Decentralized Output Feedback Research Articles

Decentralized dynamic output feedback control for affine fuzzy large-scale systems with measurement errors

This paper investigates the decentralized output feedback control problem for affine fuzzy large-scale systems with unknown interconnections. A decentralized piecewise dynamic output feedback controller is constructed, and the measurement errors between actual outputs and measured outputs are considered in control synthesis. By introducing the S-procedure and a cyclic-small-gain condition, novel controller design conditions in terms of linear matrix inequalities (LMIs) are derived, which allow for reducing the worst case peak output due to measurement errors with satisfying an L∞-norm constraint. Finally, two examples are given to illustrate the effectiveness and superiority of the new results.

A generalized robust decentralized control methodology for a class of interconnected nonlinear systems subject to uncertainties and disturbances

This paper studies the problem of robust decentralized control for a class of large-scale interconnected systems subject to uncertainties and disturbances via a generalized output feedback control method. First, a generalized extended state observer is constructed separately for each subsystem with less dependence of the precise system information and structure. Second, an explicit formula of the easy-transplantable decentralized robust control law is presented with an active compensation of disturbance. Moreover, the proposed methodology is extended to the sampled-data control case without any additional assumptions and hence will ease the practical implementations. It is shown that by a delicate analysis procedure of both continuous-time and hybrid scenarios, the closed-loop system can be rendered semi-globally asymptotically stable only using decentralized output feedback anti-disturbance controller. Numerical simulations show the efficiency of the proposed method.

Zero Assignment Problem in RLC Networks

The paper deals with the problem of zero assignment in RLC networks by selection of appropriate values for the non- dynamical elements, the resistors. For a certain family of network redesign problems by the additive perturbations may be described as diagonal perturbations and such modifications are considered here. This problem belongs to the family of DAP problems (Determinantal Assignment Problem) and has common features with the pole assignment problem by decentralized output feedback and the zero assignment problem via structured additive perturbations. We demonstrate that the sufficient condition for generic zero assignment by selecting the resistors holds true. This condition is related to the rank of the differential of the related map and holds true generically when the degrees of freedom of the matrix of resistors exceeds the number of frequencies to be assigned (n > p + q). Using this result, we show through a generic example that the sufficient condition for the general zero assignment problems in RLC networks is satisfied and thus, zero assignment can be achieved via resistor determination.

Selection of Decentralised Control Structures: Structural Methodologies and Diagnostics

The paper aims at formulating an integrated approach for the selection of decentralized control structures using a number of structural criteria aiming at facilitating the design of decentralised control schemes. This requires the selection of decentralisation structure that will allow the generic solvability of a variety of decentralised control problems, such as pole assignment by decentralised output feedback. The approach is based on the use of necessary and sufficient conditions for generic solvability and exact solvability of decentralised control problems. The generic solvability conditions lead to characterisations of inputs and outputs channel partitions. The exact solvability conditions use criteria on avoiding the presence of fixed modes, as well as necessary conditions for pole assignment, expressed in terms of properties of Plϋcker invariants and Markov type matrices. The structural approach provides a classification of desirable input and output partitions based on structural criteria and it is embedded in an overall framework that may involve aspects related to large scale design.

Robust H∞ dynamic output feedback synchronization for complex dynamical networks with disturbances

In this paper, the robust H∞ dynamic output feedback synchronization problem for complex dynamical networks with disturbances is studied. A novel decentralized output feedback control scheme is proposed. For each node, a dynamic output feedback controller which is driven by local relative output measurements is constructed. By introducing the spectral decomposition technique, the closed-loop synchronization error system is proved to be robustly stable with an optimal H∞ disturbance attenuation level. A simulation example of master-slave large scale system verifies the effectiveness of the proposed method.

Decentralized output feedback adaptive NN tracking control of interconnected nonlinear time-delay systems with prescribed performance

This paper studies the decentralized output feedback adaptive NN tracking control problem for interconnected nonlinear time-delay systems with prescribed performance. By using the novel states transformation, the prescribed tracking performance can be guaranteed. Firstly, we design the decentralized filters independent of time delay to estimate the unmeasured state variables. By estimating the bounds of the unknown parameters instead of themselves, it can avoid the over-estimation problem. Then, by using RBF (radial basis function) neural network (NN) to approximate the unavailable time-delay functions, we construct the adaptive neural network output feedback controller with corresponding adaptive laws. It is proved that all the signals of the overall closed-loop systems are ultimately uniformly bounded. Finally, simulation examples are presented to verify the effectiveness of the theoretic results obtained.

Decentralised adaptive output feedback stabilisation for stochastic time-delay systems via LaSalle-Yoshizawa-type theorem

ABSTRACTThis paper deals with the decentralised output feedback stabilisation problem for a class of large-scale stochastic time-delay nonlinear systems. A general theorem is firstly given to guarantee the global existence and uniqueness of the solution for stochastic time-delay systems. In addition, a stochastic version of the well-known LaSalle-Yoshizawa theorem with time-varying delay is initially proposed for the controller design and stability analysis. Then, for a class of large-scale stochastic systems with time-varying delays, totally decentralised adaptive delay-dependent controllers are designed by using K-filter and backstepping approach. Via LaSalle-Yoshizawa-type theorem and constructing a general Lyapunov function, it is shown that all signals in the closed-loop system are bounded almost surely and the solution is almost surely asymptotically stable. Finally, a simulation example is given to illustrate the effectiveness of the results of this paper.

Decentralized load frequency control for two-area interconnected power system

This paper proposes a decentralized output feedback control scheme applied to two-area interconnected power system. Thecontroller synthesis problem is formulated as the scaled H∝ control problem and a new LMI-based algorithm is proposed tocompute the decentralized controller. The proposed controller provides robustness with regard to parametric uncertainties andalso attenuates bounded exogenous disturbances in the sense of L 2-gain. Simulation results clearly show the effectiveness ofdeveloped decentralized output feedback control scheme.

Decentralized Output Feedback Adaptive NN Tracking Control for Time-Delay Stochastic Nonlinear Systems With Prescribed Performance.

This paper studies the dynamic output feedback tracking control problem for stochastic interconnected time-delay systems with the prescribed performance. The subsystems are in the form of triangular structure. First, we design a reduced-order observer independent of time delay to estimate the unmeasured state variables online instead of the traditional full-order observer. Then, a new state transformation is proposed in consideration of the prescribed performance requirement. Using neural network to approximate the composite unknown nonlinear function, the corresponding decentralized output tracking controller is designed. It is strictly proved that the resulting closed-loop system is stable in probability in the sense of uniformly ultimately boundedness and that both transient-state and steady-state performances are preserved. Finally, a simulation example is given, and the result shows the effectiveness of the proposed control design method.

Unstructured quotient fixed modes and decentralised stabilisability

In this paper we derive a sufficient condition for which unstructured decentralised fixed modes (UDFMs) of a LTI system cannot be stabilised by any form of decentralised output feedback controllers. The sufficient condition establishes the link between special UDFMs (SUDFMs) and quotient fixed modes (QFMs). The link between UDFMs and QFMs provides an unequivocal answer, which has up until now eluded researchers, as to why some UDFMs cannot be eliminated by sampled-data controllers. In addition, we use this link to highlight the role system parameter uncertainties can play in shifting stabilisable DFMs to UDMFs or QFMs and vice versa. Numerical examples are presented to illustrate all aspects of the paper.

Output Feedback and Single-Phase Sliding Mode Control for Complex Interconnected Systems

This paper generalized a new sliding mode control (SMC) without reaching phase to solve two important problems in the stability of complex interconnected systems: (1) a decentralized controller that uses only output variables directly and (2) the stability of complex interconnected systems ensured for all time. A new sliding surface is firstly designed to construct a single-phase SMC in which the desired motion is determined from the initial time instant. A new lemma is secondly established for the controller design using only output variables. The proposed single-phase SMC and the decentralized output feedback controller ensure the robust stability of complex interconnected systems from the beginning to the end. One of the key features of the single phase SMC scheme is that reaching time, which is required in most of the existing two phases of SMC approaches to stabilize the interconnected systems, is removed. Finally, a numerical example is used to demonstrate the efficacy of the method.

Decentralized Robust Control for Multi-Machine Power System

This paper proposes a new decentralized output feedback control scheme for three-machine power system. The decentralized controller synthesis problem is formulated as a scaled H∞ control problem, and an LMI-based algorithm is developed to synthesize the decentralized controller. The proposed controller provides robustness with regard to parametric uncertainties and also attenuates bounded exogenous disturbances in the sense of L2-gain. Simulation results clearly show the effectiveness of the developed decentralized output feedback control scheme.

Adaptive Output Feedback Sliding Mode Control for Complex Interconnected Time-Delay Systems

We extend the decentralized output feedback sliding mode control (SMC) scheme to stabilize a class of complex interconnected time-delay systems. First, sufficient conditions in terms of linear matrix inequalities are derived such that the equivalent reduced-order system in the sliding mode is asymptotically stable. Second, based on a new lemma, a decentralized adaptive sliding mode controller is designed to guarantee the finite time reachability of the system states by using output feedback only. The advantage of the proposed method is that two major assumptions, which are required in most existing SMC approaches, are both released. These assumptions are (1) disturbances are bounded by a known function of outputs and (2) the sliding matrix satisfies a matrix equation that guarantees the sliding mode. Finally, a numerical example is used to demonstrate the efficacy of the method.

Decentralized Output Feedback Protocol for Consensus Control of a Class of Nonlinear Dynamics Networks

AbstractThis paper studies the consensus control for multi‐agent systems with nonlinear functions satisfying the sector condition. To achieve consensus, we design a distributed output feedback protocol with an undetermined system matrix, and derive some conditions in terms of linear matrix inequalities (LMIs) to guarantee consensus of all agents' states. Furthermore, by solving three LMIs, the system matrix of the output feedback protocol is designed. Finally, we provide a simulation to show the effectiveness of the proposed consensus protocol.

Adaptive fuzzy output feedback dynamic surface control of interconnected nonlinear pure-feedback systems.

In this paper, an adaptive fuzzy decentralized output feedback control design is presented for a class of interconnected nonlinear pure-feedback systems. The considered nonlinear systems contain unknown nonlinear uncertainties and the states are not necessary to be measured directly. Fuzzy logic systems are employed to approximate the unknown nonlinear functions, and then a fuzzy state observer is designed and the estimations of the immeasurable state variables are obtained. Based on the adaptive backstepping dynamic surface control design technique, an adaptive fuzzy decentralized output feedback control scheme is developed. It is proved that all the variables of the resulting closed-loop system are semi-globally uniformly ultimately bounded, and also that the observer and tracking errors are guaranteed to converge to a small neighborhood of the origin. Some simulation results and comparisons with the existing results are provided to illustrate the effectiveness and merits of the proposed approach.

Robustness studies of sensor faults and noises for semi-active control strategies using large-scale magnetorheological dampers

This paper presents comparative studies for various sensor faults and noise effects on the performance of several recently proposed semi-active control algorithms for the control of large-scale magnetorheological dampers. Sensor faults or noises due to various environmental factors and long-term deteriorations may cause degradations in the performance of the control system. In this paper, the authors have carried out an in-depth literature review of the sensor fault or malfunction and noise problems, diagnostic methods and compensation approaches applicable to semi-active control algorithms. For three recently developed semi-active controllers, namely clipped optimal control, decentralized output feedback polynomial control and Lyapunov controller, an extensive study has been carried out on the robustness of these controllers during sensor faults and noise effects. Based on this research, a new real-time qualitative model-based sensor fault detection and diagnosis (RMSFDD) method has been proposed. This novel RMSFDD method shows a good performance during diverse sensor fault types in semi-active control with a real-time application without any training and heavy computational cost.

Performance Validations of Semiactive Controllers on Large-Scale Moment-Resisting Frame Equipped with 200-kN MR Damper Using Real-Time Hybrid Simulations

AbstractMagnetorheological dampers (MR) have the promising ability to mitigate seismic hazard for structures because of their adaptive energy dissipation characteristics and low power requirements that can be met using standby batteries. These attractive characterstics of advanced damping devices, such as MR dampers, are important for achieving the goals of performance-based infrastucture designs. This paper validates the performances of four semiactive control algorithms for the control of a large-scale realistic moment-resisting frame using a large-scale 200-kN MR damper. To conduct this test, a large-scale damper-braced steel frame was designed and fabricated. Four semiactive controllers, namely (1) passive on, (2) clipped optimal controller, (3) decentralized output feedback polynomial controller, and (4) Lyapunov stability based controller, were designed for this frame. Real-time hybrid simulations (RTHS) were carried out for these controllers using three recorded earthquakes. The comparative perform...

Adaptive fuzzy decentralised output feedback control of pure‐feedback large‐scale stochastic non‐linear systems with unknown dead zone

In this study, a robust adaptive fuzzy decentralised backstepping output feedback control approach is proposed for a class of uncertain non-linear stochastic large-scale systems in pure-feedback form. The non-linear large-scale systems under study have unknown non-linear functions, unknown dead-zone and immeasurable states. Fuzzy logic systems are used to approximate the unknown non-linear functions, and a K-filters state observer is designed for estimating the unmeasured states. Based on the information of the bounds of the dead-zone slopes as well as treating the time-varying inputs coefficients as a system uncertainty, a robust adaptive fuzzy decentralised output feedback control approach is constructed via the backstepping recursive design technique. It is shown that the proposed control approach can guarantee that all the signals of the resulting closed-loop system are semi-globally uniformly ultimately bounded in probability, and the observer errors and the output of the system can be regulated to a small neighbourhood of the origin by choosing design parameters appropriately. A simulation example is provided to show the effectiveness of the proposed approach.

Delay-independent decentralised output feedback control for large-scale systems with nonlinear interconnections

In this paper, a stabilisation problem for a class of large-scale systems with nonlinear interconnections is considered. All the uncertainties are nonlinear and are subject to the effects of time delay. A decentralised static output feedback variable structure control is synthesised and the stability of the corresponding closed-loop system is analysed based on the Lyapunov Razumikhin approach. A set of conditions is developed to guarantee that the large-scale interconnected system is stabilised uniformly asymptotically. Further study shows that the conservatism can be reduced by employing additive controllers if the known interconnections are separated into matched and mismatched parts. It is not required that the subsystems are square. The designed controller is independent of time delay and thus it does not require memory. Simulation results show the effectiveness of the proposed approach.

Application of Person-by-Person Equilibrium and Performance-Measure Statistics to Distributed Control of Uncertain Stochastic Large-Scale Systems with Time Delays

This paper presents a distributed control design for a class of interconnected linear systems with Markovian jumps, parametric uncertainties and time delays in both system states and control actuations. The switching of a countable number of modes associated with constituent systems is encapsulated by appropriate probability transitions. The parameter uncertainties are considered to be unknown but norm bounded. Analysis of time-delay systems is supported by Pade approximations of the first order. A general framework of multi-person nonzero-sum stochastic differential games is leveraged for distributed decision making with performance risk-aversion. Towards performance risk-aversion and reliability, self-directed controllers and/or decision makers are now capable of effectively incorporating risk-averse attitudes via performance-measure statistics into person-by-person equilibrium decisions with decentralized output feedback for distributed interactions.