Integral Sliding Mode Control Approach Research Articles

Decentralized observer‐based integral sliding mode control design of large‐scale interconnected systems and its application to doubly fed induction generator‐based wind farm model

SummaryThis paper presents the design of a decentralized observer‐based control scheme for large‐scale interconnected systems based on the integral sliding mode control (ISMC) approach. To do this, a novel decentralized observer is designed via the ISMC approach that helps to estimate the unmeasured states. Then, by constructing a suitable Lyapunov function, sufficient conditions are derived in terms of matrix inequality, which guarantees the asymptotic stability of the interconnected system and the ultimate boundedness of estimation errors under external disturbances. An interconnected power system (IPS) integrated with a doubly fed induction generator (DFIG)‐based wind farm model is provided as a direct application. Theoretical conditions are validated through numerical simulations, in this regard, a well‐structured model of IPS with a DFIG‐based wind farm is introduced. From the simulation results, it is proven that the proposed decentralized observer‐based ISMC can provide a better estimation of the internal states in two area IPS with DFIG‐based wind farm.

Nonsingular Fixed-Time Tracking Guidance for Mars Aerocapture With Neural Compensation

Mars aerocapture is one of the most concerned technologies for future Mars sample-return and manned exploration missions. This article investigates the challenging problem of the reference trajectory tracking guidance for Mars aerocapture under uncertainties. Based on an integral sliding surface, a fixed-time neural adaptive tracking guidance law is synthesized by incorporating the neural network (NN) approximation into the fixed-time integral sliding mode control approach. Benefiting from the integral sliding surface design, the proposed tracking guidance law has no singularity problem inherently existing in terminal sliding mode control. By adopting the NN approximation to compensate for the lumped uncertain term in the feedforward loop, the proposed tracking guidance law is strongly robust against aerodynamic coefficient uncertainties and atmospheric density uncertainty. Stability analysis shows that the radial distance tracking error and its time derivative can stabilize to the small neighborhoods around the origin in fixed time under the proposed tracking guidance law. Finally, the effectiveness and advantages of the proposed tracking guidance law are illustrated through simulations and comparisons.

Adaptive integral sliding mode controller for solid state transformer based on generalized averaged model and T‐S fuzzy method

The integrated converter between distributed renewable source and main grid has been widely applied. Although the independent control strategies regarding each submodule of solid state transformer (SST) have been studied, the integrated control based on overall model has not been proposed. To this end, this paper proposes an adaptive integral sliding mode control strategy based on T-S fuzzy method for the single-phase SST to regulate the output voltage and guide the power transmission. First, the overall state-space model based on generalized average method is first built through quasi-Fourier series. It can capture switching ripple compared with conventional model. Furthermore, the built model with uncertainties and nonlinear components is switched as the linear time invariant system through T-S fuzzy method. Meanwhile, the system order can also be reduced, which reduces the complexity of the controller design. Based on this model, an integral sliding mode control approach with rapid dynamic response and strong robustness against perturbations or model uncertainties is proposed. Finally, several simulation and experimental results are provided to validate the performance of the proposed control approach.

Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization

This article proposes a novel fault-tolerant controller for a double-rod electro-hydraulic actuator whilst the motion control system faces with system disturbances/uncertainties and internal leakage fault. Firstly, taking the advantage of the coordinate transformation, the nonlinear system is converted to a linear system to apply the control design tools in linear control theory. Besides, the matched, mismatched disturbances, and internal leakage fault are integrated into a new lumped uncertainty based on this transformation. Inspired by the great capability of time delay estimation technique, the suggested controller is developed to effectively detect and compensate for the internal leakage fault. To enhance the performance of the control system, an adaptive integral sliding mode control approach is deployed to effectively suppress the lump estimated error, and the effects of fault. The perfect combination of input-output feedback linearization, adaptive integral sliding mode, and time delay estimation is investigated to achieve high-precision tracking control and strong robustness in the presence of matched, mismatched disturbances, and faults, simultaneously. Moreover, the global stability of the suggested control algorithm is demonstrated by the Lyapunov theory. Finally, several tracking performance comparisons of the proposed approach with the existing controllers to demonstrate the efficiency are exhibited through simulation analyses and experiment results.

Integral sliding mode control for back‐to‐back converter of DFIG wind turbine system

In this study, an integral sliding mode control approach for controlling the power electronics converters of a doubly-fed induction generator (DFIG) wind turbine system is presented. The power electronics interface consists of back-to-back converters. The rotor side converter regulates the active and reactive powers at the DFIG stator through controlling the stator currents. The stator current dynamics, with respect to the rotor voltages, is developed from the conventional equations of the DFIG model. In this control configuration, the knowledge about the rotor currents is not required, which reduces the use of the current measurement sensors. The grid side converter ensures constant dc-link voltage while transferring the power from the DFIG rotor to the grid. The proposed control approach uses a composition of sliding mode and integral parts to improve the overall performance and robustness against parametric variations and uncertainties. A lab-scale DFIG wind turbine system is used to investigate the proposed control approach efficiency under various operating conditions. The experimental results show the effectiveness of the proposed control approach in achieving control objectives to operate the DFIG wind turbine system.

Design of a chattering‐free integral terminal sliding mode approach for DFIG‐based wind energy systems

SummaryThis article proposes a Fuzzy Second Order Integral Terminal Sliding Mode (FSOITSM) control approach for DFIG‐based wind turbines subject to grid faults and parameter variations. Since traditional terminal sliding mode control (SMC) suffers from singularity, a novel integral terminal sliding manifold is proposed to eliminate chattering and improve the wind turbine's performance in the presence of faults and disturbances. A fuzzy system is proposed to auto‐tune the controllers' gains and ensures the invariance of the sliding surfaces even under heavy uncertainties, thus further improving the reliability and performance of the proposed controller. The performance of the proposed approach was assessed under various operating conditions. A comparison analysis with a standard SMC approach as well as the state of the art in voltage sag mitigation was also carried over. Reliability, robustness, and power availability under faulty grid conditions are among the main features of the proposed approach. In addition, the proposed approach exhibited chattering free dynamics and enabled the finite time convergence of the sliding manifold and overcame the singularity problem associated with standard TSMC.

Disturbance observer based adaptive sliding mode control for power tracking of PWRs

It is well known that the model of nuclear reactors features natural nonlinearity, and variable parameters during power tracking operation. In this paper, a disturbance observer-based adaptive sliding mode control (DOB-ASMC) strategy is proposed for power tracking of the pressurized-water reactor (PWR) in the presence of lumped disturbances. The nuclear reactor model is firstly established based on point-reactor kinetics equations with six delayed neutron groups. Then, a new sliding mode disturbance observer is designed to estimate the lumped disturbance, and its stability is discussed. On the basis of the developed DOB, an adaptive sliding mode control scheme is proposed, which is a combination of backstepping technique and integral sliding mode control approach. In addition, an adaptive law is introduced to enhance the robustness of a PWR with disturbances. The asymptotic stability of the overall control system is verified by Lyapunov stability theory. Simulation results are provided to demonstrate that the proposed DOB-ASMC strategy has better power tracking performance than conventional sliding mode controller and PID control method as well as conventional backstepping controller.

Robust adaptive neuronal controller for exoskeletons with sliding-mode

A robust neural adaptive integral sliding mode control approach is proposed in the present paper for nonlinear exoskeleton systems. The proposed control technique is composed of two parts: an adaptive neural network controller and an adaptive integral terminal sliding mode controller. The adaptive laws are developed to estimate unknown parameters and ensure asymptotic stability of the closed-loop system. Only classical system’s properties are supposed to be known, such as the bounds on some parameters. The unknown dynamics of the system are estimated on line by the neural network control part. The proposed adaptive control strategy is designed to ensure the reaching of the sliding surface with enhanced tracking performance. The singularity problem of the terminal sliding mode approach is overcomed without adding any constraint. The closed-loop stability of the system in the sense of Lyapunov is demonstrated. The effectiveness of the proposed approach is tested in real time application with healthy human subjects by performing passive arm movements using a 2-DOF upper limb exoskeleton.

Generalized Extended State Observer Based Integral Sliding Mode Control for a Nuclear Reactor System with Mismatched Uncertainties

This paper presents a generalized extended state observer based-integral sliding mode control for a nuclear reactor system subject to mismatched uncertainties. A generalized extended state observer is introduced to estimate system states as well as the mismatched uncertainties, which is then used to design an integral sliding mode control to eliminate the effect of unknown mismatched uncertainties. Stability of the proposed controller is proved by defining a Lyapunov function. Performance of the proposed control scheme is compared with the conventional integral sliding mode control. Simulation results exhibit that the proposed control scheme has better disturbance rejection ability compared to the conventional integral sliding mode control approach.

Neural Integral Non-Singular Fast Terminal Synchronous Sliding Mode Control for Uncertain 3-DOF Parallel Robotic Manipulators

Robotics have been substituting humans increasingly and effectively to operate repeated, dangerous, heavy, complicated works in human life, production industry, and discovery missions. This work designs a Neural Integral Non-singular Fast Terminal Synchronous Sliding Mode Control (NINFTSSMC) approach for 3-DOF parallel robotic manipulators with uncertain dynamics, using synchronous nonlinear sliding surface, where this sliding surface is formed through the integration of the Synchronization Control (SC) and the Integral Non-singular Fast Terminal Sliding Mode Control (INFTSMC). Accordingly, position errors and synchronization errors quickly converge to the sliding surface at the same time. Next, a Feed-Forward Neural Network (FNN) is applied to estimate uncertain dynamics, whose novelty, compared to a classic FNN, is that they utilize a Non-singular Fast Terminal Sliding Mode (NFTSM) error filter to replace a classic error filter. Thanks to this procedure, the lumped uncertain dynamics are compensated more quickly and more accurately, thus, the malfunction in the reaching phase of state variables approaching the sliding surface is handled thoroughly. Finally, the control approach is designed for a robotic system to achieve the prescribed performance, obtaining rapid error convergence, robustness with uncertain dynamics, minimum chattering, synchronization, and high precision. The stability of the control loop is secured according to the Lyapunov theory. To test the robustness and confirm the effectiveness of the suggested controller for a 3-DOF parallel manipulator, computer simulations and performance comparisons are conducted.

Discrete-Time Fractional Order Integral Sliding Mode Control of an Antagonistic Actuator Driven by Pneumatic Artificial Muscles

Recently, pneumatic artificial muscles (PAMs), a lightweight and high-compliant actuator, have been increasingly used in assistive rehabilitation robots. PAM-based applications must overcome two inherent drawbacks. The first is the nonlinearity due to the compressibility of the air, and the second is the hysteresis due to its geometric construction. Because of these drawbacks, it is difficult to construct not only an accurate mathematical model but also a high-performance control scheme. In this paper, the discrete-time fractional order integral sliding mode control approach is investigated to deal with the drawbacks of PAMs. First, a discrete-time second order plus dead time mathematical model is chosen to approximate the characteristics of PAMs in the antagonistic configuration. Then, the fractional order integral sliding mode control approach is employed together with a disturbance observer to improve the trajectory tracking performance. The effectiveness of the proposed control method is verified in multi-scenario experiments using a physical actuator.

Synchronization of two nonidentical complex-valued neural networks with leakage delay and time-varying delays

This paper investigates the global asymptotical synchronization of two nonidentical complex-valued neural networks (CVNNs) with leakage delay and time-varying delays via integral sliding mode control approach. A suitable sliding surface and an appropriate Lyapunov–Krasovskii functional are constructed. By using free-weighting matrix method combined with inequality technique, a sliding mode controller is designed to ensure the synchronization for the considered CVNNs. The obtained criterion is presented in the form of complex-valued linear matrix inequalities (LMIs), which could be calculated through YALMIP with solver of SDPT3 in MATLAB. An example is provided to demonstrate the obtained theoretical result.

Glucose–insulin stabilization in type-1 diabetic patient: A uniform exact differentiator–based robust integral sliding mode control approach

Diabetes mellitus is a persistent metabolic syndrome caused by impaired capability of the body’s production and usage of insulin. This impaired capability results in chronic hyperglycaemia, the elevated glucose concentration in the bloodstream, which may lead to many incurable complications. To escape this dire situation, a proper model-based exogenous infusion of insulin bolus is required, which is usually established via different feedback control strategies. In this article, the authors present a mathematical model–based robust integral sliding mode control approach for stabilization of internal glucose–insulin regulatory system in type-1 diabetic patient. Since the state variables of the system are not directly available to the controller, a uniform exact differentiator observer is employed to accomplish the aforementioned task. In the proposed control law, the incorporation of integral term in the switching manifold eliminates the reaching phase, which causes the sliding mode to establish from the very initial point, thus enhances the robustness property of the proposed control scheme. Moreover, the chattering problem is also substantially suppressed to a considerable extent along a defined manifold. To verify the theoretical analysis, the proposed control law is verified via computer simulations which demonstrate the effectiveness of the proposed control law against the external perturbations, that is, unannounced meal intake and physical exercise.

Observer-Based Fuzzy Integral Sliding Mode Control For Nonlinear Descriptor Systems

This paper investigates observer-based stabilization for nonlinear descriptor systems using a fuzzy integral sliding mode control approach. Observer-based integral sliding mode control strategies for the Takagi–Sugeno (T–S) fuzzy descriptor systems are developed. A two-step design approach is first developed to obtain the observer gains and coefficients in the switching function using linear matrix inequalities (LMIs), and the results are used to facilitate the development of a single-step design approach, which is seen to be convenient but introduces some conservatism in the design. The potential application to a class of mechanical systems is also considered. Since the descriptor system representation of mechanical systems is adopted, it is shown that in contrast to the existing fuzzy sliding mode control methods based on the normal system representation, the resulting T-S fuzzy system does not contain different input matrices for each local subsystem and the required number of fuzzy rules is consequently markedly reduced. Finally, the balancing problem of a pendulum on a car is numerically simulated to demonstrate the effectiveness of the proposed method.

Fuzzy Gains-Scheduling of an Integral Sliding Mode Controller for a Quadrotor Unmanned Aerial Vehicle

This paper investigates an Adaptive Fuzzy Gains-Scheduling Integral Sliding Mode Controller (AFGS-ISMC) design approach to deal with the attitude and altitude stabilization problem of an Unmanned Aerial Vehicles (UAV) precisely of a quadrotor. The Integral Sliding Mode Control (ISMC) seems to be an adequate control tool to remedy this problem. The selection of the controller parameters is done most of the time using repetitive trials-errors based methods. This method is not completely reliable and becomes a time-consuming and difficult task. Here we propose the tuning and selection of all ISMC gains adaptively according to a fuzzy supervisor. The sliding surface and its differential are declared as Fuzzy Logic Supervisor (FLS) inputs and the integral sliding mode control gains as the FLS outputs. The proposed fuzzy-based supervision mechanisms modify all ISMC gains to be time-varying and further enhance the performance and robustness of the obtained adaptive nonlinear controllers against uncertainties and external disturbances. The proposed adaptive fuzzy technique increases the effectiveness of the ISMC structure compared to the classical SMC strategy and excludes the dull and repetitive trials-errors process for its design and tuning. Various simulations have been carried out and followed by comparison and discussion of the results in order to prove the superiority of the suggested fuzzy gains-scheduled ISMC approach for the quadrotor attitude and altitude flight stabilization.

Reduced-Order Averaged Model and Non-Linear Control of a Dual Active Bridge DC-DC Converter for Aerospace Applications

The paper presents a generalized averaged model and a reduced-order averaged model of a dual active bridge bidirectional dc-dc converter, taking into account parasitic components. On the basis of these models, a particular non-linear voltage control scheme is suggested using an integral sliding mode control approach for driving the adopted single phase shift modulation technique. The main operative conditions of the converter have been examined through extensive simulations. The numerical results confirm the effectiveness of the proposed strategy. The suggested control exhibits a strong robustness against parameters variations and disturbances and presents a very simple implementation.

Robust Generation of Self-Oscillation in Pendulum Systems: A switched Integral Sliding Mode Control Approach

A two relay controller is robustified by a switched integral sliding mode controller in order to generate robust self-oscillations for pendulum systems. The proposed strategy assures theoretically exact robustification of the self-oscillations preserving the amplitude and frequency of the oscillations even in the presence of matched uncertainties/perturbations. The efficiency of the proposed robustifying approach is illustrated on an example of a Furuta pendulum.

Adaptive Integral Sliding Mode Control via Fuzzy Logic for Variable Speed Wind Turbines

[abstFig src='/00280006/16.jpg' width='300' text='Schematic of a wind turbine' ] Concerning variable speed wind turbines, this study suggests a control scheme that combines integral sliding mode control (I-SMC) and fuzzy logic. The control task is to maintain the output power at the rated value for variable operating points. Wind turbines suffer from serious nonlinearities that challenge the control task. To attack the issue, the nonlinear turbine model is linearized at some typical operating points. Then, pitch-angle and generator-torque controllers based on the linearized turbine models are formulated by the I-SMC approach. Meanwhile, a fuzzy inference system is designed to weight those controllers. Not only the scheme can stabilize nonlinear wind turbines, but also the control system is robust to resist wind-speed variations. Some results are presented to show the performance of the control scheme.

An LMI approach for the Integral Sliding Mode and H∞ State Feedback Control Problem

This paper deals with the state feedback control problem for linear uncertain systems subject to both matched and unmatched perturbations. The proposed control law is based on an the Integral Sliding Mode Control (ISMC) approach to tackle matched perturbations as well as the H∞ paradigm for robustness against unmatched perturbations. The proposed method also parallels the work presented in [1] which addressed the same problem and proposed a solution involving an Algebraic Riccati Equation (ARE)-based formulation. The contribution of this paper is concerned by the establishment of a Linear Matrix Inequality (LMI)-based solution which offers the possibility to consider other types of constraints such as \U0001d4d3-stability constraints (pole assignment-like constraints). The proposed methodology is applied to a pilot three-tank system and experiment results illustrate the feasibility. Note that only a few real experiments have been rarely considered using SMC in the past. This is due to the high energetic behaviour of the control signal.It is important to outline that the paper does not aim at proposing a LMI formulation of an ARE. This is done since 1971 [2] and further discussed in [3] where the link between AREs and ARIs (algebraic Riccati inequality) is established for the H∞ control problem. The main contribution of this paper is to establish the adequate LMI-based methodology (changes of matrix variables) so that the ARE that corresponds to the particular structure of the mixed ISMC/H∞ structure proposed by [1] can be re-formulated within the LMI paradigm.

An integral sliding mode control approach to observer-based stabilization of stochastic Itô descriptor systems

This paper is concerned with sliding mode observer design and observer-based sliding mode controller synthesis for stochastic Itô descriptor systems. A novel integral sliding surface, which involves a product of sliding variable and a negative definite matrix, is constructed for the error system. It is shown that the product term not only has a stabilizing effect on the sliding variable, but also is beneficial to remove a restrictive assumption often employed in the sliding mode control for stochastic Itô systems. Observer-based sliding mode controllers are designed to ensure the retainability of sliding surfaces from the beginning almost surely, and the asymptotically mean square admissibility of resultant sliding motion can be determined by solving a linear matrix inequality (LMI). Two examples are performed to check the theoretical findings.