Composite Anti-disturbance Control Research Articles

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.

Composite Adaptive Antidisturbance Control for Discrete-Time Switched System

A novel composite adaptive antidisturbance controller is developed for a class of discrete-time switched system. First, two composite adaptive observers are proposed to estimate the external disturbances and unknown parameters, respectively. Then, based on the estimation values, a composite adaptive antidisturbance controller is constructed, which can guarantee system has a good antidisturbance performance. A solvable sufficient condition is presented by using linear matrix inequalities (LMIs). Finally, a numerical example is shown to demonstrate the effectiveness of the proposed control approach.

Disturbance‐observer‐based‐control and L 2 − L ∞ resilient control for Markovian jump non‐linear systems with multiple disturbances and its application to single robot arm system

In this study, the problem of disturbance-observer-based-control (DOBC) and L 2−L ∞ resilient control for Markovian jump non-linear systems with multiple disturbances is investigated. The disturbances are divided into two parts: one part is produced by an exogenous system and the other part is supposed to lie in the space of L 2[0,∞). A disturbance observer is designed to estimate the first one, and the disturbance estimation is introduced into L 2−L ∞ resilient state feedback control law. Hence, by combining DOBC and L 2−L ∞ control methods, a composite anti-disturbance controller is designed to attenuate and reject two kinds of disturbances. Some sufficient conditions are obtained by using Lyapunov function method and linear matrix inequalities technique. Finally, an application example is given to illustrate the effectiveness of the main algorithm.

Homogeneous Active Disturbance Attenuation for a Perturbed Chain of Integrators

Abstract: Motivated by the homogeneous system theory and its facility in nonlinear control design, a global homogeneous active anti-disturbance method for a class of higher-order nonlinear systems subject to mismatched disturbances is investigated in this paper. Utilizing the flexibility of disturbance soft-estimations with active elimination of the adverse effects caused by disturbances, a homogeneous domination feedback technique is integrated such that a general composite active anti-disturbance control framework is proposed. With a delicate recursive handling procedure of the non-vanishing nonlinearities, the mismatched disturbances are compensated in a novel step-by-step way. A rigorous stability analysis assures the effectiveness of the proposed strategy. Numerical simulation results affirm the control and disturbance rejection performances.

Composite anti-disturbance control for a class of uncertain nonlinear systems via a disturbance observer

A new anti-disturbance control scheme is proposed for a class of nonlinear systems subjected to multi-source disturbances. The uncertain multi-source disturbances are classified into two parts; one is the harmonic and constant disturbance with partial known information, which can be formulated by an exogenous system, and the other consists of unknown time-varying disturbances. The nonlinear disturbance observer (NDO) is constructed to estimate the first kind of disturbance. By integrating the NDO with an adaptive backstepping technique, a novel composite anti-disturbance control scheme is proposed for the nonlinear systems. Then the stability analysis of the closed-loop system is presented. The simulation of a numerical example is given to demonstrate the effectiveness of the proposed results.

A composite anti-disturbance control scheme for attitude stabilization and vibration suppression of flexible spacecrafts

: There exist multiple disturbances resulting from the structural vibrations of flexible appendages, unknown external and internal disturbances, and parameter uncertainties, which affect the attitude control performance seriously. To enhance the disturbance attenuation performance and vibration suppression ability, a composite anti-disturbance control scheme (CADCS) based on disturbance observer is proposed for attitude stabilization and vibration reduction of flexible spacecraft. The CADCS combines a composite disturbance observer (CDO) and a PD controller with feedforward. The multiple disturbances are equivalent to slowly varying disturbance and harmonic disturbance. The CDO can estimate two types of disturbance and compensate for them through feedforward. The PD controller realizes the asymptotic convergence by compensating the disturbance from CDO. The CADCS based on CDO and PD controller is not only simple and easy to realize, but also yields better vibration suppression and anti-disturbance performance. Simulation results of a certain spacecraft demonstrate the effectiveness of the proposed CADCS.

Composite anti-disturbance controller for magnetically suspended control moment gyro subject to mismatched disturbances

To achieve the high-precision control for the hybrid magnetic bearing system in the magnetically suspended control moment gyro under voltage-controlled mode, this paper proposes a composite control approach combining robust control and a state-space disturbance observer. To handle the multiple disturbances, the hierarchical idea is used. The external disturbances are estimated and rejected by a state-space disturbance observer, while the norm-bounded uncertainties are attenuated by robust $${H_\infty }$$ strategy. On the other hand, to counteract the input-mismatched disturbances in the voltage-controlled mode, different equilibrium points are designed for various state variables. That is, the mismatched influence is transferred to the state variable that is not paid much attention. The proposed method exhibits the attractive advantage that it retains the baseline robust controller performance. The effectiveness and superiority of the proposed control method are demonstrated by both simulations and experiments.

High-precision control for double-gimbal magnetically suspended control moment gyro via composite anti-disturbance control

This paper presents a composite anti-disturbance control method for the magnetic bearing system in a double-gimbal magnetically suspended control moment gyro (DGMSCMG) with mismatched disturbances. The proposed method combines a state-space disturbance observer and a robust controller for rejecting and attenuating the external disturbances and model uncertainties. By stabilizing the state variables to different equilibrium points, the mismatched disturbances are transformed to be matched with the control input variable. One novel merit of the proposed method is its ability to deal with the mismatched influence via the disturbance observer. Experimental results conducted on the DGMSCMG system demonstrate the effectiveness of the proposed control strategy.

Composite anti-disturbance control for a discrete-time time-varying delay system with actuator failures based on a switching method and a disturbance observer

The composite anti-disturbance control problem is developed for discrete-time systems with both time-varying delay and multiple disturbances under actuator failures in this paper. First, depending on the information of actuator failures, the system is transformed into a switched system. Then, considering the switched system, the composite controller is designed via a disturbance observer based control and an exponential l2−l∞ control method. A disturbance observer is constructed to estimate the disturbances generated by an exogenous system, and the estimated value is introduced into a memory exponential l2−l∞ state feedback control law, such that, the closed-loop system is asymptotically stable, and different types of disturbances are rejected and attenuated. Third, by resorting to the average dwell time approach and the free-weighting matrix technique, some sufficient criteria for the desired disturbance observer and the state feedback controller are established, and the corresponding solvability conditions using a cone complementarity linearization method are presented. A numerical example is provided to demonstrate the effectiveness of the proposed algorithms finally.

Composite anti-disturbance control for Markovian jump nonlinear systems via disturbance observer

This paper is concerned with the problems of composite disturbance-observer-based control (DOBC) and ℋ∞ control for Markovian jump systems with nonlinearity and multiple disturbances. Our aim is to design a disturbance observer to estimate the disturbance generated by an exogenous system, then construct the control scheme by integrating the output of the disturbance observer with state-feedback control law, such that, the closed-loop system can be guaranteed to be stochastically stable, and different types of disturbances can be attenuated and rejected. By constructing a proper stochastic Lyapunov–Krasovskii functional, sufficient conditions for the existence of the desired observer and the state-feedback controller are established in terms of linear matrix inequalities (LMIs), which can be readily solved by standard numerical software. Finally, a numerical example is provided to show the effectiveness of the proposed approaches.

Composite Antidisturbance Control for a Class of Nonlinear Stochastic Systems via Disturbance Observer

The stabilization problem is investigated in this paper for a class of nonlinear systems with disturbances. The disturbances are supposed to be classified into two types. One type in the input channel is generated by an exogenous system, which can represent the constant or harmonic signals with unknown phase and magnitude. The other type is stochastic disturbance. Two kinds of nonlinear dynamics in the plants are considered, respectively, which correspond to the known and unknown functions. By integrating the disturbance observers with conventional control method, the first type of disturbances can be estimated and rejected. Simultaneously, the desired dynamic performances can be guaranteed. An example is given to show the effectiveness of the proposed scheme.