Composite Anti-disturbance Control Research Articles

Finite-time boundedness analysis and composite anti-disturbance control for uncertain semi-Markovian jump systems with time delay

Finite-time boundedness analysis and composite anti-disturbance control for uncertain semi-Markovian jump systems with time delay

Composite anti-disturbance dynamic positioning of vessels with modelling uncertainties and disturbances

This paper presents a composite anti-disturbance control scheme for the dynamic positioning (DP) of the surface vessels with modelling uncertainties and ocean environmental disturbances. The composite control design builds on integrating the disturbance observer together with the H∞ optimal control. The composite control structure consists of the inner layer disturbance compensator and the outer layer attenuation controller. The inner layer disturbance compensator rejects slowly varying disturbances due to wave drifts, utilizing estimations from the disturbance observer. The outer layer attenuation controller attenuates norm-bounded disturbances due to residual filtered wave-induced disturbances as well as modelling uncertainties. The composite control scheme provides the computational efficiency. The DP motion closed-loop analysis proves that the composite anti-disturbance control maintains the vessel’s position and heading at the reference points and guarantees the closed-loop control stability. Simulations and comparisons on a supply vessel verify the availability and the superiority.

Composite anti‐disturbance control for semi‐Markovian jump systems with time‐varying delay and generally uncertain transition rates via disturbance observer

The problem of composite anti-disturbance control for semi-Markovian jump systems (S-MJSs) with time-varying delay via disturbance observer is analysed in this study. Unlike the existing methods, generally uncertain transition rates, time-varying delay, multiple disturbances, the H ∞ performance and disturbance-observer-based control (DOBC) are all considered in S-MJSs. The method which combines DOBC and H ∞ control is used to guarantee the system performance level of time-varying delay S-MJSs. Firstly, a sufficient condition of stochastic stability in the H ∞ performance level for the composite control system is given by using piecewise Lyapunov–Krasovskii functional. Secondly, the optimal value of disturbance suppression level for the system is solved by an optimisation algorithm. Thirdly, variation interval of time-delay has been divided into equal small intervals for reducing the conservatism of the method which addresses the mode-dependent time-delay problem. Furthermore, the composite controller and disturbance observer which satisfy the proposed stability condition are designed to address the composite anti-disturbance control problem of the closed-loop system. Finally, two practical systems are provided to testify the accuracy of research methods.

Dissipativity-Based Composite Antidisturbance Control for T–S Fuzzy Switched Stochastic Nonlinear Systems Subjected to Multisource Disturbances

In this article, a dissipativity-based composite antidisturbance control structure is constructed for Takagi–Sugeno (T–S) fuzzy switched stochastic nonlinear systems subjected to multisource disturbances. The inherent uncertain nonlinear and hybrid characteristics of the concerned system make it difficult to design a stable antidisturbance controller. To properly accommodate the characteristics of T–S fuzzy multisource disturbances and system models, a novel fuzzy switched disturbance observer is put forward to estimate the disturbances generated by a switched exogenous system. Then, a fuzzy composite antidisturbance control law is synthesized by fusing the estimation of the multisource disturbances and the state-feedback control scheme. By using the average dwell time technique and piecewise Lyapunov functions, it is proved that the resultant closed-loop system are stochastically stable and strictly $({{\mathscr Z},{\mathscr Y},{\mathscr X}})-\varepsilon -$ dissipative. The sufficient conditions for the existence of the fuzzy switched disturbance observer and state-feedback controller are established in terms of linear matrix inequalities, and the control and observation gains can be solved directly. Finally, a numerical example is presented to illustrate the effectiveness and favor performance of the proposed control algorithm.

Composite anti-disturbance control for stochastic systems with multiple heterogeneous disturbances and input saturation

This paper develop a novel composite anti-disturbance control (CADC) method for a class of stochastic nonlinear systems in which input saturation and multiple heterogeneous disturbances occur. The disturbances include additive white noise, multiplicative white noise and modeled disturbances with coupling of energy-limited white noise and state signals. The input saturation item of system is approximated by the polytopic bounding method. In order to estimate the modeled disturbances, a novel stochastic saturating disturbance observer (SSDO) is designed. The CADC scheme is presented by integrating SSDO with convex hull expression of saturated linear feedback law, such that the superior anti-disturbance performance to be achieved while overcoming the effects of input saturation. Finally, the validity and usability of the developed scheme are testified by the numerical simulation and practical application example.

A new control design for a morphing UAV based on disturbance observer and command filtered backstepping techniques

Morphing unmanned aerial vehicle (UAV) can manipulate its shape for excellent flight performance under different conditions. The most research of the morphing UAV focuses on modeling. However, the issues including nonlinear characteristics, strong couplings, and mismatched disturbances are inevitable, which can lead to a great challenge in controller design. In this paper, a composite anti-disturbance controller is developed for morphing UAV to achieve enhanced flight performance under multiple sources of disturbances. In the inner loop, a nonlinear disturbance observer (DO) is constructed to estimate the inertial forces and moment; while in the outer loop, the command filtered backstepping (CFBS) method is adopted to guarantee the stability of the closed-loop system. The system outputs can promptly track reference signals in the morphing process of the UAV. The novelty is that the disturbance estimations are added into the control laws to compensate the mismatched disturbances. When comparing to the previous methods, the control scheme presented in this study can significantly improve the performance of anti-disturbance. Finally, the effectiveness of the proposed method is illustrated by numerical simulations.

Composite anti-disturbance control for uncertain Markovian jump systems with actuator saturation based disturbance observer and adaptive neural network

This paper studies the problem of composite control for a class of uncertain Markovian jump systems (MJSs) with partial known transition rates, multiple disturbances and actuator saturation. Compared with the existing results, a novel robust composite control scheme is put forward by virtue of adaptive neural network technique. For MJSs, the partial unknown information on transition rates and the actuator saturation influence the design of disturbance observer and the robust H∞ controller. Firstly, without taking account of external disturbances, the network reconstruction error and saturation, a novel robust adaptive control strategy is established to ensure that all the signals of the closed-loop system are asymptotically bounded in mean square. Secondly, the solvability condition for ensuring the robust H∞ performance is given by using a modified adaptive law, where the saturation is treated as a disturbance-like signal. Finally, the simulations for a numerical example and an application example are performed to validate the effectiveness of the proposed results.

Composite antidisturbance control for nonlinear systems via nonlinear disturbance observer and dissipative control

SummaryThis paper investigates the design problem of composite antidisturbance control for a class of nonlinear systems with multiple disturbances. First, a novel nonlinear disturbance observer‐based control scheme is constructed to estimate and compensate the disturbance modeled by the nonlinear exosystem. Then, by combining the dissipative control theory, a linear matrix inequality‐based design method of composite antidisturbance control is developed such that the augmented system is exponentially stable in the absence of unmodeled disturbances, and is dissipative in the presence of unmodeled disturbances. In this case, the original closed‐loop system is exponentially stable in the presence of modeled disturbances. Subsequently, two special cases of composite antidisturbance control are derived with H∞ performance and passivity, respectively. Finally, the proposed method is applied to control A4D aircraft to show its effectiveness.

Disturbance Attenuation and Rejection for Nonlinear Uncertain Switched Systems Subject to Input Saturation

This paper studies the problem of disturbance attenuation and rejection for switched systems with nonlinear uncertainty and input saturation via composite anti-disturbance control technique, in which the exosystem-generated disturbance and H 2 -norm-bounded disturbance are considered. For switched systems, the switching law and input saturation increase the difficulty for the design of the disturbance observer and the composite control scheme. A switching disturbance observer is designed to obtain the estimation of the matched disturbance, and a novel switching composite controller is further constructed based on the estimated value. By proposing a state-dependent switching law and utilizing the multiple Lyapunov function technology, the criteria are presented to ensure the local asymptotic stability with an H ∞ performance level for the closed-loop system. Furthermore, two optimal algorithms of the design of the controller are put forward to maximize the estimation of the domain of attraction of the closed-loop and the upper bound on the H 2 -norm of the disturbance, respectively. The effectiveness of the proposed technique is illustrated via the numerical examples.

Anti-disturbance control based on disturbance observer for nonlinear systems with bounded disturbances

A composite anti-disturbance control problem for a class of nonlinear systems is studied in this paper. There are two types of disturbances in the systems, one is the matched disturbance with bounded variation rate, the other is the unmatched time-varying disturbances. A nonlinear disturbance observer is designed to estimate the matched disturbances, which can be presented separately from the controller design. By integrating DOBC with back-stepping method, a composite DOBC and back-stepping controller is proposed, and the disturbance estimations are introduced into the design of virtual control laws to compensate the unmatched disturbances. In addition, it is proved that all the states in the closed-loop system are uniformly ultimate bounded (UUB). Finally, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method.

Non-linear disturbance observer-based adaptive composite anti-disturbance control for non-linear systems with dynamic non-harmonic multisource disturbances

In this paper, an adaptive composite anti-disturbance control structure is constructed for a class of non-linear systems with dynamic non-harmonic multisource disturbances. The key point of this paper is that a kind of non-harmonic disturbance, which has non-linear internal dynamics and complex features, is involved. A non-linear exogenous system is employed to describe the dynamic non-harmonic disturbances and several useful assumptions are introduced. By introducing a non-linear damping term, a novel adaptive non-linear disturbance observer is constructed. Based on the disturbance/uncertainty estimation and attenuation (DUEA) schemes, a composite anti-disturbance control structure is synthesized. Meanwhile, a new sufficient condition is derived and the stability of the closed-loop system is proved. Several illustrative examples are employed to demonstrate the effectiveness of the proposed method.

Composite anti‐disturbance attitude and vibration control for flexible spacecraft

This study is concerned with the problem of composite anti-disturbance control for attitude manoeuvre and vibration reduction in the presence of external disturbances. By employing finite-time integral sliding manifold, a novel finite-time integral sliding mode disturbance observer is constructed to estimate the lumped disturbances in finite time, where the lumped disturbances include external disturbances and coupling terms between system states and flexible modal. Based on the estimation values, a composite anti-disturbance controller is proposed via backstepping method. Simulation results are employed to demonstrate the effectiveness of the proposed technique.

Anti-disturbance control for time-varying delay Markovian jump nonlinear systems with multiple disturbances

ABSTRACTIn this paper, the problem of composite anti-disturbance resilient control is addressed for time-varying delay Markovian jump nonlinear systems with multiple disturbances. The disturbances are assumed to include two parts: the first one in the input channel is described by an external system with perturbations; the second one is supposed to be bounded H2 norm. By combining disturbance observer and L2–L∞ control method, the disturbances are attenuated and rejected, simultaneously, and the desired dynamic performance can be obtained for time-varying delay Markovian jump nonlinear systems. Moreover, the gains of the resilient controller and the observer are acquired by applying linear matrix inequalities (LMIs) technology. Finally, an application example is presented to show the effectiveness of the proposed approach.

Stochastic disturbance observer-based adaptive anti-disturbance control for non-linear systems with stochastic non-harmonic multiple disturbances

In this paper, the problem of anti-disturbance control is studied for non-linear systems with stochastic multiple disturbances. The multiple disturbances include two types: one is the stochastic harmonic disturbance and the other non-harmonic noise generated by a linear stochastic exogenous system. An adaptive stochastic disturbance observer (ASDO) is constructed to estimate both the two aforementioned disturbances. Combining the disturbance estimation with a conventional state feedback control law, a composite anti-disturbance control scheme is constructed such that the closed-loop system is stochastically stable, and different types of disturbances may be attenuated and rejected. By using the Lyapunov function method and linear matrix inequalities technique, sufficient conditions for the stochastic stability of the closed-loop system are established. Moreover, an adaptive stochastic extended state observer (ASESO) is proposed for the output feedback case. Finally, an application example is provided to demonstrate the effectiveness of the proposed method.

Sliding mode friction observer based control for flexible spacecraft with reaction wheel

A novel composite anti-disturbance control scheme is proposed for attitude control system (ACS) of flexible spacecraft with the reaction wheel friction. The proposed control scheme can overcome the performance degradation of controller under the condition of reaction wheel friction and flexible appendage vibration. First, the dynamic model of the flexible spacecraft is modelled, including disturbance torque of the reaction wheel. A sliding mode friction observer is designed to estimate the reaction wheel friction torque for feed-forward compensation. Then, a flexible appendage vibration observer is constructed to estimate and compensate for the flexible appendage vibration. Finally, an H ∞ controller is adopted to attenuate the estimation error and other bounded disturbances, such as the environment disturbance. Simulations on the ACS of a flexible spacecraft demonstrate the robustness and effectiveness of the proposed method.

Composite adaptive anti-disturbance control for MIMO nonlinearly parameterized systems with mismatched general periodic disturbances

ABSTRACTIn this paper, the problem of anti-disturbance control for a class of multi-input and multi-output (MIMO) nonlinearly parameterized systems with mismatched general periodic disturbances is investigated via a composite adaptive anti-disturbance control scheme. The composite adaptive anti-disturbance control method is presented by using disturbance observer technique, back-stepping method and adaptive control approach. A novel disturbance observer is designed to estimate the disturbances generated by a linear system with nonlinear output function. Rigorous stability analysis for the augmented closed-loop system is developed by direct Lyapunov stability theory. It is shown that the system outputs asymptotically converge to zero in the presence of mismatched general periodic disturbances. Finally, a simulation example is given to demonstrate the effectiveness of the proposed method.

Constrained anti-disturbance control for a quadrotor based on differential flatness

ABSTRACTThe classical control design based on linearised model is widely used in practice even to those inherently nonlinear systems. Although linear design techniques are relatively mature and enjoy the simple structure in implementations, they can be prone to misbehaviour and failure when the system state is far away from the operating point. To avoid the drawbacks and exploit the advantages of linear design methods while tackling the system nonlinearity, a hybrid control structure is developed in this paper. First, the model predictive control is used to impose states and inputs constraints on the linearised model, which makes the linearisation satisfy the small-perturbation requirement and reduces the bound of linearisation error. On the other hand, a combination of disturbance observer-based control and H∞ control, called composite hierarchical anti-disturbance control, is constructed for the linear model to provide robustness against multiple disturbances. The constrained reference states and inputs generated by the outer-loop model predictive controller are asymptotically tracked by the inner-loop composite anti-disturbance controller. To demonstrate the performance of the proposed framework, a case study on quadrotor is conducted.

Composite anti‐disturbance control for switched systems via mixed state‐dependent and time‐driven switching

This study is concerned with the problem of composite anti-disturbance control for switched linear systems with multiple disturbances. The authors' aim is to construct a disturbance observer to estimate the disturbance generated by an exogenous system, then design a composite controller based on the disturbance observer and a mixed state-dependent and time-driven switching law, such that the closed-loop system is internally stable, and different types of disturbances are attenuated and rejected. First, a mixed switching law is designed, which guarantees a dwell time even when all subsystems are unstable. Then, a sufficient condition ensuring the solvability of the composite anti-disturbance control problem is presented via multiple Lyapunov functions. Finally, the effectiveness of the proposed control design scheme is illustrated by its application to an aero-engine, which cannot be handled by the existing approaches.

Continuous finite time control for static var compensator with mismatched disturbances

In this paper, the composite anti-disturbance control problem is addressed for a single machine bus system with static var compensator. A finite time disturbance observer is designed to estimate the external disturbances. Then based on disturbance estimation value, a continuous finite time anti-disturbance controller is proposed. It is proved that the proposed scheme can guarantee that the system outputs converge to zero in finite time. Finally, a simulation result is presented to demonstrate the effectiveness of the developed method.

Neural Network-Based DOBC for a Class of Nonlinear Systems With Unmatched Disturbances.

In this brief, the problem of composite anti-disturbance tracking control for a class of strict-feedback systems with unmatched unknown nonlinear functions and external disturbances is investigated. A disturbance-observer-based control (DOBC) in combination with a neural network scheme and back-stepping method is developed to achieve a composite anti-disturbance controller design that provides guaranteed performance. In the proposed method, a conventional disturbance observer and a radial basis function neural network (RBFNN) are combined into a new disturbance observer to estimate the unmatched disturbances. As compared with conventional DOBC methods, the primary merit of the proposed method is that the unknown nonlinear functions are approximated using the RBFNN technique, and not regarded as part of the disturbances or estimated by a conventional disturbance observer. Hence, the proposed method can obtain higher control accuracy than the conventional DOBC methods. This advantage is validated by simulation studies.