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Control Theory & Applications, IET

Issue 6 • Date April 17 2014

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Displaying Results 1 - 8 of 8
  • Linear quadratic Gaussian control for linear time-delay systems

    Publication Year: 2014 , Page(s): 375 - 383
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (258 KB)  

    This study investigates a separation principle for the H2 control of time-delay systems with partial observations. The authors first consider the linear quadratic regulation problem for time-delay systems. Based on the dynamic programming technique, the solution to the controller is given in terms of a backward partial difference Riccati equation. Then the estimation problem is investigated for linear discrete-time systems in the presence of time-delays. By employing the innovation analysis approach, the linear minimum-mean-square error (LMMSE) estimator is developed in terms of a forward partial difference Riccati equation. The Riccati equation is of the same dimension as the plant. Therefore compared with the conventional augmented approach, the presented approach greatly lessens the computational demand when the delay is large. Finally, they show that the separation principle holds in the following sense: an optimal controller can be obtained from two parts, one associated with the optimal control problem when state variable is available, and the other one associated with the LMMSE estimation problem. View full abstract»

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  • Globally optimal real-time distributed fusion of multi-channel observation systems

    Publication Year: 2014 , Page(s): 384 - 388
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (282 KB)  

    A globally optimal real-time distributed fusion algorithm is discussed for multi-channel observation systems. The performance of the fusion is equal to that of centralised Kalman filtering. Different from the existing one based on information filters, the algorithm uses the projection theorem in Hilbert space according to First-Come-First-Serve principle. Local estimates are instantly fused with arrival of local information at fusion centre. Meantime, a real-time strategy is presented to balance the performance and the speed of fusion. Therefore the algorithm is flexible and has the practical benefits. View full abstract»

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  • Consensus of descriptor multi-agent systems via dynamic compensators

    Publication Year: 2014 , Page(s): 389 - 398
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (538 KB)  

    This study deals with the consensus problem via dynamic output feedback (dynamic compensator) for descriptor (singular) multi-agent systems with fixed topologies and agents described by general linear systems. Only output information of each agent can be delivered from its neighbour agents. Based on graph, algebra and descriptor linear system theory, the necessary and sufficient conditions are proposed for the existence of dynamic compensators solving the considered problem. The given conditions depend on both the topologies within descriptor multi-agent systems and the structure properties of each agent dynamics. According to non-zero eigenvalues of the Laplacian matrix of the weighted digraph are the same or different, two consensus algorithms via dynamic compensators are proposed, respectively. The provided examples demonstrate the effectiveness of the proposed consensus algorithms. View full abstract»

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  • Higher-order sliding mode observer for estimation of tyre friction in ground vehicles

    Publication Year: 2014 , Page(s): 399 - 408
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (659 KB)  

    The estimation of friction coefficient for a vehicle when it traverses on different surfaces has been an important issue. In this work, the longitudinal vehicle dynamics, the torsional tyre dynamics and the non-linear LuGre friction dynamics are integrated to model the quarter vehicle dynamics. The road adhesion coefficient in the vehicle dynamics is unknown and varies with the contact surface. To address this issue, the authors consider a class of non-linear uncertain systems that covers the vehicle dynamics and develop a higher-order sliding mode observer based on supertwisting algorithm for state and unknown input estimations. Under Lipschitz conditions for the non-linear functions, the convergence of the estimation error is established. By estimating the road adhesion coefficient, the coefficient of friction can be estimated. Simulation results demonstrate the effectiveness of the proposed observer for state and unknown input estimation. View full abstract»

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  • Force control of semi-active valve lag dampers for vibration reduction in helicopters

    Publication Year: 2014 , Page(s): 409 - 419
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1443 KB)  

    This study considers the design of a closed-loop force-tracking system for a semi-active damper, designed to be used to reduce in-plane vibrations caused by helicopter rotor blades during steady-state forward flight conditions. The study describes the development of the control law and includes details of (i) how the initial mathematical model of the system is adapted for controller design; (ii) how a non-linear dynamic inversion (NDI) control law is modified into a form suitable for implementation; and (iii) how the free parameters in the NDI controller can be optimised for various different operational modes. The success of the approach is demonstrated through both force-tracking simulations and also more comprehensive tests in which the controller is incorporated into a large-scale vibration simulation of the AgustaWestland 101 helicopter. The results show that the NDI-based controller can provide a satisfactory level of performance and hence greatly assist in the reduction of unwanted vibrations. View full abstract»

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  • Prescribed performance fuzzy adaptive fault-tolerant control of non-linear systems with actuator faults

    Publication Year: 2014 , Page(s): 420 - 431
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (707 KB)  

    This study investigates the adaptive fuzzy fault-tolerant control (FTC) problem for a class of uncertain non-linear strict-feedback systems with unmeasured states. The considered non-linear systems contain unknown continuous functions and do not satisfy the matching condition. The actuator failures under study are types of both abrupt faults and lock-in-place and loss of effectiveness. The fuzzy logic systems are employed to approximate the unknown continuous functions, and a fuzzy state observer is developed and the unmeasured states are obtained. Under the framework of the backstepping design technique and incorporated by the dynamic surface control approach and predefined performance bounds, an adaptive fuzzy FTC method has been presented. From the Lyapunov stability analysis, it is shown that all the signals of the resulting closed-loop system are bounded and the tracking error surfaces remain within the prescribed performance bounds in the presence of unknown non-linear actuator faults. The simulation results and comparisons with the previous methods indicate the effectiveness of the proposed adaptive fuzzy FTC. View full abstract»

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  • Leader-following consensus of non-linear multi-agent systems with jointly connected topology

    Publication Year: 2014 , Page(s): 432 - 440
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (565 KB)  

    The leader-following consensus of non-linear multi-agent systems is investigated in this study. The authors further study this problem without the assumption that the topology among followers is connected or fixed. Based on a representative general non-linear model, they address such a leader-following consensus issue from a new perspective and then obtain several basic criteria for the consensus of the non-linear multi-agent system. Simultaneously, the simplified conditions of its corresponding linear multi-agent systems for achieving consensus are derived. Finally, numerical examples are presented to verify the theoretical analysis. View full abstract»

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  • Robust adaptive fault-tolerant control for linear systems with actuator failures and mismatched parameter uncertainties

    Publication Year: 2014 , Page(s): 441 - 449
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (426 KB)  

    In this study, a direct adaptive control scheme is developed to solve the robust fault-tolerant control problem for linear systems with mismatched parameter uncertainties, disturbances and actuator faults including loss of effectiveness, outage and stuck. Although the unparameterisable time-varying stuck faults and the upper bounds of disturbances are unknown, the adaptive laws are proposed to estimate the unknown controller parameters online. Then, by using the information from the adaptive mechanism, a class of robust adaptive state feedback controllers are constructed for automatically compensating the actuator faults, external disturbances and mismatched parameter uncertainties. Moreover, on the basis of Lyapunov stability theory, it is proved that the resulting adaptive closed-loop system can be guaranteed to be asymptotically stable in the presence of actuator faults, disturbances and mismatched parameter uncertainties. Finally, simulation results are presented to illustrate the efficiency of the proposed fault-tolerant design approach. View full abstract»

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