Composite Disturbance Observer Research Articles

Trajectory Tracking Control Based on a Composite Disturbance Observer for Unmanned Autonomous Helicopters under Multiple Disturbances

This paper studies the trajectory tracking anti-disturbance control of unmanned autonomous helicopters (UAHs) under matched disturbances and mismatched ones. Firstly, the six-degrees-of-freedom UAH nonlinear system is simplified via feedback linearization to handle strong coupling, in which the multiple disturbances are composed of modeled disturbances and time-varying bounded ones. Secondly, in order to estimate these disturbances, a new design method of a composite disturbance observer is proposed. On the one hand, for the mismatched disturbances, a normal disturbance observer (DO) combined with a backstepping control are utilized to handle their negative effect. On the other hand, two refined disturbance observers (RDOs) are constructed to estimate the matched disturbances, in which the coupling estimations are involved. Then, by designing two anti-disturbance composite controllers, the boundedness of the tracking errors is guaranteed by using the Lyapunov stability theory. Finally, some numerical simulations are provided to demonstrate the effectiveness and advantage of the proposed control scheme.

Decoupled Active Disturbance Rejection Control for PMSM Drives to Retain Deadbeat Properties Using Composite Disturbance Observer

Decoupled Active Disturbance Rejection Control for PMSM Drives to Retain Deadbeat Properties Using Composite Disturbance Observer

Variable-horizon predictive tracking control for air-breathing hypersonic vehicle based on composite disturbance observer

In this paper, a variable-horizon predictive tracking control (VHPTC) scheme based on composite disturbance observer (CDO) is proposed to investigate the attitude tracking problem for an air-breathing hypersonic vehicle (AHV) subject to external matched and mismatched disturbances. An explicit predictive tracking control term with the variable horizon is employed to reduce the online computation and improve the control performance of the AHV system. To comprehensively suppress the negative influences caused by the matched and mismatched disturbances, a CDO is constructed to estimate the unknown disturbances. Moreover, to further guarantee the stability of the closed-loop system affected by the resulting disturbance estimation error, the auxiliary control term is presented. Combining the predictive tracking control term with the variable horizon, the auxiliary control term, and the disturbance compensation control term obtained by CDO, the entire VHPTC law for the AHV system is obtained. Through the Lyapunov analysis, the rigorously exponential stability of the closed-loop system is ensured by the proposed CDO-based VHPTC scheme. The simulation results demonstrate the effectiveness of the presented strategy for the AHV attitude system.

Neural-Network-Based Adaptive Tracking Control for Nonlinear Multiagent Systems: The Observer Case.

This article focuses on the neural-network (NN)-based adaptive tracking control issue for a class of high-order nonlinear multiagent systems both subjected to the immeasurable state variables and unknown external disturbance. Combining with the radial basis function NNs (RBF NNs), the composite disturbance observer and state observer for each follower are established, respectively. The purpose of this work is to develop NN-based adaptive tracking control schemes such that the output of each follower ultimately tracks that of the leader and all the signals of the closed-loop systems are semiglobally uniformly ultimately bounded by utilizing the backstepping technique. Furthermore, so as to cope with the sparsity of the control resources, the proposed method is extended to the event-triggered case and the adaptive event-triggered tracking control protocol is formulated for nonlinear multiagent systems. Finally, the numerical example is performed to verify the efficacy of the proposed approach.

Adaptive Neural-Network-Based Fault-Tolerant Control for a Flexible String With Composite Disturbance Observer and Input Constraints

We propose an adaptive neural-network-based fault-tolerant control scheme for a flexible string considering the input constraint, actuator gain fault, and external disturbances. First, we utilize a radial basis function neural network to compensate for the actuator gain fault. In addition, an observer is used to handle composite disturbances, including unknown approximation errors and boundary disturbances. Then, an auxiliary system eliminates the effect of the input constraint. By integrating the composite disturbance observer and auxiliary system, adaptive fault-tolerant boundary control is achieved for an uncertain flexible string. Under rigorous Lyapunov stability analysis, the vibration scope of the flexible string is guaranteed to remain within a small compact set. Numerical simulations verify the high control performance of the proposed control scheme.

Distributed DETMs-based internal collision avoidance control for UAV formation with lumped disturbances

This work focuses on the internal collision avoidance control for unmanned aerial vehicle (UAV) formation based on distributed dynamic event-triggered mechanisms (DETMs) and composite disturbance observers. To decrease the transmission rate of the redundant data and alleviate the communication network burden, a method of designing distributed event-triggered mechanisms with dynamic triggering threshold functions is proposed, which are related to tracking errors, triggering errors and consistency errors. By taking the lumped disturbances into account, which include the primary disturbance generated by exogenous system and the secondary disturbance effects from adjacent UAVs, a composite disturbance observer is constructed for each UAV to counteract the negative effects of the unknown disturbances. Moreover, by referring to the prescribed performance control method, a consensus controller, which can avoid the internal collision among the multiple UAVs, is presented for each UAV to achieve the control target. The stability of the closed-loop system can be guaranteed by using the Lyapunov stability theory, along with the gains of controller and observers being represented in explicit forms. Finally, a simulation example regarding six UAVs testifies the availability of the proposed control strategy.

Improved Deadbeat Predictive Current Control of Dual Three-Phase Variable-Flux PMSM Drives With Composite Disturbance Observer

The dual three-phase variable-flux permanent-magnet synchronous motors (VF-PMSM) have received more attention in the variable-speed drive applications since they have advantages of high-efficiency in flux-tuning ability, low current stresses in phase legs and high fault-tolerant capability. The magnetization-state of the permanent magnets in VF-PMSM can be manipulated by the larger <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current pulse. However, the accompanied issues of parameter variation and inherent model uncertainty in magnetization manipulation of VF-PMSM increase the difficulty in parameter tuning for conventional proportional-integral controller, which deteriorates the control performance in current loop. To achieve the high performance of current tracking, an improved deadbeat predictive current control (DPCC) with composite disturbance observer has been proposed for dual three-phase VF-PMSM in this article. In the proposed composite disturbance observer, the generalized proportional--integral observer (GPIO) is employed for tracking the time-varying disturbance, and the sliding-mode observer is designed to reduce the settling time caused by the high-order GPIO for the improvement of the system dynamics. The analysis about the bandwidth-parameterized method has been presented for tuning the coefficients of the composite observer. The experimental results are presented to verify the validity of the proposed DPCC with composite disturbance observer for dual three-phase VF-PMSM drives under model uncertainty and different operating conditions.

Attitude stabilization of slosh-coupled satellite with flexible appendage

In this paper, a robust control scheme is proposed for flexible satellite attitude stabilization in the presence of multiple disturbances including the disturbances caused by flexible appendages with the sloshing dynamics of the liquid propellant and external disturbances from space environment. A composite control scheme is designed by combining a composite disturbance observer (CDO) with feed-forward controller. First, a CDO is constructed to estimate the lumped disturbances, where the lumped disturbances in the system are equivalent into two parts: a slow varying disturbance and periodic disturbance. Then a PD controller is adopted to stabilize the system and restrain the residue disturbance. Finally, the simulation results for flexible satellite verify that the proposed method can make the satellite asymptotically stable and demonstrate the effectiveness of the proposed scheme.

Design of Composite Disturbance Observer and Continuous Terminal Sliding Mode Control for Piezoelectric Nanopositioning Stage

The nonlinearities of piezoelectric actuators and external disturbances of the piezoelectric nanopositioning stage impose great, undesirable influences on the positioning accuracy of nanopositioning stage systems. This paper considers nonlinearities and external disturbances as a lumped disturbance and designs a composite control strategy for the piezoelectric nanopositioning stage to realize ultra-high precision motion control. The proposed strategy contains a composite disturbance observer and a continuous terminal sliding mode controller. The composite disturbance observer can estimate both periodic and aperiodic disturbances so that the composite control strategy can deal with the disturbances with high accuracy. Meanwhile, the continuous terminal sliding mode control is employed to eliminate the chattering phenomenon and speed up the convergence rate. The simulation and experiment results show that the composite control strategy achieves accurate estimation of different forms of disturbances and excellent tracking performance.

The composite-disturbance-observer based stochastic model predictive control for spacecrafts under multi-source disturbances

In this paper, the attitude control problem of the spacecraft system under input/state constraints and multi-source disturbances is investigated. A novel estimation method, composite-disturbance-observer (CDO), is proposed to provide an estimate for both modeled and unmodeled disturbances in an online manner. Based on the estimates provided by the CDO, the composite stochastic model predictive control (C-SMPC) scheme is designed for attitude control. The recursive feasibility of the C-SMPC method is guaranteed by reformulating the state and input constraints. Furthermore, the sufficient conditions are established to guarantee the stability of the overall closed-loop system. Finally, the simulation on the attitude control of the spacecraft is conducted to verify the effectiveness of the proposed method.

Fully distributed consensus control for a class of disturbed second-order multi-agent systems with directed networks

In this paper, the distributed consensus control problem is considered for a class of disturbed second-order multi-agent systems (MASs) with directed networks. Both leaderless and tracking cases are investigated. For the leaderless consensus problem, each agent is assumed to be affected by local disturbances generated by exosystems. Modeling error is assumed to exist in each local exosystem model. Different from existing works, a local composite disturbance observer is proposed, with which the exact states of the local disturbances can be well estimated asymptotically. Accordingly, the fully distributed leaderless consensus problem can be solved. For the tracking problem, the dynamics of the leader is assumed to be linear with respect to its state variables and the coefficient matrices are unknown to all the followers. Each follower is affected by disturbances generated by exosystems. A class of distributed parameter estimation algorithms is proposed to handle the unknown coefficient matrices in the dynamics of the leader, with which, the fully distributed tracking problem can be further solved. Finally, some simulation examples are given to verify correctness of the theoretical results.

Disturbance observer-based composite neural learning path following control of underactuated ships subject to input saturation

This paper investigates the constrained waypoints-based path following control problem of underactuated ships in the presence of the actuator saturation and the unknown disturbance. An improved composite neural learning control algorithm is proposed by using the command filter and the robust neural damping techniques. In the proposed algorithm, the dynamic auxiliary system is established to generate the saturation error compensating (SEC) signal, which is used to modify the error dynamics such that the actuator saturation constraint is tackled. The neural networks are employed to deal with the model uncertainty, and the corresponding compensating effects are improved further by designing the simplified serial-parallel estimation model (SPEM). By constructing the robust neural damping term, only two adaptive parameters are required to be updated online. That leads to a smaller computational application burden. Furthermore, the composite disturbance observer (CDOB) is developed by fusion of the prediction error and the compensated tracking one, where the unknown disturbance can be estimated accurately and compensated effectively. In addition, considerable efforts are made to obtain the semi-global uniformly ultimately bounded (SGUUB) stability of the closed-loop system. The convictive experiments are performed to verify the effectiveness and superiority of the proposed algorithm.

Active Control Design Approach for Roll/Yaw Attitude Satellite Stabilization with Flexible Vibration

The new communication satellites are tricky in a control point of view, since their conceptions have several sources of flexibilities: solar arrays and antennas which can be very large with respect to the main body and may lead to degradation of the performance of spacecraft attitude. This work aims to present a composite disturbance observer based controller (CDOBC) for flexible spacecraft is proposed to enhance the disturbance attenuation performance. The controller contains a composite disturbance observer (CDO) and a state feedback controller (SFC) plus feed-forward. First, the disturbance in the system is equivalent to two parts: slow varying disturbance and periodic disturbance control scheme. Thus, the disturbance can be modelled by a state equation and estimated by CDO according to the attitude rates. Then, the feed-forward is adopted to compensate the estimated disturbance and the state feedback controller is adopted to stabilize the system and restrain the residue disturbance. The simulation results demonstrate the effectiveness of the proposed method.

Anti-Disturbance Output Feedback Tracking Control for Switched Stochastic Systems With Multiple Disturbances via Mode-Dependent Average Time Method

The anti-disturbance output feedback tracking control problem is addressed for switched stochastic systems with multiple disturbances in this article. To deal with unknown disturbances and unmeasurable states, composite disturbance observer and state observer are designed simultaneously. Then, an output feedback tracking controller is designed based on outputs of two observers. By employing multiple Lyapunov function method, some sufficient conditions are given to analyse the mean square exponential stability with weighted H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> performance for the closed-loop system. Furthermore, the controller and observer gains are solved by linear matrix inequalities. At last, the validity of the presented scheme is demonstrated via two examples.

A composite disturbance observer and H∞ control scheme for flexible spacecraft with measurement delay and input delay

In this paper, the attitude control algorithm of flexible spacecraft with unknown measurement delay and input delay based on disturbance observer is designed. The influence of measurement delay and input delay on the attitude control system and disturbance observer is analyzed. The disturbance estimation error equation is transformed into a differential system with a pure delay. Then, the observer gain is chosen based on the 3/2 stability theorem to ensure the stability and disturbance attenuation performance of the pure delay system. Next, the controller gain is designed based on the Linear Matrix Inequality (LMI) approach to guarantee the stability of the composite system and achieve H∞ performance with two additive delays. The simulation results show that the proposed method can improve the anti-disturbance ability of the attitude control system.

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.

Robust Consensus of Multi-Agent Systems with Uncertain Exogenous Disturbances

The objective of this paper is to investigate the consensus of the multi-agent systems with nonlinear coupling function and external disturbances. The disturbance includes two parts, one part is supposed to be generated by an exogenous system, which is not required to be neutrally stable as in the output regulation theory, the other part is the modeling uncertainty in the exogenous disturbance system. A novel composite disturbance observer based control (DOBC) and H∞ control scheme is presented so that the disturbance with the exogenous system can be estimated and compensated and the consensus of the multi-agent systems with fixed and switching graph can be reached by using H∞ control law. Simulations demonstrate the advantages of the proposed DOBC and H∞ control scheme.