Extended State Observer-based Control Research Articles

An Anti-Disturbance Extended State Observer-Based Control of a PMa-SynRM for Fast Dynamic Response

The control system of PMa-SynRMs (Permanent Magnet-assisted Synchronous Reluctance Machines) exhibit susceptibility to external disturbances, thereby emphasizing the utmost significance of employing an observer to effectively observe and suppress system disturbances. Meanwhile, disturbances in load are sensitive to control system noise, which may be introduced from current sensors, hardware circuit board systems, sensor-less control, and analog position sensors. To tackle these problems, this paper proposes an A-DESO (anti-disturbance extended state observer) to improve the dynamic performance, noise suppression, and robustness of PMa-SynRMs in both the constant torque and FW (flux weakening) regions. With the proposed A-DESO, lumped disturbance in torque could be detected, and speed could be extracted in position with unmeasurable noise. Thanks to the merits of the small observation error in the low-frequency region and the excellent anti-disturbance performance in the high-frequency region of the proposed A-DESO, the control of the PMa-SynRM features the advantages of a fast response and good noise immunity ability within the same observation error range. The proposed A-DESO presents a shorter convergence time and a better noise suppression ability, which leads to a better dynamic response of the PMa-SynRM when encountering an unknown load disturbance compared to the traditional ESO-based control, according to simulations and experiments.

A novel fuzzy extended state observer-based control for electro-optical tracking system with disturbances and measurement noises: Design, analysis and experiments

In the electro-optical tracking system (ETS), the stability of line-of-sight (LOS) is usually limited by low and medium-frequency disturbances and measurement noises. Conventionally, the active disturbance rejection control (ADRC) strategy is an effective method to improve the stability of LOS; however, it is limited by the fixed observer bandwidth, which is the parameter of the extended state observer (ESO). Besides that, for conventional ESO, the conflict exists between disturbance rejection ability and noise attenuation ability. In this paper, this problem is tackled by transforming the ESO which is the core element of ADRC, into a novel fuzzy self-tuning observer structure. The proposed method is experimentally validated to effectively ensure the stability of the LOS after obtaining an optimal trade-off between disturbance rejection ability and noise attenuation ability.

Robustly String Stable Longitudinal Control for Vehicle Platoons Under Communication Failures: A Generalized Extended State Observer-Based Control Approach

This paper investigates the longitudinal control of vehicle platoons with a focus on external disturbances, parameter uncertainties, and communication failures. When vehicle platoons encounter vehicle to vehicle wireless communication failures, the preceding vehicle’s acceleration is unavailable, which degrades the performance of the system. However, the existing achievements can not be directly used to address the aforementioned three issues. To this end, a generalized extended state observer-based control (GESOBC) law is contrived. First, the parameter uncertainties and the external disturbances are together regarded as a lumped disturbance. Then, a generalized extended state observer is designed to estimate the lumped disturbance and the preceding vehicle’s acceleration, separately. Based on the estimation, a composite controller consisting of a state feedback control part and an estimation-based feedforward control part is developed. Furthermore, it is proved that the proposed GESOBC method can guarantee the exponentially bounded stability of the individual vehicle and the input to state string stability of the whole vehicle platoon. Finally, numerical simulations are conducted to demonstrate the effectiveness and feasibility of the proposed method.

Optimal extended state observer based control for vibration reduction on a flexible cantilever beam with using air thrust actuator

The idea of using air thrusts for vibration control of structures has gained attention since the 1990s. However, only discontinuous controllers and switching functions have been studied with these actuators. Therefore, the main motivation of this study is to investigate air thrusters with continuous control methods for vibration reduction on a flexible cantilever beam. First, the finite element model of the flexible cantilever beam is defined. The order of the model is reduced according to the effective mass participation factor using the mode displacement method to obtain a controllable and observable system. The fundamental dynamics of the air thrust actuator, such as time constant, delay time and bandwidth, have been determined by system identification and considered in the control system. In this study, optimal extended state observer-based control (optimal ESOBC) tuned by optimal control law and particle swarm optimization (PSO) is proposed and compared to linear quadratic Gaussian (LQG) and positive position feedback (PPF) controllers. The performance of the controllers has been evaluated under several experiments such as initial displacement, impulsive disturbance, structure uncertainty and actuator uncertainty. The effectiveness of the controllers is determined by the RMS value of the beam displacement and the total air consumption. The results show that the ESOBC controlled air thrust actuator has suppressed beam vibrations more successfully than LQG and PPF controllers. In addition, the proposed method is found to be effective for low-frequency vibration suppression on flexible structures.

Applicability analysis of extended state observer-based control for systems subject to parametric disturbances

This paper discusses the applicability of Extended State Observer (ESO)-based control when systems are subjected to different types of parametric disturbances. The applicability is analyzed by establishing the characteristic polynomial of the closed-loop system. It is found that High-Bandwidth ESO-based control is beneficial to the elimination of state-parameter disturbances, but it has a negative impact on the elimination of input-parameter disturbances. In spite of this, the ESO-based control with suitable bandwidth can still be applied to systems which are subject to input-parameter disturbances. A Full-Order ESO-based control scheme is proposed so that disturbance rejection-based control is realized for a class of non-minimum phase systems. Numerical simulations are carried out to verify the correctness of the conclusions and the effectiveness of the proposed controller.

Sliding Mode Control of Grid-Connected Neutral-Point-Clamped Converters Via High-Gain Observer

In this article, a nonlinear high-gain observer (NHGO)-based second-order sliding mode (SOSM) control strategy is proposed for the three-phase three-level neutral-point-clamped (NPC) converter. This controller applies the advanced SOSM algorithm both in the voltage regulation loop and in the power tracking loop, which provides a fast dynamic for the dc-link voltage, and also assures a good steady-state behavior for the NPC converter. Additionally, an NHGO technique is implemented in the voltage regulator combining with the SOSM algorithm. The conventional observer-based controllers suffer from the destructive effects of measurement noise, and it can only be addressed by diminishing the observer gain, which sacrifices the observer property. The NHGO technique adopts a time varying gain, that is, high gain in transient while low gain in steady state, which minimizes the adverse influence of measurement noise. The tuning method of the proposed NHGO-based SOSM controller is given to simplify the implementation process. Finally, the simulation and experimental results of the proposed control scheme for the NPC converter are given and compared with the conventional PI controller as well as the well-known linear extended state observer-based control method, which validates the feasibility and superiority of the proposed controller.

Extended state observer-based control with an adjustable parameter for a large ground-based telescope

The high-precision requirements will always be constrained due to the complicated operating conditions of the ground-based telescope. Owing to various internal and external disturbances, it is necessary to study a control method, which should have a good ability on disturbance rejection and a good adaptability on system parameter variation. The traditional proportional-integral (PI) controller has the advantage of simple and easy adjustment, but it cannot deal with the disturbances well in different situations. This paper proposes a simplified active disturbance rejection control law, whose debugging is as simple as the PI controller, and with better disturbance rejection ability and parameter adaptability. It adopts a simplified second-order extended state observer (ESO) with an adjustable parameter to accommodate the significant variation of the inertia during the different design stages of the telescope. The gain parameter of the ESO can be adjusted online with a recursive least square estimating method once the system parameter has changed significantly. Thus, the ESO can estimate the total disturbances timely and the controller will compensate them accordingly. With the adjustable parameter of the ESO, the controller can always achieve better performance in different applications of the telescope. The simulation and experimental verification of the control law was conducted on a 1.2-meter ground based telescope. The results verify the necessity of adjusting the parameter of the ESO, and demonstrate better disturbance rejection ability in a large range of speed variations during the design stages of the telescope.

Extended state observer-based control of heartbeat described by heterogeneous coupled oscillator model

In this paper, a novel framework to investigate the effect of external electrical signals on cardiac rhythm dynamics using the extended state observer-based control (ESOBC) is proposed. Heterogeneous coupled oscillator model (HCOM) is adopted for the generation of P, Ta, QRS, and T waves, and the realistic synthetic electrocardiogram (ECG) due to its capacity for simulating cardiac muscles response. Sinoatrial (SA) and atrioventricular (AV) nodes and His–Purkinje system are described by modified Van der Pol-type (MVDP) equations connected with time-delay velocity coupling. The electrical responses resulted from depolarization (De) and repolarization (Re) of cardiac muscles are separately presented by modified FitzHugh–Nagumo (MFHN) model. The SA and HP pacemakers are coupled with atrial (AT) and ventricles (VT) muscles, respectively, through the stimulation currents. To satisfy the integral chain form of ESO, and deal with the complex structure of the model, including the large number of parameters, and the coupling between the oscillators and interdependent states, three steps are considered. Firstly, a coordinate transformation is proposed for AT and VT responses described by MFHN model to handle mismatched condition. Following this, the nonlinearity of MFHN and the coupling between cardiac muscles and pacemakers are considered as lumped disturbances. Lastly, an extended state observer is designed to compensate the nonlinearity and estimate the unmeasured system states and handle the lumped disturbances. The stability of the closed-loop system is proved, and the effectiveness of the proposed framework for suppressing well-known rhythm disorder, i.e., sinus tachycardia is demonstrated. The framework presented in this work can be easily extended for a wide range of arrhythmia, and serve as an approach to investigate the effect of external stimulation to the heart muscles.

An extended state observer-based control design for electro-hydraulic position servomechanism

The electro-hydraulic servomechanism is widely used in marine vehicles due to its higher power density. However, the servomechanisms suffer from serious throttling loss which leads to its low efficiency, and the parameter uncertainty and disturbances from the changing marine environment damage its control performance. In order to enhance the efficiency of the electro-hydraulic servo system, a robust position control scheme combined with extended state observer (ESO) and finite-time backstepping filtered control (FTBF) technology is developed to compensate for the aggravating performance, while the method of reducing the throttling loss by lower the pressure is adopted. Firstly, with the advantages of the ESO, the robust control without velocity and pressure measurement is realized, and the estimate of the uncertain nonlinear term is obtained. Then, the finite-time design method is introduced to realize the convergence of tracking error in finite time, which possesses a fast error convergence speed and small tracking error. Additionally, the design of a dynamic surface and the adaptive error compensation signals can effectively solve the problem of differential explosion in backstepping design. Finally, the comparative experiment is performed to verify the effectiveness of the controller.

Extended State Observer-Based Control of DC–DC Converters for Fuel Cell Application

Due to the nonlinear volt–ampere characteristic of fuel cell (FC) stack, a dc–dc power converter is essential to be interfaced, to regulate a stiff dc bus to properly power the load. In this article, a robust controller based on extended state observer (ESO) is proposed for a dc–dc interleaved boost converter for FC application. The proportional-integral (PI) control is also designed for comparison. By rewriting the PI control law as the unified form of disturbance observer-based control, it is revealed that the PI control in fact uses the integral action as the disturbance estimation. Then, a theoretical study is conducted to fairly evaluate and compare the performance of these two controllers. The results show that the proposed controller has superior performance to the PI controller, without the need of extra sensors. Simulation and experiment results demonstrate the effectiveness of the proposed controller.

Hybrid extended state observer based control for systems with matched and mismatched disturbances

The conventional Extended State Observer-Based Control (ESOBC) technique is mostly applicable to a class of Integral Chain Form (ICF) structure with the matched kind of single-channel lumped disturbances. However, the systems having the non-ICF structure with the multi-channel matched and mismatched lumped disturbances are widely prevailing in the control applications, where the conventional ESOBC scheme may no longer applicable. To this end, it is recommended to upgrade the conventional ESOBC scheme for enhancing the feasibility and the applicability. This research work addresses the above-discussed recommendations using hybridizing the ESOBC with the Generalized ESOBC (GESOBC) which termed as Hybrid Extended State Observer Based Control (HyESOBC) in this paper. The proposed scheme is capable of estimating and controlling the multi-channel lumped disturbances (i.e., matched and mismatched) for a wide range of practical applications including the systems with the non-ICF structure. Simulation results and comparative analysis of numerical and practical application examples with the dual-channel lumped disturbances are presented to confirm the feasibility and the applicability of the proposed scheme.

Extended state observer-based control for systems with locally Lipschitz uncertainties: LMI-based stability conditions

This paper deals with the closed-loop stability of an extended state observer-based control for systems with locally Lipschitz uncertainties. Novel stability conditions are developed, in terms of Linear Matrix Inequalities (LMI), in order to prove its local/global input-to-state or exponential stability, respectively. The stability conditions of this paper do not require neither the uncertainty to satisfy the so-called matched condition, nor the system to be expressed in the canonical integral chain form. LMI-based optimization methodologies are also developed in order to optimize the presented results.

Linear extended state observer-based control of active lubrication for active hydrostatic journal bearing by monitoring bearing clearance

PurposeThis paper’s aim is modeling and simulation of an advanced controller design for a novel mechatronics system that consists of a hydrostatic journal bearing with servo control. The proposed mechatronic system has more worth in tribology applications as compared to the traditional hydrostatic bearing which has limited efficiency and poor performance because of lower stiffness and load-carrying capacity. The proposed mechatronic system takes advantage of active lubrication to improve stiffness, rotor’s stability and load-carrying capacity.Design/methodology/approachThe current work proposes extended state observer-based controller to control the active lubrication for hydrostatic journal bearing. The advantage of using observer is to estimate unknown state variables and lumped effects because of unmodeled dynamics, model uncertainties, and unknown external disturbances. The effectiveness of the proposed mechatronic system is checked against the traditional hydrostatic bearing.FindingsProposed mechatronics active hydrostatic journal bearing system is checked against traditional hydrostatic journal bearing. It is found that novel active hydrostatic journal bearing with servo control has good tribology performance factors such as stiffness, less rotor vibration, no wear and friction under starting conditions and high load-carrying capacity under different conditions of spindle speed, temperature, initial oil pressure and external disturbance. The result shows that proposed mechatronics system has more worth in rotary tribology applications.Originality/valueThe current manuscript designs a novel active hydrostatic journal bearing system with servo control. The mathematical model has advantages in term of estimating unknown state variables and lumped effects because of unmodeled dynamics, model uncertainties and unknown external disturbances. The result shows improvement in dynamic characteristics of a hydrostatic journal bearing under different dynamic conditions.

Tracking control of uncertain time delay systems: An ADRC approach

This article deals with the control of a class of robotic systems with constant input time delay through the Active Disturbance Rejection paradigm, by means of Generalized Proportional Integral observers. The system is represented as a linear perturbed system, whose lumped disturbance input is estimated and then compensated by an Extended State Observer-Based Control, which is implemented on a predictor scheme for the time delay compensation. A complete Lyapunov Krasovskii functional was used to perform the stability analysis, leading to an ultimate bound trajectory tracking error. The proposal is tested and validated on a two degrees of freedom robotic manipulator.

Enhanced extended state observer-based control for systems with mismatched uncertainties and disturbances

This paper presents an enhanced Extended State Observer (ESO)-based control strategy to deal with the disturbance attenuation problem for a class of non integral-chain systems subject to non-linear mismatched uncertainties and external disturbances. The proposed control strategy does not assume the integral-chain form and it is formed by a state-feedback plus a dynamic disturbance compensation term, which is designed to reject the disturbance effect in the system output. From a theoretical point of view, the proposed strategy is reduced to the conventional ESO when the integral chain form and the matched condition hold. In this sense, this paper is presented as an extension of the ESO principles to cover a wider class of systems. The theoretical results show that the internal zero-dynamics plays an important role in ESO-based control design. Also, the closed-loop stability is analyzed and some numerical simulations show the effectiveness of the proposal in comparison with previous ESO-based techniques.

Feedback Linearization and Extended State Observer-Based Control for Rotor-AMBs System With Mismatched Uncertainties

To effectively reject the influence of moving gimbal effect and parameter variation on the control performance of the rotor-active magnetic bearings (AMBs) system in a double gimbal magnetically suspended control moment gyro (MSCMG), this paper proposes a feedback linearization and extended state observer (ESO) based control (FLESOBC) strategy, which can attenuate the matched and mismatched system uncertainties simultaneously. First, considering the voltage-type power amplifier used in the MSCMG for space applications, the rotor dynamics is modeled completely and then rearranged into translation and tilt motion subsystems according to modal separation control, where the lumped system uncertainties are adopted to represent the external disturbances and the parameter variations. Then, feedback linearization based on differential geometry theory is performed to transform the original system into the integral chain pseudo-linear system, making the mismatched uncertainties in the same channel as the new virtual input. Afterwards, the ESO is designed to estimate the lumped uncertainties. To combine the merits of compensation control and robust control, a PIDD controller (PID with second order differential) is designed to guarantee the closed loop stability and avoid the power amplifier saturation. Finally, simulations and experiments are carried out to demonstrate the effectiveness of the proposed method.

Generalized Extended State Observer Based Control for Systems With Mismatched Uncertainties

The standard extended state observer based control (ESOBC) method is only applicable for a class of single-input-single-output essential-integral-chain systems with matched uncertainties. It is noticed that systems with nonintegral-chain form and mismatched uncertainties are more general and widely exist in practical engineering systems, where the standard ESOBC method is no longer available. To this end, it is imperative to explore new ESOBC approach for these systems to extend its applicability. By appropriately choosing a disturbance compensation gain, a generalized ESOBC (GESOBC) method is proposed for nonintegral-chain systems subject to mismatched uncertainties without any coordinate transformations. The proposed method is able to extend to multi-input-multi-output systems with almost no modification. Both numerical and application design examples demonstrate the feasibility and efficacy of the proposed method.