Fuzzy Disturbance Observer Research Articles

Fuzzy disturbance observer-based fuzzy swing suppression control of a ‘mooring-heavy lift crane-cargo’ coupled system

In this paper, an adaptive fuzzy disturbance observer (FDO)-based control is proposed for the swing suppression of the mooring-heavy lift crane (HLC)-cargo system in the presence of a wave disturbance. First, the dynamic model of the HLC system is determined by employing the Lagrangian method, and the wave force is modeled as an exosystem with unknown terms based on the Jonswap spectrum. Then, based on the HLC model and the wave force exosystem, an FDO is established to determine the wave disturbances, and a fuzzy approximator is developed to estimate the unknown terms. A novel disturbance estimation error observer is first developed to facilitate the parameter adaptive updating law. Subsequently, by augmenting the HLC system and disturbance estimation error system, an FDO-based fuzzy antiswing control method is proposed in terms of the linear matrix inequality technique to suppress the swing. The closed-loop system stability is examined by using the Lyapunov method. Finally, the effectiveness of the proposed method is validated by numerical simulation.

Fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode spacecraft attitude control under time-varying output constraints

This article proposes a fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode spacecraft control scheme with consideration of input uncertainties and unknown nonlinearities. First, for the purpose of satisfying the time-varying output constraints and simplifying the computational process, an error transformation function is employed to convert the constrained spacecraft system into an unconstrained one. Second, to ensure superior transient-state performance, an improved sliding manifold integrated with a nonlinear function is designed. Then, for accurately estimating the external disturbances, a fixed-time fuzzy disturbance observer is proposed. Furthermore, the unknown nonlinearities and the input uncertainties are handled by several adaptive laws. The simulation results are presented to verify the superiority and effectiveness of the proposed fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode control scheme.

Virtual Reference-Based Fuzzy Noncascade Speed Control for PMSM Systems With Unmatched Disturbances and Current Constraints

This paper aims to develop a non-cascade speed control approach for permanent magnet synchronous motor (PMSM) systems based on the Takagi–Sugeno (T–S) fuzzy model. In non-cascade control structures, the lack of firsthand current references imposes a tricky challenge in dealing with current constraints from the circuit and unmatched disturbances caused by load torques. To this end, a virtual reference-based fuzzy non-cascade speed control scheme is proposed for PMSM systems. First, unmatched load torques are estimated by a fuzzy disturbance observer. And then, a novel virtual reference planner is constructed to inject the estimated unmatched disturbance into the control channel as feedback compensation. This improves anti-disturbance performance, while keeping the current re-sponse within the feasible domain and reducing speed overshoot. Furthermore, the non-cascade speed regulation problem is con-verted into a system stabilization problem and addressed by the composite control strategy based on the non-parallel distributed compensation. Finally, closed-loop stability with reduced con-servatism is ensured through the fuzzy Lyapunov functions and improved slack variables. Simulations and experiments show that the proposed scheme achieves excellent speed response without overcurrent even under mismatched load torque variations.

Data-Driven Based Model-Free Adaptive Optimal Control Method for Hypersonic Morphing Vehicle

Aiming at the attitude control of a class of hypersonic morphing vehicles (HMVs) with variable sweep wings, a model-free adaptive dynamic planning (MFADP) optimal control method based on data-driven and finite-time fuzzy disturbance observer is proposed in this paper. An integrated oriented-control attitude-morphing model is established, and morphing is considered as the state to carry out the integrated coupling attitude control. The control scheme is organized by a steady-feedback-compensation framework. To overcome the dependence on the unknown dynamic knowledge of HMVs, the dynamic model is reconstructed using neural networks for steady-state control. Subsequently, based on the MFADP algorithm, an Off-On serial policy learning strategy is designed for the error model to obtain a real-time approximate optimal feedback control. Additionally, a fuzzy disturbance observer with finite-time convergence ability is proposed to estimate and compensate the multiple uncertainties. Finally, the stability of the closed-loop system is proved theoretically and the simulation results demonstrate the improved performance of the proposed method.

Fuzzy-aided finite-time frequency controller of renewable-integrated power systems with hydrogen energy storage

Reliable frequency regulation of power systems integrated with low-inertia variable renewable energy generations (REGs) is crucial in islanded mode operation. It demands a resilient control framework to uphold grid stability/security against undeniable physical disturbances/cyber-attacks. This work maidenly develops and applies a fuzzy disturbance observer (FDO)-based resilient frequency controller to advance the dynamic stability of REGs-integrated large-scale power plants. Further, to enhance the damping of frequency/power oscillations, hydrogen energy storage (HES) has been incorporated, and its effectiveness is analyzed. The estimated disturbance using FDO is augmented into secondary control law derived from a non-singular terminal sliding mode strategy to increase active disturbance rejection proficiency of the overall closed-loop system. The global exponential finite-time stability of the testbed under the developed control framework has been rigorously reviewed using the Lyapunov theory. The qualitative assessment of simulation outcomes has confirmed the proficiency and resiliency of the developed control framework regarding superior frequency regulation against unknown disturbance inputs. The practicability of the developed control framework has been further quantified on IEEE 68-bus large-scale testbed, and a comparative study is presented following unknown/uncertain disturbances. Lastly, the cyber-tolerance of the applied resilient controller has been established against detectable DoS cyber-attack.

Dynamic Event-Triggered Adaptive Tracking Control for Multiagent Systems with Power Exponential Function Using Fuzzy Disturbance Observer

Dynamic Event-Triggered Adaptive Tracking Control for Multiagent Systems with Power Exponential Function Using Fuzzy Disturbance Observer

Antidisturbance Control Design for Interval Type-2 Fuzzy Stochastic Systems With Input Quantization

Quantized anti-disturbance control design problem is presented for a class of interval type-2 (IT2) fuzzy stochastic systems subject to time delays and multiple disturbances. The inherent uncertain nonlinear and hybrid characteristics of the concerned system make it difficult to design a stable anti-disturbance controller. In order to properly reflect the characteristics of IT2 fuzzy stochastic models with multiple disturbances, a new fuzzy disturbance observer is proposed to estimate the disturbances generated by a fuzzy exogenous system. Furthermore, a quantized fuzzy anti-disturbance control scheme is synthesized by fusing the estimation of the multiple disturbances. With the support of Lyapunov functional method, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$It{\hat{o}}$</tex-math></inline-formula> 's formula and auxiliary function-based integral inequality, the resulting IT2 fuzzy stochastic systems are proved to be robustly stochastically stable with mixed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_\infty$</tex-math></inline-formula> /passivity performance index. The design methods of the fuzzy disturbance observer and quantized anti-disturbance controller are formulated in the form of linear matrix inequalities so that the corresponding gain matrices can be easily obtained. Finally, simulation studies on three examples are provided to justify the efficiency of the designed control strategy.

Text message secure communication based on fractional-order chaotic systems with Takagi–Sugeno fuzzy disturbance observer and sliding mode control

Text message secure communication based on fractional-order chaotic systems with Takagi–Sugeno fuzzy disturbance observer and sliding mode control

Adaptive fuzzy control of underwater vehicle manipulator system with dead-zone band input nonlinearities via fuzzy performance and disturbance observers

In this paper, an adaptive fuzzy control design problem is investigated for an underwater vehicle manipulator system (UVMS) based on a fuzzy performance observer (FPOB) and fuzzy disturbance observer (FDO). The UVMS is considered as a nonlinear system comprising model uncertainties, external disturbances and dead-zone band input nonlinearities. To mitigate the combined effects of the dead-zone and the hysteresis, a novel pre-deadzone compensator is proposed. Then, fuzzy logic systems (FLSs) with online adaptations are utilized to evaluate the unknown components of the inertia matrix, the Coriolis matrix and the damping matrix. In addition, a fuzzy performance observer is constructed whose errors are used to estimate the external disturbances. Further, an H∞ fuzzy control technique is developed to reduce the errors in estimating the external disturbance. Then, the stability and tracking performance of the closed-loop system are analyzed using the Lyapunov stability theory. It is shown that all signals of the closed-loop system are uniformly ultimately bounded. Finally, simulations are performed to demonstrate the effectiveness of the proposed control scheme in addressing the tracking control problem of the UVMS in presence of the dead-zone band and disturbances.

Disturbance observer-based fuzzy event-triggered ISMC design: Tracking performance

This article presents a disturbance observer (DO)-based event-triggered integral sliding mode tracking control (ISMTC) for continuous-time Takagi–Sugeno (T–S) fuzzy model (TSFM) subject to external disturbances. Merging the event-triggered control (ETC) with integral sliding mode control (ISMC) approach is led to reach the better accommodate the features of ISMC. To do this, two forms of fuzzy integral sliding surfaces (FISSs) are proposed. The first is the periodic-time-based FISS that is presented to provide the robustness of the tracking performance from the initial moment. The second is the event-triggered-based FISS which is proposed to obtain the fuzzy event-triggered ISMTC law. To more decrease the chattering effects and compensate the tracking performance against the disturbances, a fuzzy disturbance observer (FDO) is proposed to estimate the mismatched disturbances. Compared with the existing works, a more practical controller is proposed based on the asynchronous premise variables. Utilizing the common quadratic Lyapunov function, appropriate conditions are derived to verify that the tracking error is robust from the initial moment. Furthermore, by adopting a decaying triggering threshold, it is guaranteed that the system is Zeno-free during the process. To verify the effectiveness of the suggested event-triggered ISMTC, a practical system including continuous stirred tank reactor (CSTR) is simulated and the results are compared.

Observer-based optimal control method combination with event-triggered strategy for hypersonic morphing vehicle

A morphing-attitude coupling control method based on event-triggered adaptive dynamic programming (ETADP) and a finite-time fuzzy disturbance observer (FTFDO) is proposed for a class of hypersonic morphing vehicle (HMV). Firstly, an attitude-morphing coupled dynamic model is established, and the morphing variable is treated as the state for integrated control with attitude. The control law is updated by an event-triggered mechanism, which is designed in two parts: feedforward control and feedback control. Based on the proposed FTFDO, the matched and mismatched uncertainties are estimated and compensated in finite time to solve the feedforward control input. Based on an adaptive dynamic programming algorithm, Critic-Actor dual networks are constructed to implement policy iteration for an approximate optimal feedback control policy by offline training with exploration. The Critic-Actor dual networks then adopt the ETADP algorithm to tune the weight of the networks online when triggering criteria for policy improvement are met. Event-triggered conditions are developed such that the feedforward control and feedback control are both updated by aperiodic sampling, reducing the number of controller updates required. Zeno behavior is avoided by determining the minimum sampling interval time. The stability of the closed-loop system is demonstrated theoretically. Simulation results verify the control efficiency and robustness of the proposed method.

Adaptive sliding mode fault-tolerant attitude control for flexible satellites based on T-S fuzzy disturbance modeling.

This paper investigates the fault tolerance problem of flexible satellites subject to actuator faults and multiple disturbances. An adaptive sliding mode fault tolerant control (ASMFTC) approach based on Takagi-Sugeno (T-S) fuzzy disturbance observer (TSFDO) is presented for attitude control system (ACS) under loss of actuator effectiveness, environmental disturbance torque and elastic modal generated by flexible appendages. Compared with the traditional disturbance observer based control (DOBC) methods, the T-S fuzzy technology is applied to estimate the unknown nonlinear elastic modal. Then, the energy bounded disturbance is eliminated by designing an adaptive sliding mode controller. The proposed ASMFTC design can guarantee the sliding surface to approach zero. Finally, the effectiveness of the control method proposed in this paper is further verified by comparative simulation.

Dynamic Event-Triggered Antidisturbance Control for Flexible Spacecraft Systems

This study develops a dynamic event-triggered anti-disturbance (DETAD) controller to solve attitude control problem for flexible spacecraft systems with multiple disturbances. The disturbances involve two aspects: one belongs to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_{2}$</tex-math></inline-formula> space, and the other is described by an exogenous nonlinear system. Two sets of Takagi–Sugeno (T–S) fuzzy models are employed to model the flexible spacecraft systems and an exogenous nonlinear system, respectively. Moreover, a flexible vibration observer (FVO) is introduced to estimate the flexible modes. And a fuzzy disturbance observer (FDO) is designed to estimate the T–S fuzzy modeling disturbance in the case of the unmeasurable premise variables. By utilizing the estimations of two observers, a DETAD controller is constructed, where a dynamic event-triggered mechanism is implemented to reduce communication transmission. Additionally, new sufficient conditions for the closed-loop system to be asymptotically stable with strict dissipative performance are formed using linear matrix inequality techniques. Simulations are also provided to verify the advantages of the proposed scheme for flexible spacecraft systems subject to different types of disturbances.

Disturbance observer-based nonfragile fuzzy tracking control of a spacecraft

This paper deals with the nonfragile fuzzy tracking control technique of a spacecraft subject to external disturbances and control gain uncertainties. First, the Takagi–Sugeno (T–S) fuzzy model of the tracking error dynamics is newly derived. Unlike the existing studies, we assume that the controller output is norm bounded and its gain matrix is perturbed because of the aging of the actuator. Next, a fuzzy disturbance observer (DOB) estimating the external disturbance is constructed to enhance the robustness of the control system. Then, a fuzzy controller feeding back the estimated disturbance is designed to attenuate external disturbances. In addition, we establish the linear matrix inequality (LMI) conditions, by which both the H∞ disturbance attenuating performance and the asymptotic stabilization are guaranteed. From the solution to the LMI conditions, we obtain the controller and DOB gain matrices. Finally, a simulation example validates the disturbance estimation and tracking performance of the proposed method.

Interval Type-2 Fuzzy Disturbance Observer-Based T–S Fuzzy Control for a Pneumatic Flexible Joint

In this article, an interval type-2 fuzzy disturbance observer (IT2FDO) is proposed for the trajectory tracking control of a flexible joint actuated by a pneumatic artificial muscle and a torsion spring. Interval type-2 fuzzy sets are introduced into the fuzzy disturbance observer (FDO) to enhance the fuzzy approximation capability. A novel adaptive law that updates all the parameters of the FDO, including the control representative values, the center vectors, and the width vectors, is developed. A new control strategy incorporating the proposed IT2FDO and Takagi&#x2013;Sugeno (T&#x2013;S) fuzzy model-based control is designed for the trajectory tracking task. With the newly designed adaptive law, the stability of the IT2FDO and that of the closed-loop system are guaranteed. Simulation studies verify the effectiveness of the proposed IT2FDO, and real-world experiments demonstrate the robustness of the proposed control strategy to the external disturbance.

Sliding mode control for IT2 fuzzy semi-Markov systems with faults and disturbances

The composite fault-tolerant control problem for semi-Markov jumping nonlinear systems with time delays, uncertainties faults and multiple disturbances is addressed in this paper. The main intention of this work is to design a sliding mode control (SMC) law via an interval type-2 (IT2) fuzzy approach in such a way that it attenuates and rejects the impacts of uncertainty, nonlinearity, faults and external disturbances. Notably, first, an IT2 fuzzy disturbance observer is formulated to estimate the external disturbances and then an IT2 fuzzy fault diagnosis observer is designed to estimate the faults effectively. Next, a SMC-based fault-tolerant strategy is developed to compensate the diagnosed faults and disturbances satisfactorily. By using the linear matrix inequality and Lyapunov technique, the required stability constraints are developed with prescribed H∞ performance index. The importance and effectiveness of the developed composite fault-tolerant control scheme are finally validated through two numerical examples.

Adaptive Control for Multi-Shaft with Web Materials Linkage Systems

In this paper, a fuzzy disturbance observer and a high-gain disturbance observer based on a variable structure controller are applied to deal with imprecise multi-shaft with web materials linkage systems taking into account the variation of the moment of inertia. Specifically, a high-gain disturbance observer and an adaptive fuzzy algorithm are separately applied to estimate system uncertainties and external disturbances. The high-gain disturbance observer is designed with auxiliary variables to avoid the amplification of the measurement disturbance, and the fuzzy disturbance observer has the advantage that it does not depend on model information. The convergence properties of the tracking error are analytically proven using Lyapunov’s theory. The obtained numerical results demonstrate the validity and the adaptive performance of the proposed control law in case the system is exposed to uncertainties and disturbances. Important remarks on the design process and performance benchmarks of the two observers are also demonstrated.

Fuzzy Disturbance Observer Design for a Class of Nonlinear SISO Systems

Fuzzy Disturbance Observer Design for a Class of Nonlinear SISO Systems

Adaptive fuzzy-based composite anti-disturbance control for a class of switched nonlinear systems with unknown backlash-like hysteresis

For a class of switched nonlinear systems with unmatched external disturbances and unknown backlash-like hysteresis, an adaptive fuzzy-based control strategy is proposed to handle the anti-disturbance issue. The unmatched external disturbances come from a switched exosystem. Our aim is to achieve the output tracking performance and the disturbance attenuation by using the adaptive fuzzy-based composite anti-disturbance control technique. First, based on the fuzzy logics, we design a switching adaptive fuzzy disturbance observer to estimate unmatched external disturbances. Second, a composite switching adaptive anti-disturbance controller is constructed. By means of the backstepping technique, disturbance estimations are added in each virtual control to offset the unmatched disturbances, which results in the different coordinate transformations. At last, the availability of the proposed approach is illustrated by a mass-spring-damper system.

Disturbance observer based adaptive fuzzy sliding mode control: A dynamic sliding surface approach

In this paper, the disturbance observer based adaptive sliding mode control (SMC) approaches are established for Takagi–Sugeno fuzzy systems with unknown external disturbance. In order to counteract the disturbance actively, a novel memory-based fuzzy disturbance observer is proposed to estimate the unknown disturbance. In the absence of upper bound information of the disturbance estimation errors, by designing novel dynamic sliding surfaces and adaptive laws, both the state- and output-based adaptive fuzzy sliding mode controllers are designed without any constraints on input matrices, and the disturbance estimate is incorporated to achieve active disturbance rejection. It can be shown that, with the proposed control approaches, both the sliding variables and the adaptive parameter estimation errors will converge to the bounded region in fixed-time. Finally, numerical examples are presented to show the effectiveness of the proposed control approaches.