Active Fault Tolerant Control Approach Research Articles

Cascade sliding mode control implementation in photovoltaic power supply for camping-car applications

A cascade proportional integral sliding mode control for a two-stage interleaved boost converter (2IBC) serving as a reliable supplementary power source for camping-car applications is reported. Unlike the active fault-tolerant control approaches used for interleaved boost converters, which require controller reconfiguration, the proposed control scheme is passive fault-tolerant and does not require reconfiguration in the event of a faulty stage. The 2IBC model is analyzed together with the most important parasitic parameters, then, the averaged state-space model is derived to implement the control scheme. The appropriate linear cascade control is determined by using the small-signal equivalent model and improving the robustness and dynamic performance, thereby a proportional integrator controller is replaced by a sliding mode controller. The prototype system uses a signal processor and a low-power solar panel. The control code is generated by a PSIM software and loaded to the via a code composer tool. The experimental results validate the control design and demonstrate the efficiency of the proposed control scheme. In addition, the proposed controller ensures the continuity of service in the event of a faulty stage by verifying the reliability of the power supply.

An Integrated Design Approach for Fault-Tolerant Control of Switched LPV Systems With Actuator Faults

In this article, the active fault-tolerant control (FTC) issue is addressed for switched linear parameter varying (LPV) systems in the discrete-time domain. A general dwell-time property is considered in the system setup to govern the switching dynamics between subsystems, and the parameter variations within each subsystem are subjected to the polytopic uncertainties. The main innovation of the developed active FTC approach is to effectively cope with switched LPV models where both input and output matrices can be of parameter-dependent form. By virtue of a novel Lyapunov function approach depending on both dwell time and parameter variations, the joint task for fault detection, estimation, and compensation is fulfilled via an integrated design scheme. The input-to-state stability (ISS) conditions are obtained for the augmented faulty system satisfying a given ISS-gain performance requirement. The desired effect of active FTC is achieved in three critical steps: 1) construct a fault detection filter in terms of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {H}_{\infty }$ </tex-math></inline-formula> norm; 2) design an observer-based estimator to estimate the system states and faults simultaneously; and 3) synthesize a fault-tolerant controller with the LPV structure using the estimated states and faults for fault compensation. Finally, an application example is utilized to illustrate the efficiency and availability of the proposed control approach.

Fault Diagnosis and Fault Tolerant Control of Wind Turbines: An Overview

Wind turbines are playing an increasingly important role in renewable power generation. Their complex and large-scale structure, however, and operation in remote locations with harsh environmental conditions and highly variable stochastic loads make fault occurrence inevitable. Early detection and location of faults are vital for maintaining a high degree of availability and reducing maintenance costs. Hence, the deployment of algorithms capable of continuously monitoring and diagnosing potential faults and mitigating their effects before they evolve into failures is crucial. Fault diagnosis and fault tolerant control designs have been the subject of intensive research in the past decades. Significant progress has been made and several methods and control algorithms have been proposed in the literature. This paper provides an overview of the most recent fault diagnosis and fault tolerant control techniques for wind turbines. Following a brief discussion of the typical faults, the most commonly used model-based, data-driven and signal-based approaches are discussed. Passive and active fault tolerant control approaches are also highlighted and relevant publications are discussed. Future development tendencies in fault diagnosis and fault tolerant control of wind turbines are also briefly stated. The paper is written in a tutorial manner to provide a comprehensive overview of this research topic.

Integrated FDI/FTC approach for wind turbines using a LPV interval predictor subspace approach and virtual sensors/actuators

In order to keep wind turbines connected and in operation at all times despite the occurrence of some faults, advanced fault detection and accommodation schemes are required. To achieve this goal, this paper proposes to use the Linear Parameter Varying approach to design an Active Fault Tolerant Control for wind turbines. This Active Fault Tolerant Control is integrated with a Fault Detection and Isolation approach. Fault detection is based on a Linear Parameter Varying interval predictor approach while fault isolation is based on analysing the residual fault signatures. To include fault-tolerance in the control system (already available in the considered wind turbine case study based on the well known SAFEPROCESS benchmark), the information of the Fault Detection and Isolation approach block is exploited and it is used in the implementation of a virtual actuator and sensor scheme. The proposed Active Fault Tolerant Control is evaluated using fault scenarios which are proposed in the wind turbine benchmark to assess its performance. Results show the effectiveness of the proposed Active Fault Tolerant Control approach in faulty situation.

An active fault-tolerant control method based on moving window hidden Markov model

This article proposes a new active fault-tolerant control (AFTC) method based on moving window hidden Markov models (MWHMM) for nonlinear processes. The AFTC approach could be divided into two steps, fault detection and identification (FDI) and fault accommodation. The information obtained from the FDI step is used for fault accommodation, under the framework of model predictive control (MPC). Firstly, MWHMM is utilized for online fault detection and identification. Moreover, to improve the discernibility of the prediction status probability density function (PDF) for identification between the normal and faulty modes, the Hellinger distance, which could measure the similarity between probability distributions, is introduced. As the separability between the normal and faulty modes is increased, the accuracy and reliability of fault identification by MWHMM is greatly improved. At last, not only the occurrence of a single fault but also the occurrence of a hybrid fault, which means that multiple faults occur simultaneously, is considered in this article. The validity of the suggested method is verified by the simulation results on a three-tank water system.

Sensor Fault Tolerant Control for Aircraft Engines Using Sliding Mode Observer

This paper investigated the problem of fault estimation and fault-tolerant control (FTC) against sensor faults for aircraft engines. By applying a second order sliding mode observer (SOSMO) to the engine on-board model, estimations of the system states and sensor faults could be obtained simultaneously, and the result of state estimation was unaffected when using the reduced-order sliding mode system. This result gave rise to the idea to use the estimated states instead of physical sensor signal in the engine close-loop feedback control. Unlike those using passive FTC concepts, the tradeoff between control performance and robustness was inherently unnecessary. Meanwhile, compared to active FTC approaches, because any classical state/output feedback method can be directly applied to the proposed scheme without any controller reconfiguration, extra undesired dynamic responses caused by parameter reconfiguring were avoided. In this paper, the proposed FTC scheme was tested on the nonlinear model of a civil aircraft turbofan engine, and numerical simulation results showed satisfactory sensor FTC performance.

Active fault-tolerant control approach design for rigid spacecraft with multiple actuator faults

In this study, the active fault-tolerant control problem is investigated for a rigid spacecraft in the presence of inertia uncertainty, external disturbance, multiple actuator faults and actuator saturation. The attitude system model of spacecraft and actuator fault model are first given. A sliding mode–based fault detection observer and a radial basis function neural networks–based fault estimation observer are designed to detect the time of actuator fault occurred and estimate the amplitude of unknown fault, respectively. On that basis, an active fault-tolerant control scheme is proposed to accommodate the effects of multiple actuator faults, and it guarantees that the state trajectory of attitude systems without actuator saturation converges to a neighborhood of the origin in finite time. Another active fault-tolerant control scheme is further proposed in actuator saturation constraint case; it ensures that all the closed-loop signals are finite time convergence. Finally, simulation results are given to illustrate the effectiveness of the proposed fault-tolerant control approach.

Active fault tolerant control based on a neuro fuzzy inference system applied to a two shafts gas turbine

ABSTRACTThe main aim of the present work is development of an active fault tolerant control for two shafts gas turbine fault detection and isolation based on a neuro fuzzy inference system adaptive approach. This approach combines the advantages of the neural networks with the fuzzy inference systems. The reconfiguration mechanism of the proposed active fault tolerant control is performed by detecting the malfunction of the studied gas turbine in an automatic manner. The obtained experimental results are presented to illustrate the great interest of the developed active fault tolerant control approach and to demonstrate its effectiveness in maintaining the stability with acceptable performance under the presence of defects in the presented gas turbine.

Active Fault Tolerant Control Based on a Novel Tracking Differentiator for Elevating Stage Control System

In view of the speed sensor faults in elevating stage control system, an active fault tolerant control approach based on a novel tracking differentiator is proposed in this paper. First, the analytical redundancy relationship between the velocity and displacement signals in a dual closed loop control system is used to detect a fault. When the deviation between the differential of normal displacement sensor signal and the fault speed sensor output exceeds a certain threshold value, a fault can be considered to occur. Secondly, after a fault is detected, the output of the fault sensor is replaced immediately with the differential signal of the output from a normal sensor to ensure the safety of the postfault system. In the process of signal differential, considering the drawbacks of the traditional method which uses inertial element to approximate differentiator and complex parameter tuning of Han’s Tracking Differentiator (TD), a novel tracking differentiator based on hyperbolic tangent function (Tanh-TD) is designed. Thirdly, in order to avoid the switching vibration and improve the reliability of FDD, a continuous smooth switching tactic based on exponential function is constructed. The simulation results show that the fault diagnosis method is simple and timely, the designed tracking differentiator is fast and effective, and the effect of the fault tolerant control based on smooth switching strategy is also satisfactory.

A finite frequency domain-based approach for active fault tolerant control of linear time-delay systems with residual feedback

This paper presents a finite frequency-based active fault tolerant control approach for the compensation of unknown failures in linear time-delay plants. An integration of fault detection filter based on observer technology and [Formula: see text] controller in residual feedback form is considered in the active fault tolerant control system. Different from the traditional schemes, exact fault estimation is not necessary in the proposed active fault tolerant control. To achieve the desired system performance when a fault occurs, the residual is directly embedded in the control loop as a feedback term to compensate the influence of fault. By employing the Generalized Kalman–Yakubovich–Popov lemma, we derive the sufficient conditions of the existence of such an active fault tolerant control plant, and iterative algorithms are applied to obtain the solutions to the fault detection filter and controller parameter matrices. Finally, simulation results are proposed to demonstrate the effectiveness of the developed scheme.

An active fault tolerant control approach to an offshore wind turbine model

The paper proposes an observer based active fault tolerant control (AFTC) approach to a non-linear large rotor wind turbine benchmark model. A sensor fault hiding and actuator fault compensation strategy is adopted in the design. The adapted observer based AFTC system retains the well-accepted industrial controller as the baseline controller, while an extended state observer (ESO) is designed to provide estimates of system states and fault signals within a linear parameter varying (LPV) descriptor system context using linear matrix inequality (LMI). In the design, pole-placement is used as a time-domain performance specification while H∞ optimization is used to improve the closed-loop system robustness to exogenous disturbances or modelling uncertainty. Simulation results show that the proposed scheme can easily be viewed as an extension of currently used control technology, with the AFTC proving clear “added value” as a fault tolerant system, to enhance the sustainability of the wind turbine in the offshore environment.

Trajectory planning/re-planning for satellite systems in rendezvous mission in the presence of actuator faults based on attainable efforts analysis

The objective of fault-tolerant control (FTC) is to minimise the effect of faults on system performance (stability, trajectory tracking, etc.). However, the majority of the existing FTC methods continue to force the system to follow the pre-fault trajectories without considering the reduction in available control resources caused by actuator faults. Forcing the system to follow the same trajectories as before fault occurrence may result in actuator saturation and system's instability. Thus, pre-fault objectives should be redefined in function of the remaining resources to avoid potential saturation. The main contribution of this paper is a flatness-based trajectory planning/re-planning method that can be combined with any active FTC approach. The work considers the case of over-actuated systems where a new idea is proposed to evaluate the severity of faults occurred. In addition, the trajectory planning/re-planning approach is formulated as an optimisation problem based on the analysis of attainable efforts domain in fault-free and fault cases. The proposed approach is applied to two satellite systems in rendezvous mission.

Fault tolerant nonlinear control with applications to an automated transit bus

This paper presents an integrated structure for a passive and active fault tolerant control (FTC) design approach in the framework of a robust nonlinear control technique called Dynamic Surface Control (DSC). As motivated by the automated vehicle application, we consider two categories of possible faults: pre-specified (a priori) and non-specified faults. It is first shown that DSC can be considered as a passive FTC approach in the sense that it gives simultaneous robust stability to a set of nonlinear systems even in the presence of model uncertainties and the pre-specified faults. Then, the non-specified fault is classified depending on the fault’s impact on the closed-loop system and isolatability from a fault detection and diagnosis (FDD) system. If a fault is both intolerable and isolatable, an active FTC approach is taken which includes FDD and controller reconfiguration. More specifically, trajectory reconfiguration is considered to accommodate the actuator fault, i.e., to compensate for the performance loss due to the fault within the framework of a switched hierarchical structure. Finally, the integrated structure for the longitudinal control of an automated transit bus is designed through the proposed method. Simulation results of the fault tolerant controller are shown for both single and multiple multiplicative faults. This controller was implemented on the California PATH transit buses in a demonstration of automated public transportation technology in San Diego, California in August of 2003.

A multiple model based approach for fault tolerant control in non-linear systems

A new fault tolerant control (FTC) system devoted to non linear stochastic system described by multiple linear models is proposed in this paper. The proposed active FTC approach is composed of three stages: nominal controller, fault detection and isolation (FDI) scheme that is based on a bank of robust fault decoupling Kalman filters and a reconfiguration mechanism. Fault free residuals generated by a bank of Kalman Filter are used first to select the most appropriate model to characterize dynamic behavior of the system. Then, evaluation of the fault sensitive residuals provides information about the location and time occurrence of the faults. Once a fault has been detected and isolated, residuals are monitored to activate a fault compensation loop in order to cancel the fault effect on to the state vector. The effectiveness and performances of the method are validated in simulation considering a classical non linear benchmark.