Fuzzy Disturbance Observer Research Articles

Hopf bifurcation and synchronization of a five-dimensional self-exciting homopolar disc dynamo using a new fuzzy disturbance-observer-based terminal sliding mode control

Having found hidden hyperchaos in a 5D self-exciting homopolar disc dynamo, we study the existence of a Hopf bifurcation, which leads to unstable limit cycles bifurcating from a stable equilibrium. Hidden chaos with only stable equilibria can be observed from the Hopf bifurcation: a typical way to enable hidden attractors to be located. We then provide a new fuzzy controller, and a fast fuzzy disturbance observer, based on terminal sliding mode control for synchronization of the hyperchaotic system. Fuzzy inference is considered to weaken the chattering phenomena. Using Lyapunov stability theory, the stability of the closed-loop system is proved. Finally, simulations of synchronization are illustrated to show the efficient performance of the designed control method via external disturbances and dynamic uncertainties.

Event-triggered interval Type-2 T-S fuzzy control for nonlinear networked systems

In this paper, an event-triggered disturbance attenuation and rejection scheme is proposed for nonlinear networked systems with limited bandwidth and multiple disturbances based on the interval type-2 Takagi-Sugeno fuzzy model. A fuzzy disturbance observer is constructed to estimate the disturbance generated by the exogenous system, and then such kind of disturbance can be rejected. Sufficient conditions are presented such that a fuzzy H∞ controller can be designed to guarantee the stability of the resulting closed-loop system with a prescribed performance index, regardless of disturbances. An event-triggered control scheme is designed to reduce the frequency of the controller updating and thus save the network resources. A numerical example is given to demonstrate the validity of the new design methods presented.

Designing an interval type-2 fuzzy disturbance observer for a class of nonlinear systems based on modified particle swarm optimization

This paper presents a new interval type-2 fuzzy disturbance observer design for a class of nonlinear systems using modified particle swarm optimization. The design procedure has two main parts, including the selection of the initial structure of the type-2 fuzzy disturbance observer, and the optimization of the observer parameters using a modified particle swarm optimization algorithm. The modified particle swarm optimization algorithm has a better performance in terms of the accuracy and convergence rate compared with the standard particle swarm optimization and many other evolutionary algorithms. In this algorithm, the upper and lower bounds of the search space are defined for the parameters of each particle based on their values, and weaker particles are substituted with new particles. To accentuate the outstanding performance of the modified particle swarm optimization for the considered task, its performance is compared with five famous meta-heuristic optimization algorithms. In addition, utilizing interval type-2 fuzzy systems in the proposed observer provides more robustness compared with type-1 fuzzy systems. The effectiveness of the proposed fuzzy disturbance observer is shown through computer simulation and experimental results for the ball and beam system, while the system is subjected to sinusoid and square disturbances, and a comparison is drawn to indicate the superiority of the proposed fuzzy disturbance observer over the other observers.

Synchronization of fractional time-delayed financial system using a novel type-2 fuzzy active control method

In the present article, as a new approach, a fuzzy disturbance observer is combined with an active controller for the synchronization of fractional-order time-delayed systems. Since the type-2 fuzzy logic system shows better performances than the type-1 fuzzy logic system on handling the uncertainties and disturbances, the type-2 fuzzy disturbance observer is utilized in this study. The stability of the proposed method is performed using the Lyapunov stability theorem and active control concept. Then, a fractional-order time-delayed financial system has been investigated, and some features of this chaotic system have been studied. Finally, by applying the proposed control scheme, synchronization results of the fractional-order time-delayed financial system when there exist time-varying disturbances are presented. Numerical simulations demonstrate the robustness and effectiveness of the proposed control technique.

Dissipativity-Based Disturbance Attenuation Control for T-S Fuzzy Markov Jumping Systems With Nonlinear Multisource Uncertainties and Partly Unknown Transition Probabilities.

This article is concerned with the dissipativity-based disturbance attenuation control for a class of Takagi-Sugeno (T-S) fuzzy Markov jump systems (FMJSs) suffering from nonlinear multisource disturbances. The considered system possesses nonlinear and stochastic jumping disturbances generated by multiple sources, constituting the main challenge to control design and dissipativity analysis. By proposing an adaptive fuzzy disturbance observer and a hybrid feedback controller, a novel fuzzy disturbance attenuation control structure has been constructed. In terms of strict linear matrix inequalities (LMIs), a new sufficient condition is established to guarantee the (Z, Y, X)-ε- dissipative and stochastic exponentially stability of the closed-loop FMJSs. Furthermore, for the concerned FMJSs with partly unknown transition probabilities, the sufficient conditions are also derived and the gains of controller or observer can be computed immediately. Finally, a numerical example is provided to verify the effectiveness of the proposed theory.

Adaptive fault tolerant attitude control of flexible satellites based on Takagi-Sugeno fuzzy disturbance modeling

This paper investigates the fault tolerance problem of flexible satellites subject to multiple disturbances and actuator faults. An adaptive fault tolerant control (FTC) approach based on disturbance observer is presented for attitude control system (ACS) with actuator faults, elastic modal, modeling error and environmental disturbance torque in this paper. Different from some existing disturbance observer-based control (DOBC) approaches, Takagi-Sugeno (T-S) fuzzy modeling technology is applied to describe the elastic modal. A fuzzy disturbance observer and a fault diagnosis observer are constructed to estimate the elastic modal and actuator fault, respectively. Then, based on fault accommodation and DOBC, a new adaptive FTC strategy is designed to achieve the anti-disturbance performance and improve the system reliability. Finally, the efficiency of the proposed FTC scheme is verified by simulation results.

Fuzzy Model Predictive Control With Enhanced Robustness for Nonlinear System via a Discrete Disturbance Observer

This paper addresses the tracking accuracy and robustness enhancement problems of fuzzy model based predictive control (MPC) for a class of nonlinear systems subjecting to lumped disturbances composed of bounded unknown disturbances and a model-plant mismatch. Main features of the proposed method are: 1) A fuzzy disturbance observer and an auxiliary controller are jointly developed to meet a certain control objective that minimizes the peak bound of the errors caused by the lumped disturbances, which eventually leads to desired offset-free tracking performance. 2) A pre-computed robust positively invariant set whose central is the nominal state is derived with the premise of input-to-state stability. 3) Tightened constraints for the guarantee of recursive feasibility of MPC is computed off-line and the quasi-min-max fuzzy MPC is elaborately designed according to a piecewise Lyapunov function. Furthermore, characteristics of robustness enhancement and low on-line computational burden are obtained as compared with the existing offset-free MPCs, and further the impacts of estimation error arising from sampling time and admissible target set on the system performance are also discussed. Two simulation examples verify the effectiveness of the proposed approach ensuring the satisfaction of constraints.

Adaptive Fuzzy Dynamic Surface Control for Multi-Machine Power System Based on Composite Learning Method and Disturbance Observer

A composite learning dynamic surface control is proposed for a class of multi-machine power systems with uncertainties and external disturbances by using fuzzy logic systems (FLSs) and disturbance observer (DOB). The main characteristics of the proposed strategy are as follows: (1) The approximation ability of FLSs for nonlinear model of multi-machine power systems is enhanced considerably by using the composite learning method and providing additional correction information for the FLSs. These findings differ considerably from previous designs that focus directly on the system's tracking performance. (2) The filtering errors caused by the utilizations of the first-order low-pass filters in dynamic surface control (DSC) are compensated effectively by designing the compensating signals in the control law design process. (3) The compound disturbances including the FLSs' approximation error and external disturbances are estimated and mitigated by constructing DOB. Finally, the proposed control algorithm is verified on the StarSim Hardware-in-loop experimental platform, and the experimental results validate the effectiveness of the proposed control strategy in suppressing disturbances and enhancing the robustness of the controller.

A fuzzy disturbance observer based control approach for a novel 1-DOF micropositioning mechanism

This paper presents the design, analysis, and control of a novel compact, large range 1-DOF micro manipulation mechanism. Leaf flexures were incorporated into a modular multilayer design configuration to achieve large range motion with a high natural frequency. The modular design of the proposed mechanism makes it usable as a building block to construct higher DOF-mechanisms. Computational analysis was conducted to verify the static and dynamic responses of the proposed mechanism and to ensure low flexures stress, high natural frequency, and large workspace. The mathematical model was developed to establish the derivation of a robust observer-based Sliding Mode (SM) controller. To improve the precision of tracking performance, the SM controller was augmented with adaptive Fuzzy Disturbance Observer (SM-FDO). Another robust control technique (H∞) was implemented in this work to characterize and compare the performance of SM-FDO. The mechanism was fabricated using 3D printing technology and a Voice Coil Motor (VCM) was used to deliver the actuation for its capability to provide large displacements. Experiments were performed to verify the computational modeling of the proposed mechanism and to evaluate the performance of the developed controllers. Several experimental results showed that the adaptive nature of SM-FDO allowed this controller to have superior robustness and tracking performance over the other implemented robust controller.

Fuzzy Disturbance Observer-Based Adaptive Sliding Mode Control for Reusable Launch Vehicles With Aeroservoelastic Characteristic

This paper investigates the problem of attitude tracking control for reusable launch vehicles (RLVs) with aeroservoelastic characteristic and disturbances in reentry phase. An aeroservoelastic model for reentry RLV is first established, where the synthetic disturbances are considered as well. Then a novel disturbance observer combined with fuzzy logic system is constructed by using both fuzzy approximation error and observation error to provide the disturbance estimation. The fuzzy disturbance observer (FDO) can be employed to the control scheme to counteract the perturbations and guarantee the estimation errors for converging to a small neighborhood around origin. Incorporated with the designed FDOs, the adaptive sliding mode technique is proposed for developing attitude angle and angular rate subsystem controllers, respectively, to ensure the reentry attitude tracking performance. Rigorous proof shows that the uniform stability of the closed-loop system under the proposed control law can be guaranteed by using Lyapunov technique. Finally, numerical simulations are conducted in this paper to illustrate the effectiveness of the developed technique for the RLV.

Disturbance observer‐based integral fuzzy sliding‐mode control and its application to wind turbine system

In this study, a disturbance observer-based integral fuzzy sliding-mode control methodology for a wind turbine system with a non-linear permanent magnet synchronous generator (PMSG) is proposed using the Takagi–Sugeno fuzzy model. To reduce the hardware cost of the fuzzy controller membership function, an imperfect premise matching condition is considered. Considering the matched disturbance, and an external disturbance acting on the system, a novel integral fuzzy sliding surface is proposed based on a fuzzy disturbance observer (FDOB). Therefore, various forms of external disturbances can be estimated using the FDOB. In addition, a sufficient condition for guaranteeing the asymptotic stability of the sliding motion with performance is proposed using a Lyapunov function and derived using a linear matrix inequality format. Furthermore, a reachability problem of the system states over the proposed sliding surface is derived through an appropriate Lyapunov function. Finally, the simulations for a wind turbine system using a PMSG are implemented to verify the effectiveness of the proposed method as compared with previous studies.

Adaptive dynamic surface control using disturbance observer for nonlinear systems with input saturation and output constraints

ABSTRACTAn adaptive dynamic surface control (DSC) approach using fuzzy approximation and nonlinear disturbance observer (NDO) for uncertain nonlinear systems in the presence of input saturation, output constraint and unknown external disturbances is proposed in this paper. The issue of input saturation is addressed by introducing a lower bound assumption on the approximation function of saturation. The output constraint is handled by introducing an appropriate barried Lyapunov function. The nonlinear disturbance observer (NDO) is employed to estimate the unknown unmatched disturbances. It is manifested that the ultimately bounded convergence of all the variables in the closed-loop system is guaranteed and the tracking error can be made farely small by tuning the design parameters. Finally, two simulation examples illustrate the effectiveness and feasibility of the proposed approach.

Fuzzy Disturbance Observer-Based Sliding Mode Control for Liquid-Filled Spacecraft With Flexible Structure Under Control Saturation

This paper investigates a fuzzy disturbance observer (FDO)-based terminal sliding mode control (TSMC) strategy for the liquid-filled spacecraft with flexible structure(LFS-FS) under control saturation. Firstly, a novel FDO is designed to estimate the lumped uncertainty, including the inertia uncertainty, external disturbance, the coupling of liquid slosh and flexible structure(LF), as well as the parts that exceed control saturation. The merits of the FDO lie in that estimation error can be arbitrarily small by adjusting the designed parameters and the prior information is not required. Then, based on the estimation of FDO, a finite-time TSMC is designed, which has more satisfactory control performance, such as chattering reduction and fast convergence speed. The stability of the closed-loop system is proved strictly by Lyapunov theory. Finally, numerical simulations are presented to demonstrate the effectiveness of the proposed method.

Fuzzy disturbance observer‐based dynamic surface control for air‐breathing hypersonic vehicle with variable geometry inlets

For an air-breathing hypersonic vehicle with a variable geometry inlet (AHV-VGI), a movable translating cowl is used to track the shock on lip conditions to capture enough air mass flow, which can extend the velocity range and be favourable to the acceleration and manoeuvring flight. The authors firstly establish longitudinal dynamics for AHV-VGI, and consider the lumped disturbances which include the unknown external disturbance, the parameter uncertainties and the uncertainty parts introduced by translating cowl. Then, the dynamic surface control strategy based on a fuzzy disturbance observer (FDO) is proposed for AHV-VGI control. The control process for AHV-VGI is divided into two subsystems. For each subsystem, a sliding mode controller is designed, and FDOs are adopted to compensate the lumped disturbances, which can render the disturbance estimate errors convergent. Numerical simulations are presented to illustrate the effectiveness of the proposed method and the advantages of translating cowl.

A new fuzzy-disturbance observer-enhanced sliding controller for vibration control of a train-car suspension with magneto-rheological dampers

Abstract Semi-active train-car suspensions are always impacted negatively by uncertainty and disturbance (UAD). In order to deal with this, we propose a novel optimal fuzzy disturbance observer-enhanced sliding mode controller (FDO-SMC) for magneto-rheological damper (MRD)-based semi-active train-car suspensions subjected to UAD whose variability rate may be high but bounded. The two main parts of the FDO-SMC are an adaptive sliding mode controller (ad-SMC) and an optimal fuzzy disturbance observer (op-FDO). As the first step, the initial structures of the sliding mode controller (SMC) and disturbance observer (DO) are built. Adaptive update laws for the SMC and DO are then set up synchronously via Lyapunov stability analysis. Subsequently, an optimal fuzzy system (op-FS) is designed to fully implement a parameter constraint mechanism so as to guarantee the system stability converging to the desired state even if the UAD variability rate increases in a given range. As a result, both the ad-SMC and op-FDO are formulated. It is shown from the comparative work with existing controllers that the proposed method provides the best vibration control capability with relatively low consumed power.

하중 적분 PDC와 T-S 퍼지 외란 관측기를 이용한 이동 로봇의 강인 궤도 추적 제어

하중 적분 PDC와 T-S 퍼지 외란 관측기를 이용한 이동 로봇의 강인 궤도 추적 제어

Reliable control for bilateral teleoperation systems with actuator faults using fuzzy disturbance observer

In this study, the synchronisation problem of bilateral teleoperation systems with time-delay and actuator faults is considered. First, the error dynamic system with actuator faults is modelled as a time-delay system with disturbance, and a fuzzy disturbance observer (FDO) is designed to estimate the unknown non-linear disturbance. Moreover, an FDO-based robust controller is provided for the master robot and a reliable controller is designed for the slave robot, respectively. Next, a sufficient condition is given to ensure the tracking error; the disturbance observation error and the parameter error are uniformly ultimate bounded. Finally, a numerical example is shown to illustrate the effectiveness of the proposed method.

Disturbance Rejection Fuzzy Control for Nonlinear Parabolic PDE Systems via Multiple Observers

A design method of low-dimensional disturbance rejection fuzzy control (DRFC) via multiple observers is proposed for a class of nonlinear parabolic partial differential equation (PDE) systems, where the disturbance is modeled by an exosystem of ordinary differential equations (ODEs) and enters into the PDE system through the control channel. In the proposed scheme, the modal decomposition technique is initially applied to the PDE system to derive a slow subsystem of low-dimensional nonlinear ODEs, which accurately captures the dominant dynamics of the PDE system. The resulting nonlinear slow subsystem is subsequently represented by a Takagi–Sugeno (T–S) fuzzy model. From the T–S fuzzy model and the exosystem, a fuzzy slow mode observer and a fuzzy disturbance observer are constructed to estimate the slow mode and the disturbance, respectively. Furthermore, a nonlinear observation spillover observer is proposed to compensate the effect of observation spillover. Then, based on these observers, a low-dimensional DRFC design is developed in terms of linear matrix inequalities to guarantee the exponential stability of the closed-loop PDE system in the presence of the disturbance. Finally, the effectiveness of the proposed design method is demonstrated on the control of one-dimensional Burgers–KPP–Fisher diffusion–reaction system and the temperature profile of a catalytic rod.

High-performance motion control of the hydraulic press based on an extended fuzzy disturbance observer

This article focuses on the high-performance motion control problem of the hydraulic press. Smooth and precise motion control of the hydraulic press is hardly achieved due to the complex external disturbances which typically consist of the deformation force and friction force. An extended fuzzy disturbance observer is first constructed to estimate and compensate the hardly modeled deformation force. The proposed extended fuzzy disturbance observer differs with the fuzzy disturbance observer on parameter adaptation; the fuzzy disturbance observer is commonly driven by the disturbance observer error, while the designed extended fuzzy disturbance observer is driven by the disturbance observer error and the motion tracking error together. The nonlinear cascade controller is further applied to synthesize the motion controller considering the particular work principle of the separate meter-in separate meter-out drive system adopted in the hydraulic press. The outer motion tracking loop of the nonlinear cascade controller is designed based on the sliding mode control with the desired driving force as control output, and the inner pressure control loop of the nonlinear cascade controller uses the backstepping technique to make the separate meter-in separate meter-out drive system track the desired driving force precisely. The minimum equivalent load criterion is proposed to act as the bridge linking the outer and inner loop. The stability of the overall closed-loop system is proved based on the Lyapunov theory. The performance of the proposed scheme is verified through the simulations and experiments. The results demonstrate that the nonlinear cascade controller together with the extended fuzzy disturbance observer provides an excellent motion tracking performance in the presence of complex external disturbances.

Adaptive dynamic surface control based on fuzzy disturbance observer for drive system with elastic coupling

This paper proposes an adaptive control strategy by employing dynamic surface control (DSC) technique and fuzzy disturbance observer (FDO) for the two-inertia system with uncertainties and external disturbance. Firstly, the unknown elements including uncertainties and external disturbance are estimated by using a fuzzy disturbance observer which does not need a priori information of these unknown dynamics. Next, the estimations of unknown disturbance are integrated into DSC design by using recursive feedbacks to damp torsional vibration. The ‘explosion of complexity’ in conventional backstepping technique is avoided by introducing first-order filters. The stability analysis of the design scheme is verified based on the Lyapunov stability theory. All the signals in the closed-loop system are guaranteed to be uniformly ultimately bounded and the tracking error can be made arbitrarily small by adjusting the design parameters. Comparative simulations and experiments demonstrate the effectiveness and applicability of the proposed method.