Equivalent-input-disturbance Approach Research Articles

Disturbance rejection for switched singular systems using state decomposition technique and equivalent-input-disturbance with a dynamic state observer

In this study, an equivalent-input-disturbance (EID) method with a dynamic state observer and a state decomposition technique (SDT) are used to explore the disturbance rejection of a class of linear switched singular systems. The EID approach defines an EID signal, is defined for the control input channel and has the same impact on the system as exogenous disturbances. Additionally, it employs an observer to estimate the EID and achieves good disturbance-rejection performance. However, in the EID method, the coefficient matrix of the observer needs to be consistent with the coefficient matrix of the original system, which limits the application of the method. So, a dynamic state observer is designed to reconstruct the system state and estimate the disturbance in this study. Based on the state feedback control strategy, a disturbance-rejection control law containing disturbance information is designed and a closed-loop control system structure is established. Subsequently, the state equation of the closed-loop system is reorganised and decomposed into an algebraic equation and a differential equation using the SDT. Then, a Lyapunov function with few decision variables is designed to obtain an admissible criterion for the closed-loop system and the controller gains under arbitrary switching signals. Finally, the effectiveness of the presented method is verified via numerical simulations.

Equivalent Input Disturbance-Based Control: Analysis, Development, and Applications.

This article reviews the concept, analysis, development, and applications of the equivalent-input-disturbance (EID) approach. First, the definition and existence of the EID are given, and the configuration of the EID estimator is provided. Next, estimation errors in the conventional EID approach are explained, and error-suppression methods are exhibited, which improve the disturbance-rejection performance. Then, this article describes how to apply the EID approach and associate challenges in dealing with nonlinearities, time delays, and uncertainties. Moreover, this article reviews some additional meaningful studies that cannot be categorized into the above-mentioned classes. Finally, some conclusions and future directions are given. The EID approach has been successfully used to suppress the influences of exogenous disturbances, nonlinearities, time delays, and uncertainties in many control systems to improve control performance and robustness. Studies can further rich the theory of the EID approach in the future, such as designing evaluation index, improving disturbance-rejection performance, developing new applications, and combining with other control theory.

Parallel Operation Strategy of Inverters Based on an Improved Adaptive Droop Control and Equivalent Input Disturbance Approach

The operation of parallel inverters in microgrids is an important way to expand system capacity, but there are problems of circulating current fluctuations and power sharing errors in parallel inverters’ operation. In this paper, a parallel operation strategy for inverters based on improved adaptive droop control and Equivalent Input Disturbance (EID) is proposed. Firstly, the model and control topology of parallel inverters are presented. Secondly, in order to solve the power sharing error caused by impedance difference and the voltage drop caused by virtual impedance, a reference voltage generator based on improved adaptive droop control is proposed. Then, considering the circulating current fluctuation as a disturbance, a voltage controller based on an equivalent input disturbance approach is proposed to reduce the disturbance. Finally, simulation in MATLAB/Simulink is carried out to verify the effectiveness of the parallel operation strategy.

Generalized-Extended-State-Observer and Equivalent-Input-Disturbance Methods for Active Disturbance Rejection: Deep Observation and Comparison

Active disturbance-rejection methods are effective in estimating and rejecting disturbances in both transient and steady-state responses. This paper presents a deep observation on and a comparison between two of those methods: the generalized extended-state observer (GESO) and the equivalent input disturbance (EID) from assumptions, system configurations, stability conditions, system design, disturbance-rejection performance, and extensibility. A time-domain index is introduced to assess the disturbance-rejection performance. A detailed observation of disturbance-suppression mechanisms reveals the superiority of the EID approach over the GESO method. A comparison between these two methods shows that assumptions on disturbances are more practical and the adjustment of disturbance-rejection performance is easier for the EID approach than for the GESO method.

Preview repetitive learning control for islanded microgrids based on equivalent input disturbance approach

Due to the rapid drop in peak dc-link voltage (PDV) caused by environmental changes, as well as the majority of loads being naturally nonlinear, the output voltage of the microgrid inverters is always distorted. To boost the PDV at a low cost and reduce the total harmonic distortion (THD) of output voltage, a strategy is proposed in this paper to synchronously control ac- and dc-sides voltage. A double closed-loop PI controller is used to indirectly control the PDV of Z-source inverter (ZSI). Sinusoidal reference voltage generated by the primary power layer is merged to construct an augmented dynamic system, and an integrated optimal controller on the ac-side is obtained. Preview repetitive control (PRC) and error compensation can improve output voltage tracking accuracy. The state feedback component effectively suppresses the resonance of the filter, lowering the system’s sensitivity to parameter perturbation. Combined with this, the equivalent input disturbance (EID) is used to eliminate the potential interference in microgrids, which can shorten the recovery time of the system. Both simulations and experiments are provided to demonstrate the better performance of the proposed approach in comparison to other different repetitive controllers.

A Modified Disturbance-Rejection Approach in Networked Control Systems Based on Adaptive Model Predictive Control and Equivalent-Input-Disturbance

This paper presents an adaptive compensation control strategy for packet losses, time delays, and exogenous disturbances in a networked control system. The structure consists of five parts: a plant, a Luenberger observer, an equivalent-input-disturbance (EID) estimator, an adaptive model predictive controller (AMPC), and a network. The AMPC in the local main control room produces an adaptive tracking gain, which can ensure the effective tracking of the reference signal in the presence of uncertainty and time delays in the plant. The EID estimator at the local site compensates for packet losses and exogenous disturbances through an independently designed state observer and a low-pass filter. A practical application case results show the effectiveness of the presented method compared with the conventional EID approach.

Designing low-pass filter in equivalent-input-disturbance compensator for improving disturbance-rejection performance

This paper presents a high-order low-pass filter for the equivalent-input-disturbance (EID) approach to improving the disturbance-rejection performance. The configuration characteristic of the presented filter clearly explains the reason why the disturbance-rejection performance is improved and provides a guideline to design it. Using the presented filter to replace the conventional filter derives a high-order EID (HEID) approach. It is easy to apply the small-gain theorem in deriving stability conditions of the HEID-based control system. Moreover, the presented filter is proved to be better than the conventional one. Finally, a comparison shows the validity and superiority of the presented method. And a simulation result shows that the HEID approach is easily extended in a multiple-input, multiple-output system even with effects of a white noise and parameter uncertainties.

Disturbance rejection using SMC-based-equivalent-input-disturbance approach

This paper uses the sliding-mode control (SMC) to compensate for an estimation error caused by the filter in an equivalent-input-disturbance (EID) compensator. The application of the SMC brings another shortcoming: The chattering problem. To solve such a problem, this paper makes use the features of the EID approach and presents a method of designing a small switching gain based on the estimation error. Combining the SMC, the EID approach, and the switching-gain design law, this paper presents a new system configuration. The presented SMC-based-EID control system not only improves the disturbance-suppression performance of the EID approach but also solves the chattering problem in the SMC. A comparison shows the validity and superiority of our method. Furthermore, the robustness of the disturbance-rejection performance with respect to measurement noise is also shown by the example.

Disturbance estimator based dynamic compensator design for fractional order fuzzy control systems

The robust stabilization problem for singular fractional order time delay T-S fuzzy systems with nonlinearities and unknown external disturbances is addressed in this paper. An equivalent-input-disturbance (EID) estimator is used to estimate the impact of external disturbances and nonlinearities on the system output. Based on this EID approach, a dynamic compensator is designed to solve the stabilization problem of the considered system. Moreover, by considering a relevant Lyapunov-Krasovskii functional candidate and by using Lyapunov technique, the stability conditions in terms of LMIs are acquired for the considered closed-loop system. At last, to validate the effectiveness of the proposed result, two numerical examples are provided.

New spectra of responses and control force for design of equivalent-input-disturbance-based active structural control of base-isolated buildings

This paper presents new spectra of responses and control force for an active base-isolated building that uses the equivalent-input-disturbance (EID) approach for active structural control. The EID approach estimates the effect of disturbances and uses it to suppress building vibrations. This system plugs an EID estimator into a conventional state-feedback control system. Note that these kinds of disturbance-rejection systems contain both feedforward and feedback terms from disturbances to a control output. This paper describes spectra that can handle systems with such structure. The spectra can be used to simplify the design of an active structural control system. This paper illustrates the use of the spectra for control-system design and presents a design algorithm for the EID-based control system. A shear building model and 44 kinds of earthquake waves are used to demonstrate the availability of the spectra.

Demagnetization-Fault Reconstruction and Tolerant-Control for PMSM Using Improved SMO-Based Equivalent-Input-Disturbance Approach

A demagnetization fault not only degrades the performance of a permanent magnet synchronous motor (PMSM) drive system, but also may even cause the irreversible demagnetization. This article presents an improved-sliding-mode-observer (ISMO) based equivalent-input-disturbance (EID) method to reconstruct a demagnetization fault and to perform fault-tolerant control for the demagnetization fault in a PMSM drive system. The models of healthy and demagnetized PMSM are first established. Next, an ISMO is constructed by inserting a decoupling term. It completely removes the influence of the motor speed on the reconstruction of a demagnetization fault. Then, the ISMO-based EID approach is developed to reconstruct the fault with the high precision and maintain system control performance even for a demagnetization fault. The stability of the whole system is proved by using the concept of globally uniformly ultimately bounded. Finally, the validity of the method is demonstrated using hardware-in-the-loop simulation.

EID-based robust stabilization for delayed fractional-order nonlinear uncertain system with application in memristive neural networks

Abstract In this paper, the robust stabilization for fractional-order (FO) delayed nonlinear uncertain system with disturbance is obtained for the first time by using equivalent-input-disturbance (EID) with internal model. And the EID method is applied to FO memristive neural networks (FMNNS) as an application. The fractional-order state-feedback controller is designed, and the gains of controller can be derived by LMI. Three simulations are given, the comparison between EID approach with and without internal model is showed and the observer-based method is compared to emphasize the effectivity of internal model control. And the example for FMNNs and a simple practical example are given to show the accuracy of the proposed results.

Modified Equivalent-Input-Disturbance Approach to Improving Disturbance-Rejection Performance

This article presents a modified equivalent-input-disturbance (MEID) approach that actively rejects exogenous disturbances. A dynamic compensator is newly introduced in a conventional equivalent-input-disturbance (EID) estimator to further suppress the disturbances. The mechanism of the MEID approach to improving disturbance rejection is analyzed based on the transfer characteristic from the EID to the output of the system, and a stability condition of the MEID control system is presented and is used to design the parameters of the system. A comparison with the conventional EID approach and the disturbance-observer method through experiments demonstrates the validity of the presented method.

An improved equivalent-input-disturbance approach for PMSM drive with demagnetization fault

Closed-loop torque control system of permanent magnet synchronous motor (PMSM) drive is highly applied in industrial applications. However, high temperature and other external factors lead to permanent magnet (PM) demagnetization fault of the motor, which inevitably brings barriers to precise torque control. This paper presents a rejection method for demagnetization based on an improved equivalent-input-disturbance (EID) approach. A system model, which contains demagnetization fault, is first constructed. Then, an equivalent-input-demagnetization on the control input channel is used to describe the model. An improved EID approach is designed to reject the effect of the demagnetization fault. In particular, an improved sliding-mode observer rather than the Luenberger observer in a conventional EID theory is designed to estimate the equivalent-input-demagnetization. This greatly enhances the response speed and accuracy of the estimation and rejection, and then effectively improves the accuracy of torque tracking. Finally, the step change and the ramp change of a demagnetization are introduced into a hardware-in-the-loop experiment, separately. Comparisons with other methods show the effectiveness of the method.

Robust Current Predictive Control-Based Equivalent Input Disturbance Approach for PMSM Drive

The implementation and experimental validation of current control strategy based on predictive control and equivalent input disturbance approach is discussed for permanent magnet synchronous motor (PMSM) control system in the paper. First, to realize the current decoupling control, the deadbeat predictive current control technique is adopted in the current loop of PMSM. Indeed, it is well known that the traditional deadbeat current control cannot completely reject the disturbance and realize the zero error current tracking control. Then, according to the model uncertainties and the parameter variations in the motor, an equivalent input disturbance approach is introduced to estimate the lump disturbance in the system, which will be used in the feed-forward compensation. Thus, a compound current controller is designed, and the proposed algorithm reduces the tracking error caused by the disturbance; the robustness of the drive system is improved effectively. Finally, simulation and experiment are accomplished on the control prototype, and the results show the effectiveness of the proposed current control algorithm.

Disturbance Rejection and Control System Design Using Improved Equivalent Input Disturbance Approach

This paper presents an improved equivalent input disturbance (EID) approach to deal with exogenous disturbances and system nonlinearities. The disturbances and nonlinearities are regarded as a lumped disturbance on the control input channel. The EID approach, which has a state observer and an EID estimator, is used to estimate the lumped disturbance. There is a constraint between the observer and the estimator on the design of the control system for the conventional EID approach. A stable zero was added to the estimator to remove the constraint and to improve the stability of the system in this paper. This ensures that the observer and the estimator can be designed independently. An analysis of the improved EID approach explains the mechanism of disturbance rejection. The simulation and experimental results of position control of a ball-and-beam system demonstrate the validity of the method.

Motion Control of a Wheeled Inverted Pendulum Using Equivalent-Input-Disturbance Approach

This paper presents a new method for controlling the motion of a wheeled inverted pendulum (WIP) based on the equivalent-input-disturbance (EID) approach. Coordinate transformation first transforms the WIP into a simple nonlinear system divided into linear and nonlinear parts. The nonlinear part is then treated as a state-and-input-dependent disturbance, and the EID approach is used to estimate and compensate it. Simulation results of an NXTway-GS demonstrate the validity of the method.

Compensation in Repetitive Control System for Aperiodic Disturbances and Input Dead Zone

This paper extends the equivalent-input-disturbance (EID) approach to deal with the problem of aperiodic disturbance rejection for a plant with an input dead zone in a repetitive-control system so as to improve control performance for the tracking of a periodic signal. Since a dead zone greatly degrades control performance, we apply the EID approach to design a compensator for the nonlinearity by treating it as an input-dependent disturbance. An EID estimator is constructed by making the best use of a full-order generalized state observer (GSO). And a method of designing the GSO is explained. The EID estimate, which exhibits the synthetic effect of the nonlinearity and the aperiodic disturbance, is incorporated into a repetitive control law to compensate for the nonlinearity and the aperiodic disturbance. This method does not require any information about the dead zone. It guarantees perfect tracking for periodic reference input and satisfactory compensation of input dead zone and aperiodic disturbance at the same time. Simulation results demonstrate the effectiveness of this method.

An EID-based Fault Diagnosis Method for the Distribution Feeder with PV Generation Embedded

This paper describes a new fault diagnosis method based on an equivalent-input-disturbance (EID) approach for distribution feeder with photovoltaics (PV) generation embedded. In this method, the faults are regarded as disturbances of system, which can be estimated by EID approach. Through analyzing the characteristics of the EID, the faults position can be located and the fault types can be identified. Firstly, a dynamic model of distribution feeder for fault diagnosis is built. Next, an EID estimator is designed. Finally, the simulation results demonstrate the effectiveness of the method.

Global stabilization of 2-DOF underactuated mechanical systems—an equivalent-input-disturbance approach

This paper presents a new method of globally stabilizing a non-linear underactuated mechanical system with two degrees of freedom (DOF). It is based on the idea of equivalent input disturbance (EID), and designing the controller requires only the state variables of position, not velocity. The design procedure has two steps: (1) Use a global homeomorphic coordinate transformation to convert the original system into a new non-linear system. This changes the problem of stabilizing the original system into one of stabilizing the new system. (2) Divide the new system into linear and non-linear parts and take the non-linear part to be an artificial disturbance, thereby enabling use of the EID approach to globally asymptotically stabilize the new system at the origin. The new method was tested through numerical simulations on three well-known 2-DOF underactuated mechanical systems (TORA, beam ball, inertia wheel pendulum). The results demonstrate its validity and its superiority over others.