Fault-tolerant Control System Design Research Articles

Passive Fault Tolerant Control System Using Feed-forward Neural Network for Two-Tank Interacting Conical Level Control System Against Partial Actuator Failures and Disturbances

Abstract A novel approach for passive fault-tolerant control (PFTC) system design against actuator faults is proposed. The scheme is based on Feed-forward Neural Network (FFNN) plus conventional PI controller, during the fault occurred into system FFNN will give additional control output to the system according to fault magnitude. The FFNN will trained using back-propagation algorithm. To eliminate the steady-state tracking error, the PI controller is also incorporated. The following fault type and input signals are considered: abrupt, step, sine, and trapezoidal trajectory inputs. The effectiveness and the superiority of the proposed approach are demonstrated using Two-Tank Interacting Conical Level Control System (TTICLCS) example. The simulation performed in MATLAB Simulink platform, also different integral errors like IAE, ISE and IATE are presented to validate the proposed approach.

Design of an actuator fault-tolerant controller for an air vehicle with nonlinear dynamics

In this paper, a novel method is presented to design an autopilot for an air vehicle with a polynomial nonlinear model. This method employs the nonlinear model directly in the control design process without the need for local linearization about an operating point. It is shown that the control design problem can be formulated as a sum-of-squares optimization problem. This method guarantees exponential stability of the closed-loop nonlinear system by introducing a polynomial Lyapunov function. The nonlinear dynamic model of air vehicles can usually be represented in the polynomial form. Therefore, the proposed method can widely be applied to design an air vehicle autopilot. Besides using the proposed method along with the projection based and online redesign methods, a fault-tolerant controller is designed for the air vehicle. Furthermore, a new approach is developed by combination of these methods to fault-tolerant control system design. The proposed method is applied to design a fault-tolerant controller for a nonlinear pitch-axis model of an air vehicle subject to loss of effectiveness actuator fault. The simulation results show the efficiency of the proposed method.

Resilience and risk analysis of fault-tolerant process control design in continuous pharmaceutical manufacturing

The shift from batch to continuous manufacturing, which is occurring in the pharmaceutical manufacturing industry has implications on process safety and product quality. It is now understood that fault-tolerant process control of critical process parameters (CPPs) and critical quality attributes (CQAs) is of paramount importance to the realization of safe operations and quality products. In this study, a systematic framework for fault-tolerant process control system design, analysis, and evaluation of pharmaceutical continuous oral solid dosage manufacturing is proposed. The framework encompasses system identification, controller design and analysis (controllability, stability, resilience, etc.), hierarchical three-level control structures (model predictive control, state estimation, data reconciliation, etc.), risk mapping, assessment and planning (Risk MAP) strategies, and control performance evaluation. The key idea of the proposed framework is to identify the potential risks associated with the control system design itself, the material property variations, and other process uncertainties, under which the control strategies must be evaluated. The framework is applied to a continuous direct compaction process, specifically the feeding-blending subsystem, wherein the major source of variance in the process operation and product quality arises. It is demonstrated, using simulations and experimentally, that the process operation failures and product quality variations in the feeding-blending system can be mitigated and managed through the proposed systematic fault-tolerant process control system design and risk analysis framework.

The method providing fault-tolerance for information and control systems of the industrial mechatronic objects

The paper deals with the provision of information and control system fault-tolerance. Nowadays, a huge quantity of industrial mechatronic objects operate within hazardous environments, where the human is not supposed to be. So the question of fault-tolerant information and control system design and development becomes the cornerstone of a large amount of industrial mechatronic objects. Within this paper, a new complex method of providing the reconfigurable systems fault-tolerance is represented. It bases on performance redundancy and decentralized dispatching principles. The key term within the method presented is a ‘configuration’, so the model of the configuration forming problem is represented too, and simulation results are given and discussed briefly.

A polytopic LPV approach to active fault tolerant control system design for three-phase induction motors

ABSTRACTThis paper presents a new active approach in order to design a model-based fault-tolerant control (FTC) system for three-phase induction motors (IMs) subjected to mechanical faults caused by stator and rotor failures. In this approach, a nominal controller achieves control objectives in fault-free case. The main part of this approach is related to design a fault/state observer for simultaneous estimation of additive faults which model the mechanical faults and axial fluxes in any operating conditions. For trade-off between robustness and performance in the presence of uncertainties and faults, this fault/state observer design problem is reduced to a well-known mixed optimisation problem by using polytopic linear parameter-varying approach. The FTC system consists of a nominal controller together with an observer which provides auxiliary inputs using the estimation of additive faults in order to compensate their undesirable effects on IM performance. The simulation results are shown to illustrate the effectiveness of the proposed approach to compensate the mechanical faults in IM.

INTEGRATION FAULT DETECTION AND TOLERANT CONTROL IN MICRO-SATELLITE ATTITUDE PROPULSION MODE APPLICATION

The paper refers to a tolerant control method which is reconfigurable to micro-satellites when they are out of order. The integrated approach to the design of thruster control reconfigurable fault-tolerant control system is proposed. The scheme includes a control effectiveness factor and a reconfigurable fault-tolerant controller. The fault detection, diagnosis and controller reconfiguration are carried out using the control effectiveness factor based on the information from a two-stage Kalman filter. By using the two-stage Kalman filter and digital controller, the nonlinear plant will be discretized. We present sufficient conditions under which a discrete-time controller that input-to-state stabilizes an approximate discrete-time model of a nonlinear plant with disturbances. The result shows the method enables us to solve the system faults and meet the requirement when there is a fault in the micro-satellites attitude control system.

Robust FDI for fault-tolerant thrust allocation with application to spacecraft rendezvous

This paper deals with the design and validation of an active fault-tolerant control system to detect, isolate and accommodate a single thruster fault affecting the thruster-based propulsion system of an autonomous spacecraft. The proposed method consists of a fault detector for robust and quick fault detection, a two-stage hierarchical isolation strategy for fault isolation, and an online control allocation unit scheduled by the isolation scheme for fault tolerance. A new factorization approach for the uncertain inertia matrix inverse is proposed. Thanks to this factorization, a novel robust Nonlinear Unknown Input Observers (NUIO) approach is proposed based on LMIs which ensure maximization of the admissible Lipschitz constant while at the same time satisfying an L2 gain bound and some constraints on the observer dynamics. At the first stage of the isolation scheme, a bank of NUIOs is used to identify a subset of possible faulty thrusters. Then, at the second stage, an EKF is introduced to estimate the torque bias directions. Using these directions, jointly with the detector׳s residual and the information obtained from the first stage, a set of explicit rules is derived to unambiguously isolate the faulty thruster. A Monte Carlo campaign, based on a simulator developed by Thales Alenia Space industries, is conducted in the context of a terminal rendezvous phase of the Mars Sample Return mission. Mission oriented criteria demonstrate that the proposed strategy is able to cope with a large class of realistic thruster faults and to achieve mission success.

Adaptive Observer-Based Fault-Tolerant Control Design for Uncertain Systems

This study focuses on the design of the robust fault-tolerant control (FTC) system based on adaptive observer for uncertain linear time invariant (LTI) systems. In order to improve robustness, rapidity, and accuracy of traditional fault estimation algorithm, an adaptive fault estimation algorithm (AFEA) using an augmented observer is presented. By utilizing a new fault estimator model, an improved AFEA based on linear matrix inequality (LMI) technique is proposed to increase the performance. Furthermore, an observer-based state feedback fault-tolerant control strategy is designed, which guarantees the stability and performance of the faulty system. Moreover, the adaptive observer and the fault-tolerant controller are designed separately, whose performance can be considered, respectively. Finally, simulation results of an aircraft application are presented to illustrate the effectiveness of the proposed design methods.

Real-Time Implementation of Fault-Tolerant Control Systems With Performance Optimization

In this paper, two online schemes for an integrated design of fault-tolerant control (FTC) systems with application to Tennessee Eastman (TE) benchmark are proposed. Based on the data-driven design of the proposed fault-tolerant architecture whose core is an observer/residual generator based realization of the Youla parameterization of all stabilization controllers, FTC is achieved by an adaptive residual generator for the online identification of the fault diagnosis relevant vectors, and an iterative optimization method for system performance enhancement. The performance and effectiveness of the proposed schemes are demonstrated through the TE benchmark model.

Recursive Actuator Fault Detection and Diagnosis for Emergency Landing of UASs

This paper presents a practical recursive fault detection and diagnosis (FDD) scheme for online identification of actuator faults for unmanned aerial systems (UASs) based on the unscented Kalman filtering (UKF) method. The proposed FDD algorithm aims to monitor health status of actuators and provide indication of actuator faults with reliability, offering necessary information for the design of fault-tolerant flight control systems to compensate for side-effects and improve fail-safe capability when actuator faults occur. The fault detection is conducted by designing separate UKFs to detect aileron and elevator faults using a nonlinear six degree-of-freedom (DOF) UAS model. The fault diagnosis is achieved by isolating true faults by using the Bayesian Classifier (BC) method together with a decision criterion to avoid false alarms. High-fidelity simulations with and without measurement noise are conducted with practical constraints considered for typical actuator fault scenarios, and the proposed FDD exhibits consistent effectiveness in identifying occurrence of actuator faults, verifying its suitability for integration into the design of fault-tolerant flight control systems for emergency landing of UASs.

Nonlinear Actuator Fault Detection for Small-Scale UASs

This paper presents a recursive strategy for online detection of actuator faults on a unmanned aerial system (UAS) subjected to accidental actuator faults. The proposed detection algorithm aims to provide a UAS with the capability of identifying and determining characteristics of actuator faults, offering necessary flight information for the design of fault-tolerant mechanism to compensate for the resultant side-effect when faults occur. The proposed fault detection strategy consists of a bank of unscented Kalman filters (UKFs) with each one detecting a specific type of actuator faults and estimating corresponding velocity and attitude information. Performance of the proposed method is evaluated using a typical nonlinear UAS model and it is demonstrated in simulations that our method is able to detect representative faults with a sufficient accuracy and acceptable time delay, and can be applied to the design of fault-tolerant flight control systems of UASs.

Fault tolerant control system design by using clustering algorithms of data mining

Fault tolerant control system design by using clustering algorithms of data mining

Fault-tolerant control systems: A comparative study between active and passive approaches

This paper demystifies active and passive fault-tolerant control systems (FTCSs) by examining the similarities and differences between these two approaches from both philosophical and practical points of view. Even though the control objectives of both approaches are the same, each method uses its own unique ways to achieve the objectives. Therefore, different approaches can lead to seemingly different results. Advantages and limitations of each method are examined through at philosophical level as well as quantitative case studies using an aircraft flight control system as a test system. A distinctive feature of this paper is that it provides an objective assessment of the two most popular fault-tolerant control system design methodologies in an unbiased and comparative setting.

LPV design of fault-tolerant control for road vehicles

LPV design of fault-tolerant control for road vehiclesThe aim of the paper is to present a supervisory decentralized architecture for the design and development of reconfigurable and fault-tolerant control systems in road vehicles. The performance specifications are guaranteed by local controllers, while the coordination of these components is provided by a supervisor. Since the monitoring components and FDI filters provide the supervisor with information about the various vehicle maneuvers and the different fault operations, it is able to make decisions about necessary interventions into the vehicle motions and guarantee reconfigurable and fault-tolerant operation of the vehicle. The design of the proposed reconfigurable and fault-tolerant control is based on an LPV method that uses monitored scheduling variables during the operation of the vehicle.

Fault-tolerant Compensation Control Incorporating Actuator Criticality

In this paper, actuator criticality analysis is integrated in the design of active fault-tolerant control systems. The main objective consists in the fault-tolerant controller synthesis which guarantees a highest overall system reliability while still maintaining immediate stability and tracking performance of reconfigured system. To achieve this task, an actuator criticality indicator is defined and incorporated in the fault-tolerant controller design. Such metric is implemented to manage the control inputs in order to improve the system dependability both in normal operation and in the presence of faults. Actuator criticality analysis of systems modeled by a state space representation is proposed. A design of the fault-tolerant compensation controller is reformulated as a linear matrix inequality problem.

Fault-Tolerant Flight Control System Design Against Control Surface Impairments

An active fault-tolerant flight control system design technique against control surface impairments is proposed here. The aircraft control surface impairments are modeled as a polytopic linear parameter varying (LPV) system. Relying on the existing control surface redundancy of the aircraft, both state feedback and static output feedback controllers are synthesized against various degrees of control surface impairments. Simulation examples of an aircraft subject to inner elevon impairments have been used to illustrate the design process and to demonstrate the effectiveness of the proposed method.

A survey of fault-tolerant networked control system design

This paper gives a survey on recent reserch activities and published results in the area of fault detection and fault-tolerant control in networked control systems.

ℒ︁2 gain analysis of linear systems with a single switching

AbstractFor analysis and design of fault‐tolerant control systems, it is very important to evaluate the effects of failures, especially the transient responses caused by failures. This paper considers the ℒ︁2 gain analysis of linear systems with a single switching, and gives necessary and sufficient conditions for the analysis. Also, the worst disturbance corresponding to the switching ℒ︁2 gain is explicitly characterized. Copyright © 2010 John Wiley & Sons, Ltd.

Fault tolerant flight control system design using a multiple model adaptive controller

This article presents a fault tolerant flight control system using multiple model adaptive control (MMAC). To apply this method to the aircraft, model reference adaptive control is extended to a linear discrete-time multiple-input multiple-output system. Multiple models can be determined by various flight conditions with respect to possible aircraft fault situations. In this article, the damages of control effectors are considered as aircraft faults. The aerodynamic coefficients of fault model are derived by a damaged control surface area. In the MMAC, how to select a proper fault model and how to switch into the selected model are significant issues. The conventional mode switching method, however, has a tendency to make the system fluctuate because of frequent mode switching, and therefore may deteriorate the performance of the aircraft. In this study, the modified adaptive mode switching scheme and new decision logic are proposed to improve the adaptiveness in the transient state dynamics of system. Numerical simulations are performed for a linear discrete-time aircraft model to validate the effectiveness of the proposed method.

Application of agent technology concepts to the design of a fault-tolerant control system

This work concerns the applicability of agent technology concepts to the design of a plant fault-tolerant control system. The operation of the fault-tolerant system is enhanced by decomposing it into autonomous subsystems and by turning them into agents. The detailed development of one of the agents, the feed line of the process, is presented and its performance is tested by simulation. The proposed framework meets the control objectives and features a significant level of fault tolerance to sensor and actuator failures. This is achieved using an observer based fault detection and diagnosis (FDD) unit. Moreover, this work shows how the control strategy may be altered to tackle a case of severely impacted control capability.