Internal Model Control Structure Research Articles

Internal Model Control Structure Inspired Robotic Calligraphy System

Internal Model Control Structure Inspired Robotic Calligraphy System

INVERSE NEURO-FUZZY MODEL BASED CONTROLLER DESIGN FOR A PH NEUTRALIZATION PROCESS

Since pH neutralization processes have extremely nonlinear characteristics, controlling it might be difficult. Therefore, a special controller design is needed to handle the high nonlinearities of the process. In this study, an inverse neuro-fuzzy model-based controller (NFMBC) design is presented for control of a pH neutralization process (NP). Input-output (IO) data set of the process is collected by applying a proper excitation signal. Then, forward and inverse neuro-fuzzy models of the process are constructed by using this data set after a training process. In terms of design simplicity, a two-input-one-output model structure is chosen for both neuro-fuzzy models. These forward and inverse neuro-fuzzy models are used in a nonlinear internal model control (NIMC) structure in order to provide robustness against disturbances and model mismatches. To examine the proposed controller's performance, simulation studies are carried out under setpoint variation and disturbance conditions. Additionally, the performance of the inverse NFMBC is compared to that of a fuzzy proportional integral derivative (FPID) controller with a 7x7 rule base. The results demonstrate that the designed controller provides more effective control performance for setpoint variations and also exhibits higher robustness against disturbances in the acid flow rate than the FPID controller.

Tuning Parameter-free Model Predictive Control with Nonlinear Internal Model Control Structure for Vehicle Lateral Control

Tuning Parameter-free Model Predictive Control with Nonlinear Internal Model Control Structure for Vehicle Lateral Control

Adaptive Internal Model Control Based on Parameter Adaptation

In actual industrial control, many objects have the characteristics of large lag and time-varying parameters, which makes it difficult for traditional PID control to obtain satisfactory control effects. Therefore, engineers need a control algorithm with a better control effect and a simple structure, and thus the internal model control is introduced into industrial process control. Internal model control has received a lot of attention in the control field because of its excellent control effect, and in ideal conditions, it can perfectly suppress external disturbances, and the output strictly tracks the input. On the basis of the internal model control, a two-degrees-of-freedom internal model control was developed. Compared with the conventional feedback control, the internal model control structure mainly embeds an internal model consistent with the control object in the control object, so the deviation between the internal model and the control object determines the quality of the control effect. In this paper, the internal model is changed to an adjustable parameter model, and the model parameters are adjusted in real time using the parameter adaptive algorithm, so that the model output error is as small as possible, or even zero. In order to solve the influence of interference on the system, compensation based on MRAC theory is used. In order to verify the feasibility of the algorithm, it was applied to the landing process control of fixed-wing Unmanned aerial vehicle) UAV and achieved satisfactory results.

An internal model control method for wave rotor refrigeration process based on Harris hawks optimization

A novel internal model control (IMC) method for wave rotor refrigeration process (WRRP) based on Harris hawks optimization (HHO) is presented in this paper. Firstly, an identification model is established by the test data of the WRRP. In order to reduce the complexity of the model, the Routh order reduction method was used to reduce the order of the identification model. This procedure yields an approximate second order model with time delay for the WRRP. Secondly, an IMC method based on HHO is proposed after analyzing the time delay characteristics of the WRRP model. This method improves the traditional IMC structure, and introduces a three degree of freedom IMC structure. The parameters of the controller are optimized by HHO to make the comprehensive performance index of the system reach the best. Simulation results demonstrate that the proposed method can achieve a good performance of tracking and disturbance rejection.

Robust modified partial internal model control for stable, unstable and integrating processes

ABSTRACT For open-loop stable processes, the internal model control (IMC) provides a simple and effective parameterisation of stabilising controllers. However, for unstable processes, it cannot be directly used for control system implementation. In this paper, a new unified approach for the IMC design is proposed for stable, unstable and integrating processes, using the modified IMC (m-IMC) structure in which an additional controller is introduced along with the basic IMC. Also, the partial IMC (PIMC) concept is utilised, wherein we write the plant as the summation of stable and unstable parts and consider only the stable part as the internal model. The combined approach is thereby referred to as modified partial IMC (m-PIMC). This paper presents a graphical method to obtain controller parameters for the proposed m-PIMC to satisfy the given gain margin () and phase margin () specifications. Further, stability boundary and robust boundary for the controller parameters are obtained which respectively give a set of all controller parameters stabilising the close loop and a set of all controller parameters ensuring robust stability. Seven different well-known standard stable, unstable and integrating process models are considered for the proposed m-PIMC design, and simulation examples are given for four selected plant models.

Improved internal model control method for carbon content of argon–oxygen refining ferrochromium alloys

We propose an improved internal model control method for the carbon content in the production process of argon–oxygen refining ferrochromium alloys. In the actual process, the control output is restricted and cannot fully demonstrate the control effect. Therefore, by decomposing the traditional internal model controller, we achieved saturation compensation, overcoming this limitation. In addition, by referring to the current production process, the smelting stages with different carbon-content ranges were determined. Combined with the actual equipment conditions, an anti-saturation internal model controller structure and a controller saturation numerical expert system were constructed, forming a fully improved internal model control system. The proposed method fully utilizes the steady-state error-free characteristic of the internal model control, achieving the preset control goal and significantly shortening the smelting time and improving the smelting efficiency.

U-Model-Based Two-Degree-of-Freedom Internal Model Control of Nonlinear Dynamic Systems.

This paper proposes a U-Model-Based Two-Degree-of-Freedom Internal Model Control (UTDF-IMC) structure with strength in nonlinear dynamic inversion, and separation of tracking design and robustness design. This approach can effectively accommodate modeling error and disturbance while removing those widely used linearization techniques for nonlinear plants/processes. To assure the expansion and applications, it analyses the key properties associated with the UTDF-IMC. For initial benchmark testing, computational experiments are conducted using MATLAB/Simulink for two mismatched linear and nonlinear plants. Further tests consider an industrial system, in which the IMC of a Permanent Magnet Synchronous Motor (PMSM) is simulated to demonstrate the effectiveness of the design procedure for potential industrial applications.

Real-time application of IMC-PID-FO multi-loop controllers on the coupled tanks process

The coupled tanks process is a two input-two output system. It presents a nonlinear behavior and interactions characteristic. After the nonlinear model is obtained, it is linearized around an operating point. A fractional-order proportional–integral–derivative based on the internal model control paradigm (1DOF-IMC-PID-FO) multi-loop controller is determined without considering the interactions, and a fractional-order proportional–integral–derivative based on the 2-degree-of-freedom internal model control structure (2DOF-IMC-PID-FO) multi-loop controller is determined by considering the interactions. Thus, an interactions reduction effect controller is calculated. Both controllers are implemented on a real-time process using the Real Time Windows Target of MATLAB. The objective of the control is to maintain the water level in the lower tanks at desired values. In the experiment, setpoint tracking and disturbance rejection tests are carried out to assess the performance of both 1DOF and 2DOF-IMC-PID-FO multi-loop controllers.

Robust internal model controller with increased closed‐loop bandwidth for process control systems

This study proposes a modified internal model control (IMC) structure in which an additional controller is added to the standard IMC structure to improve the closed-loop system bandwidth. The resulting structure is evaluated to satisfy standard IMC objectives of nominal performance and robust stability. The novelty of the work is to design a fractional order (FO) filter in the IMC structure so that gain margin ( A m ) and phase margin ( ϕ m ) specifications could be independently satisfied for a first-order plus time delay (FOPTD) process control plant. The proposed modified IMC (m-IMC) is simulated for three different FOPTD systems to validate and substantiate the theoretical analysis. The proposed m-IMC is compared with different integer order as well as FO controllers. The transient performance are compared in terms of rise time ( T r ), settling time ( T s ), maximum overshoot (% M p ) and the effectiveness is measured in terms of integral square error. To validate the viability of the proposed control scheme, it is implemented on a laboratory DC servo-system.

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.

A novel grey decision-DE optimized internal model controller for vibration control of nonlinear uncertain aeroelastic blade system

In this paper, a novel grey decision-differential evolution (GD-DE) optimized internal model controller is proposed for the control of nonlinear aeroelastic blade system (ABS) under time-varying uncertainties and control saturations. Two-port internal model control structure is presented for saturation compensation. The filter parameter of the controller is optimally tuned by proposed GD-DE algorithm, which is designed based on the grey decision incidence theory and differential evolution algorithm. The superiority of GD-DE optimized tuning technique is verified, compared to conventional IMC tuning method and other evolutionary algorithm based techniques. The robustness is analysed by comprehensive simulations from time-invariant uncertainties to large periodic or random time-varying uncertainties. The realistic condition with input/output disturbances is also involved. Simulation results show that the proposed controller outperforms existing adaptive IMC controller and other advanced controllers with greatly improved dynamic performance, stronger robustness and better saturation compensation on various conditions.

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.

Simplified tuning of IMC based modified smith predictor for UFOPDT processes

Abstract A simplified tuning guideline for internal model control (IMC) based modified Smith predictor technique is reported here for unstable lag dominated first-order processes with dead time (UFOPDT). Pole location in right half section of s-plane signifies the unstable behaviour of UFOPDT processes. Mostly, chemical processes like isothermal chemical reactor, bioreactor, dimerization reactor, fluid catalytic cracker etc. are found to be lag dominated and unstable along with considerable time delay. Smith predictor technique based control methodology is considered to be a well-accepted approach for such cases. However, conventional Smith predictor technique is not capable enough for controlling UFOPDT processes. Whereas modified Smith predictor is found to be quite competent in such cases as its design involves more than one controller. Modified Smith predictor structure is capable to provide desirable closed loop response during set point tracking along with the load recovery phases. To mitigate the tuning complexity of multiple controllers involved in modified Smith predictor designing, suggested IMC structure employs single tuning parameter λ i.e. closed loop time constant for all three controllers concerned. Noticeable performance enhancement is reported by the proposed scheme as no overshoot is observed during set point tracking. Moreover, smooth and efficient load rejection behaviour is also obtained. Supremacy of the proposed tuning is established through closed loop performance comparison with others’ reported modified Smith predictor based tuning relations for chemical reactor and bioreactor in terms of performance indices as well as stability margins.

Design of a robust controller for DC/DC converter–electrolyzer systems supplied by [formula omitted]WECSs subject to highly fluctuating wind speed

A buck-based, isolated, high-voltage-ratio DC/DC converter that allows supplying a proton exchange membrane (PEM) electrolyzer from a micro-wind energy conversion system (μWECS) has been recently presented. It exhibits low ripple at the switching frequency on the output voltage and current and represents an attractive solution for low-cost hydrogen production. In this paper, a more accurate mathematical model of such a converter is derived and discussed. Then, a model-based robust controller is designed in the frequency domain using the Internal Model Control structure and in the context of H2∕H∞ optimal control. The controller satisfies the condition of robust stability and behavior, i.e., it guarantees stability and the desired behavior in the presence of parametric variations and unmodeled dynamics. In particular, the robustness in the presence of variations of DC-link voltage and buck input inductance is verified from the theoretical point of view. The validation of the controller is performed by integrating it into a detailed switching model of the DC/DC converter, which is implemented on a widely used circuit-oriented simulator. Good results are obtained in terms of dynamic and steady-state behavior, even in the presence of the above variations. A comparison is also carried out with the results obtained using an integral controller designed on the basis of the above mathematical model. Such a comparison shows the superiority of the robust controller over the integral controller in all the operating conditions, especially when the DC-link voltage is subject to significant variations and is affected by a non-negligible low-frequency ripple due to the presence of the diode rectifier at the output of the μWECS.

A Novel Design of Fractional PI/PID Controllers for Two-Input-Two-Output Processes

In this paper, a new formulation of fractional order proportional integral (PI)/ proportional integral derivative (PID) controller is proposed. The proposed controller will be justified for some well-known two-input-two-output (TITO) processes. In order to deal with interactions between process variables in a multivariable system, as well as multiple delay times in process transfer functions, the simplified decoupling Smith predictor (SDSP) structure is also used. The issue of decoupling realizability is solved by the PSO algorithm and fractional order processes are also suggested for model reduction. The tuning rules of the controller are derived in analytical terms based on the internal model control (IMC) structure. The effectiveness and robust stability of the proposed approach are illustrated by comparing it with other methods. To have a fair comparison, the robustness criterion using the M-Δ structure with μ-synthesis is adopted and the μ value of the proposed method is always kept smaller than the value of the others.

LMI Stability-Constrained Identification for Composite Adaptive Internal Model Control

Internal model control (IMC), which explicitly incorporates a plant model and a plant inverse model as its components, has an intuitive control structure and simple tuning procedure. Within the IMC structure, we propose composite adaptive IMC (CAIMC) which simultaneously identifies the plant and the plant inverse to minimize modeling errors and further reduce the tracking error. In this paper, the design procedure of CAIMC is generalized to an $n$ -th-order SISO plant. The main challenge in the generalization is to find an identification algorithm for an $n$ -th order system that satisfies the stability constraint, while assuring closed-loop stability. In the literature, stability-constrained identification has been formulated as a convex programming problem by re-parameterizing the constraint as a linear matrix inequality, but boundedness and continuity of the estimated parameters, which are critical for closed-loop stability of an adaptive control algorithm, are not guaranteed. We propose a modified stability-constrained identification method with established boundedness and continuity properties. Closed-loop stability and asymptotic performance of CAIMC are then established under proper conditions. The effectiveness of the proposed algorithm is demonstrated with an example.

ADRC-Based Current Control for Grid-Tied Inverters: Design, Analysis, and Verification

The conversion and utilization of renewable energy generations often require grid-tied inverters. When an LCL filter is applied to attenuate the high switching frequency harmonics, it is complex to design a controller with proper parameters due to the characteristics of the LCL filter and system uncertainties. In this article, with LCCL filter, the order of the inverter system is degraded from third order to first order, and an active disturbance rejection control-based current control strategy for LCCL -type grid-tied inverters is proposed. The proposed strategy is able to treat the unknown dynamics and the external disturbance of the inverter system as overall disturbance through a single structure, and the closed-loop system is regulated by an improved control law with reference differential feedforward. Moreover, with parameter uncertainties considered, the robustness of the proposed strategy is studied through an internal model control structure. A 2-kW experimental prototype has been tested to verify the effectiveness of the proposed scheme.

A New Approach of Data-Driven Controller Tuning Method By Using Virtual IMC Structure—Virtual Internal Model Tuning—

In this paper, we propose a new method for updating controllers by using closed loop data without a mathematical model of plant. The proposed method here requires only one-shot output data obtained in the closed loop experiment together with the feedback controller used in this initial experiment and the desired tracking transfer function. This method is derived based on the idea of the data-driven prediction and the concept of the internal model control (IMC) structure that only appears in the virtual closed loop system. Finally, the validity and the effectiveness of the proposed method are verified through experimental examples.

Comments on “Extensions and Performance/Robustness Tradeoffs of the EWMA Run-to-Run Controller by Using the Internal Model Control Structure”

Adivikolanu and Zafiriou proposed an RtR-internal model control scheme with some particular parameters and two tuning hyper-parameters for semiconductor manufacturing processes to completely and efficiently compensate against process shifts and drifts even in the presence of modeling error and metrology delay. In their scheme, these particular parameters are very important for further analyzing the robust stability and performance of the closed-loop system. However, it is found that the analytic expressions of these particular parameters and the consequent robust stability condition are not completely correct. In this paper, we derive the exact analytic expressions of these particular parameters and the corresponding robust stability condition.