results show that it can bring improved disturbance rejection performance in nominal condition as well as in presence of uncertainties and constraints in plant parameters.

Process control performance evaluation in the case of variable set‐point with experimental applications

AbstractThe purpose of this paper is to contribute with some refinements to recent methods of analysis of control loop performance, based on the well‐established principle of Internal Model Control (IMC). Lower limits for the absolute value of the integral of control error (IAE) and the total variation of control action (TV) are assumed as reference values for a control considered good or at least acceptable. The overall performance index assumes as a benchmark a controller tuned according to rules of S(implified)IMC technique and is appropriately defined with respect to the lower limits of the two metrics IAE and TV. This allows the assessment of control loop performance, that is, the validity of tuning for PID‐type controllers in response to different types of reference change. In fact, one can assess performance in the case of set‐point changes as steps, ramps, or generic varying trends over time. In order to demonstrate the validity of the refined technique, several examples of simulation, case studies on a pilot plant, and real industrial data are presented.

Leader-following attitude consensus of multiple uncertain spacecraft systems subject to external disturbance

Summary The attitude consensus problem of multiple rigid spacecraft systems is one of the key issues in spacecraft formation flying and has been extensively studied. In this paper, we further consider the leader-following attitude consensus problem of multiple rigid uncertain spacecraft systems subject to a class of multi-tone sinusoidal disturbances with arbitrarily unknown amplitudes, initial phases, frequencies, and constant biases. In contrast to the existing results, in order to achieve asymptotic reference tracking and disturbance rejection by smooth control, we have integrated the distributed observer approach with internal model and adaptive control techniques. Simulation results are shown to validate the effectiveness of the proposed control law. Copyright © 2016 John Wiley & Sons, Ltd.

Multi-level cascaded DC/DC converters for PV applications

A robust multi-level cascaded DC/DC system for Photovoltaic (PV) application is advised in this article. There are three PV generators, each is coupled to a half-bridge buck cell. Each PV-generator–buck-converter channel is controlled such that maximum power is captured independently under different irradiation and temperature levels. The system operation under normal and abnormal conditions was comprehensively investigated. Internal Model Control (IMC) technique was adopted for tuning the controllers. An elaborate switching modulation strategy was used to reduce the current ripple and inductor size, while maintaining high efficiency. Annotative, simple and robust remedial strategies were proposed to mitigate different anticipated faults. Comprehensive simulation results in Matlab environment were illustrated for corroborating the performance of the advised cascaded DC/DC system under normal/abnormal conditions. The proposed system enjoys the merits of independency, reduced volumetric dimensions and improved efficiency. Furthermore, the system is inherently fault-tolerant.