Showing papers by "Ron J. Patton published in 2012"
TL;DR: In this article, a fault-tolerant control strategy for a wind turbine operating at low wind speed is presented, which uses the proportional multiple integral observer (PMIO) as intermediate block between the system and the controller to provide an estimation of the generator and/or rotor speed sensor(s) faults.
46 citations
TL;DR: An LPV pole-placement approach to friction compensation as an FTC problem and their effect is compensated within a polytope controller system, yielding a robust form of active FTC that is easy to apply to real robot systems.
Abstract: An LPV pole-placement approach to friction compensation as an FTC problemThe concept of combining robust fault estimation within a controller system to achieve active Fault Tolerant Control FTC has been the subject of considerable interest in the recent literature. The current study is motivated by the need to develop model-based FTC schemes for systems that have no unique equilibria and are therefore difficult to linearise. Linear Parameter Varying LPV strategies are well suited to model-based control and fault estimation for such systems. This contribution involves pole-placement within suitable LMI regions, guaranteeing both stability and performance of a multi-fault LPV estimator employed within an FTC structure. The proposed design strategy is illustrated using a nonlinear two-link manipulator system with friction forces acting simultaneously at each joint. The friction forces, regarded as a special case of actuator faults, are estimated and their effect is compensated within a polytope controller system, yielding a robust form of active FTC that is easy to apply to real robot systems.
30 citations
TL;DR: In this article, an active sensor fault-tolerant control (FTC) strategy is proposed to maintain nominal wind turbine controller without change in both fault and fault-free cases.
27 citations
03 Jul 2012
TL;DR: In this paper, a robust fault tolerant control (FTC) strategy is proposed to optimize the wind energy captured by a wind turbine operating at low wind speeds, using an adaptive gain sliding mode control (SMC).
Abstract: This paper presents a new strategy to robust fault tolerant control (FTC) to optimise the wind energy captured by a wind turbine operating at low wind speeds, using an adaptive gain Sliding Mode Control (SMC). In addition to the inherent robustness of SMC against matched model uncertainty, the proposed method involves a robust descriptor observer design that can provide robust simultaneous estimation of states and the “unknown outputs” (sensor faults and noise) in order to guarantee the robustness of the sliding surface against unknown output effects. Moreover, the sliding surface is designed to achieve the required objectives by utilizing the nonlinear flexible two mass model of the variable speed wind turbine. The proposed FTC SMC method is applied to a 5 MW wind turbine benchmark model.
26 citations
TL;DR: A new approach to robust fault tolerant control (FTC) to optimise the wind energy captured by a wind turbine in the low wind speed range of operation, using Sliding Mode Control (SMC).
23 citations
TL;DR: A model of a uniformly distributed osteocyte network has been developed that simulates the signalling through the network to the BLCs based on strain level and provides a unique framework for a broader exploration of the role of osteocyte and bi-directional and asymmetric cell-cell communication in mechanotransduction, and the effects of disruption to that communication.
19 citations
22 Oct 2012
TL;DR: In this paper, a new strategy for wind turbine fault tolerant control (FTC) is presented to optimise the wind energy captured by a wind turbine operating at low wind speeds, which obviates the need for sensor fault residual evaluation and observer switching by using a fuzzy proportional multiple integral observer (PMIO).
Abstract: This paper presents a new strategy for wind turbine fault tolerant control (FTC) to optimise the wind energy captured by a wind turbine operating at low wind speeds. The FTC strategy uses Takagi-Sugeno (T-S) fuzzy observers with state feedback control to maintain nominal wind turbine control without changes in both the fault and fault-free cases. The proposed strategy obviates the need for sensor fault residual evaluation and observer switching by using a fuzzy proportional multiple integral observer (PMIO) to mask i.e. ‘implicitly compensate’ the sensor fault(s) from the controller input and provide good estimation over a wide range of sensor fault scenarios. The proposed FTC method is applied to a 5 MW offshore wind turbine (OWT) benchmark model.
14 citations
01 Sep 2012
TL;DR: In this article, a linear time invariant model-based robust fast adaptive fault estimator with unknown input decoupling is proposed to estimate aircraft elevator oscillatory faults, which depends on system output error dynamics which are de-coupled from the unknown inputs.
Abstract: A linear time invariant model-based robust fast adaptive fault estimator with unknown input decoupling is proposed to estimate aircraft elevator oscillatory faults. Since the robust fast adaptive fault estimator depends on system output error dynamics which are de-coupled from the unknown inputs (modeling uncertainty), the fault estimation signal generated by the designed fault estimator is robust to the estimated unknown inputs. To obtain a fast fault estimation speed, an adaptive fault estimator involves both proportional and integral components. A Lyapunov stability analysis of the robust fast adaptive fault estimator is given and the fault estimator dynamic response is achieved by pole assignment in subregions realized by LMIs. The proposed robust fast adaptive fault estimator is implemented on a high-fidelity nonlinear aircraft model to detect and estimate elevator actuator oscillatory faults.
12 citations
TL;DR: A novel mathematical model of the trabecular bone remodelling cycle, formulated to simulate a remodelling event at a fixed position in the bone, integrating bone removal by osteoclasts and formation by osteoblasts, has potential in the modelling of pathological conditions and the optimisation of the treatment of those conditions.
Abstract: After an initial phase of growth and development, bone undergoes a continuous cycle of repair, renewal and optimisation by a process called remodelling. This paper describes a novel mathematical model of the trabecular bone remodelling cycle. It is essentially formulated to simulate a remodelling event at a fixed position in the bone, integrating bone removal by osteoclasts and formation by osteoblasts. The model is developed to construct the variation in bone thickness at a particular point during the remodelling event, derived from standard bone histomorphometric analyses. The novelties of the approach are the adoption of a predator-prey model to describe the dynamic interaction between osteoclasts and osteoblasts, using a genetic algorithm-based solution; quantitative reconstruction of the bone remodelling cycle; and the introduction of a feedback mechanism in the bone formation activity to co-regulate bone thickness. The application of the model is first demonstrated by using experimental data recorded for normal (healthy) bone remodelling to predict the temporal variation in the number of osteoblasts and osteoclasts. The simulated histomorphometric data and remodelling cycle characteristics compare well with the specified input data. Sensitivity studies then reveal how variations in the model's parameters affect its output; it is hoped that these parameters can be linked to specific biochemical factors in the future. Two sample pathological conditions, hypothyroidism and primary hyperparathyroidism, are examined to demonstrate how the model could be applied more broadly, and, for the first time, the osteoblast and osteoclast populations are predicted for these conditions. Further data are required to fully validate the model's predictive capacity, but this work shows it has potential, especially in the modelling of pathological conditions and the optimisation of the treatment of those conditions.
12 citations
03 Jul 2012
TL;DR: In this article, a fault estimation and compensation for time-varying faults is proposed for non-linear systems. But the fault compensation strategy is illustrated using a nonlinear example of an inverted pendulum which includes Stribeck friction and a loss of effectiveness actuator fault.
Abstract: This paper presents a new approach to active fault-tolerant control for non-linear systems, based on fault estimation and compensation for time-varying faults. The work is a motivation for utilising the extension of the well known so-called fast adaptive fault estimation strategy to non-linear systems via a multiple-model strategy involving Takagi-Sugeno (T-S) fuzzy observer-based estimation and linear model-reference state tracking control. Moreover, the proposed strategy handles the case of unmatched uncertainty in the tracking error dynamics. The stability proof of the appropriate non-linear augmented system is derived via a Lyapunov condition and formulated as an efficient one step Linear Matrix Inequality (LMI) problem constraining the time-varying system eigenvalues to lie within specified regions in the complex plane. The fault compensation strategy is illustrated using a non-linear example of an inverted pendulum which includes Stribeck friction and a loss-of effectiveness actuator fault.*
10 citations
TL;DR: In this article, a linear model-based fault detection and isolation/ diagnosis (FDD) methodology and a corresponding active fault tolerant control (FTC) scheme were implemented on a nonlinear aircraft system directly without control law reconfiguration.
03 Jul 2012
TL;DR: In this article, the robust performance of a novel active fault tolerant control (FTC) approach for a nonlinear UAV during weapon delivery and with a damaged wing, both considered as fault effects, is described.
Abstract: This paper describes the robust performance of a novel active Fault Tolerant Control (FTC) approach for a nonlinear Unmanned Aerial Vehicle (UAV) during weapon delivery and with battled damaged wing, both considered as fault effects. The aircraft dynamics with mass variation and variable wing parameters are introduced and approximately linearized on-line using a dynamic inversion controller based on differential geometry theory. For the linearized system, an active FTC scheme is accomplished via a linear matrix inequality (LMI) approach, based on a simultaneous state/faults observer by solving a Lyapunov equation. The simulation results demonstrate the robust stability and satisfactory FTC performance of the proposed design approach.
22 Oct 2012
TL;DR: In this paper, an eigenstructure assignment fault detection approach to linear time invariant (LTI) systems is extended to Linear Parameter Varying (LPV) systems.
Abstract: In this paper, an eigenstructure assignment fault detection approach to linear time invariant (LTI) systems is extended to Linear Parameter Varying (LPV) systems. Fault detection filter design algorithms using eigenstructure assignment have been widely studied for LTI systems. However, LPV strategies are very useful for systems which have no unique equilibrium and are difficult to linearize. The parametric eigenstructure assignment approach is used to design an observer as a residual generator by viewing the varying parameters as fixed parameters in the design procedure. The residual observer feedback structure is implemented using a measured scheduling parameter An example is given of actuator fault detection of a two-link manipulator system.
22 Oct 2012
TL;DR: In this paper, phase plane description and modulation of the performance for a nonlinear UAV system based on variable structure control (VSC) by reaching sliding mode is discussed, where phase analysis approach is applied to achieve a robust controller for a complex nonlinear system.
Abstract: This paper concerns phase plane description and modulation of the performance for a nonlinear Unmanned Aerial Vehicle (UAV) system based on Variable Structure Control (VSC) by reaching sliding mode. The novelty lies in the application of a phase analysis approach to achieve a robust controller for a complex nonlinear system. The aircraft dynamics are introduced and approximately linearized and decoupled on-line using feedback linearization theory. Then the sliding mode control (SMC) scheme is accomplished for the decoupled sub-channels. The phase modulation method is applied for theoretically ensuring further robustness. The simulation results demonstrate the efficiency and effectiveness of the proposed strategy.
TL;DR: In this paper, the authors proposed an active fault tolerant control (FTC) scheme for a nonlinear aircraft system with different faults acting on three actuators and with wind turbulence affecting the vertical force.
TL;DR: In this paper, an approach using free parameterised observer gains, on a high fidelity nonlinear aircraft model from AIRBUS, is proposed to estimate the various fault scenarios occurring for different flight conditions, aiming to maximize the robustness of the reference-actual residual error signal to nonlinear uncertainty, disturbances, faults and system inputs.
22 Oct 2012
TL;DR: In this article, the assignment of a desired eigenstructure to linear parameter-varying (LPV) systems is considered as an extended version of the corresponding eigen-structure assignment problem for linear time-invariant systems.
Abstract: This paper is concerned with the assignment of a desired eigenstructure to linear parameter-varying (LPV) systems as an extended version of the corresponding eigenstructure assignment problem for linear time-invariant systems. Based on a complete parametric solution of parametric generalized Sylvester matrix equation, a controller design method is proposed to guarantee a low sensitivity of the closed-loop eigenvalues. The observer state feedback structure is considered for output feedback control design. An example of control for a satellite attitude system is used to demonstrate the usefulness of the proposed approach.
22 Oct 2012
TL;DR: In this article, the authors propose a new strategy for robust decentralized control in which each subsystem uses an observer-based state estimate structure invoking an approach to separation principle recovery, based on Integral Sliding Model Control (ISMC), with careful consideration of both matched and unmatched uncertainties arising from interconnections and disturbances.
Abstract: The problem of robust decentralization of uncertain inter-connected systems is concerned with the goal of de-coupling a Lipschitz non-linear systems into individual “decentralized” subsystems satisfying security and fault-tolerance objectives. This work proposes a new strategy for robust decentralized control in which each subsystem uses an observer-based state estimate structure invoking an approach to separation principle recovery, based on Integral Sliding Model Control (ISMC) with careful consideration of both matched and unmatched uncertainties arising from inter-connections and disturbances. The proposed design strategy for the linear observer and uncertainty de-coupling designs involves a single LMI. An example of 3 unstable inter-connected non-linear systems is used to illustrate the power of the approach.
22 Oct 2012
TL;DR: In this paper, a systematic adaptive sliding mode controller design for the decentralized system with nonlinear interactions and unmatched uncertainties is proposed, which obviates the use of regular transformation, by solving a simple LMI-based optimization problem.
Abstract: This paper proposes a systematic adaptive sliding mode controller design for the decentralized system with nonlinear interactions and unmatched uncertainties. An adaptive tuning approach is developed to deal with unknown but bounded uncertainties/interactions. The sliding surface is designed which obviates the use of regular transformation, by solving a simple LMI-based optimization problem. The feasibility of the LMIs is also discussed in this paper. Finally, a numerical example is used to illustrate this method.
TL;DR: It is shown that matched disturbances and interactions can be rejected using an adaptive form of sliding mode control, whilst the unmatched interactions are attenuated by H ∞ control.
TL;DR: In this paper, the authors proposed a fault-tolerant tracking strategy based on a sensor fault hiding approach through the design of an estimator as an intermediate stage of redundancy acting between the system outputs and the controller inputs such that the controller always receives a fault free signal.