A reverse osmosis laboratory plant for experimenting with fault-tolerant control

The Flight Control System (FCS) is considered as the brain of an aerial vehicle. It is a mechanism through which pilot’s commands are transferred to the actuators of the aircraft control surfaces. In order to ensure safety and increase reliability of aerial vehicles, development of fault tolerant FCSs has been the focus of research community for past few decades. Fault tolerant ability enables an aircraft to maintain satisfactory performance even in the state of a fault. Fault Tolerant Control Systems (FTCS) are categorized as passive and active control systems. Passive FTCS are designed to mitigate the effects of certain known faults. These faults can be related to sensor failure, actuator failure, or system component failure. On the other hand, active FTCS contain a controller reconfiguration mechanism, whereby, they can adjust the controller input online to mitigate the effects of the faults. In this way, they can accommodate complicated and versatile faults as compared to their passive counterparts. This paper presents a review of significant research during last decade in active fault tolerant control with applications to FCSs. A review of state-of-the-art works in this domain has also been presented. Upon review, these state-of-the-art research interests have been categorized into respective categories. Furthermore, research works have been cataloged based on their technology readiness levels. Based on these reviews, future research directions have also been highlighted.

Industry demand high reliability in their system especially in a hazardous working environment. This work proposed a computer-based Fault Tolerant Control (FTC) system under simultaneous actuator and sensor faults of a flexible robot manipulator system under the event of loss effectiveness on more than one component can be a critical fault scenario in industrial system. This proposed method is simulated using a Matlab/Simulink software that interface with a data acquisition (DAQ) NI-PCI6221 board using an ISA bus data communication. In this approach, the FTC system has an adaptive feature where it able to accommodate the faults automatically using an adaptive proportional-integral-derivative (APID) controller. Unlike the conventional PID controller, all the proposed APID control parameters, namely, , , and are adjusted online through online adaptation laws even under variation of fault scenarios. The proposed APID controller is shown to provide an accurate positioning control with faster response even under the variation of types of faults using the computer-based measurement in DAQ system and control systems that is designed based on the real-time Matlab/Simulink toolbox as compared to the conventional PID controller. Industry demand high reliability in their system especially in a hazardous working environment. This work proposed a computer-based Fault Tolerant Control (FTC) system under simultaneous actuator and sensor faults of a flexible robot manipulator system under the event of loss effectiveness on more than one component can be a critical fault scenario in industrial system. This proposed method is simulated using a Matlab/Simulink software that interface with a data acquisition (DAQ) NI-PCI6221 board using an ISA bus data communication. In this approach, the FTC system has an adaptive feature where it able to accommodate the faults automatically using an adaptive proportional-integral-derivative (APID) controller. Unlike the conventional PID controller, all the proposed APID control parameters, namely, , , and are adjusted online through online adaptation laws even under variation of fault scenarios. The proposed APID controller is shown to provide an accurate positioning control with faster response even under the variation of types of faults using the computer-based measurement in DAQ system and control systems that is designed based on the real-time Matlab/Simulink toolbox as compared to the conventional PID controller.

This paper presents an integrated Fault-Tolerant Control (FTC) system with a Fault Detection and Isolation (FDI) scheme for the total control surface failures of a commercial aircraft. Since a Propulsion Controlled Aircraft (PCA) is a very challenging task, little attention has been paid to the analysis and design of the overall system including both a FDI scheme and a FTC system. We propose an overall Fault-Tolerant Flight Control (FTFC) system for the back up of the full loss of hydraulic systems. The reconfigurable controller with Simple Adaptive Control (SAC) is automatically tuned and switched based on the fault parameters estimated by a FDI scheme. This method also enables us to ensure the nominal flight performance in fault free situations. In this study, after the full loss of elevator control occurs on the aircraft, the pitch angle can be controlled by the engine thrust input instead of the elevator input.

In the field of UUV control system design, fault-tolerant control and redundancy management is the important method to improve system reliability. This paper addresses a fault-tolerant steering control system to improve the reliability of UUV. A novel fault-tolerant control system, which uses the hybrid redundant structural configuration based on the characteristics of the X rudder UUV, is designed. The configuration is based on duplex redundant control calculation coupled with a quadruplex redundant actuator. Redundancy management strategies and algorithms are used to implement the UUV fault-tolerant control. The analysis indicates that the reliability of the control system which used the proposed configuration is improved obviously compared with the conventional configuration.

In this paper, we investigate the problem of fault tolerant controller (FTC) design for systems affected by actuator failures. For this purpose, we compare the performance of the closed-loop systems obtained from designing three different controllers: one is the traditional H 1 controller designed to work in the healthy condition, the second one is a robust LPV controller that is scheduled based upon an estimate of the fault signals, and finally a robust H 1 controller that takes into account the uncertainty parameters representing the fault signals. The design approaches presented in this paper are validated on a Highly Maneuverable Aircraft Technology (HiMAT) vehicle model subject to the loss of control effectiveness. I. Introduction Fault Tolerant Control Systems (FTCS) are a class of highly sophisticated control functions designed in a unified framework in order to maintain high levels of system integrity, performance and redundancy. Two classes of FTCS are defined in the literature: passive and active designs. A passive FTCS can tolerate faulty operation while maintaining satisfactory performance without any control reconfiguration. An active FTCS (AFTCS), on the other hand, needs a fault detection and isolation (FDI) scheme and a control reconfiguration mechanism. The key-role for the FDI scheme is to continuously monitor the system behavior to detect faulty operation and locate failed components. The decisions made by the FDI scheme command a reconfiguration mechanism to reconfigure (or sometimes restructure) the control law in real-time basis accordingly. A bibliographical review on the definition and classes of FTCS, major components of FTCS, and review of some of the design methodologies can be found in the survey papers. 8, 11 Since an FDI module and an FTC law are individually designed ignoring the other dynamics, it is required to analyze the whole FTC system including both FTC law and the FDI module before they are implemented in the actual system. A typical method for analyzing the FTC system is full nonlinear simulation with the known command inputs for the possible fault scenarios. After detailed simulations, the FTC system may be validated for the possible fault scenarios with expensive computational costs. Generally, an active FTC law is designed based on an open-loop system modeled as a function of fault parameters under the assumption that the parameters are immediately identified by the FDI module. Recently, using linear matrix inequality (LMI) optimization-based solutions, active FTC laws have been synthesized in the linear parameter varying (LPV) framework, whose dynamics varies as the scheduling parameters change. Open-loop dynamics of a system affected by the actuator or sensor faults is modeled as an LPV system in which the scheduling parameters are fault parameters that represent fault occurrences at actuators or sensors or both. An FTC-LPV law, designed based on the open-loop system, can robustly stabilize the closed-loop system and achieve the desired level of performance during a fault occurrence under the assumption that fault parameters can be measured in real-time. There are only few work in the literature looking at the problem of FTC control design from an LPV framework perspective. 3, 5‐7, 9, 10 Kanev 6 presents two methods for active FTC-LPV design including a deterministic approach that can deal with multiplicative sensor and actuator faults, as well as, a probabilistic design method which makes it possible to consider, in addition to sensor and actuator faults, component faults in order to schedule the LPV controller on both the fault estimates and their uncertainty sizes. The deterministic approach designs off-line a bank of LPV controllers for specific fault scenarios. Then, based on the fault estimates, the controller that achieves the best performance is switched on. This LPV controller is subsequently scheduled by the size of the uncertainty in the fault estimate. The probabilistic-based design replaces the bank of controllers from the deterministic method by only a single LPV controller. The latter approach also considers (structured) model uncertainty in addition to the FDD uncertainty. Both approaches can be

Many applications of Reverse Osmosis (RO) desalination plants require fault tolerance, in particular when human life depends on the water purity. However, they have been little studied in the literature from this point of view, in particular, when small plants use a feed water bypass to modify the permeate conductivity by mixing a little amount of feed water with the permeate. Such plants have a different system configuration and different dynamic behavior from standard plants. The present work is a study on Fault-Tolerant Control (FTC) of a small plant with feed water bypass by using Model Predictive Control (MPC). Very satisfactory results show the advantages of using a fault-tolerant control system in this kind of plants.

This work deals with the modeling and design of fault tolerant traffic control systems for urban transportation networks. The dynamics of queue length in front of the intersections are captured by a nonlinear state space model where a limit-reset function is introduced to maintain the non-negativity of the queues for traffic conditions ranging from undersaturation to oversaturation. A fault-tolerant control system is then synthesized to maintains system integrity (stability and vehicle flow regulation) under partial system failure brought about by local faults such as sensor/actuator failure, vehicle accidents, severing of communication links, etc. It is shown that the fault-tolerant conditions are rather mild and can readily be satisfied by a properly designed decentralized PI-type controller. A detailed case study is also included in this work to demonstrate the properties of a fault tolerant traffic network.

Small satellites flying in formation present a more efficient and affordable way of achieving the same or better performance than a large satellite because of low cost, high density of functionality and a short development cycle. A key technology for achieving mission objectives is the attitude and orbit control system. The overall objective of this dissertation research focuses on developing advanced control strategies and fault tolerant control for satellite formation flying. It is necessary to design and operate the satellite formation flying system to reduce fuel consumption and improve control accuracy. This is a very challenging task due to the nonlinear nature of satellite formation dynamics and the risk of thrusters’ failures and sensors’ faults in the absence of hardware redundancy. A class of nonlinear leader-follower satellite formation flying systems subject to uncertain thrusters’ and sensors’ faults and external J2 disturbances has been studied applying fault detection and identification and second order sliding mode control methodologies. New fault detection and identification and fault tolerant control algorithms were compared with model based fault detection and identification and fault tolerant control algorithms in presence of large initial errors, timevarying external disturbances, and parameter uncertainties. The faults considered were modeled as constant or ramp faults. Numerical results demonstrated the effectiveness of the proposed active fault tolerant control under actuators’ and sensors’ faults. It has been shown that the proposed second order sliding mode control scheme can guarantee local asymptotic stability after system faults. Simulation results confirmed that the suggested control methodologies yield high formation keeping precision and effectiveness for leaderfollower formation flying systems. The tracking errors of the proposed second order sliding mode control, adaptive fuzzy sliding mode control, chattering free sliding mode control and classic sliding mode control resulting from the thruster faults are within 2 m, 4 m, 10 m and 1 m, respectively. The fuel consumption of the proposed second order sliding mode control was the least. It is also necessary to design a fault tolerant satellite attitude control system to reduce fuel consumption and improve control performance accuracy. The proposed fault tolerant attitude control algorithms were based on first order and higher order sliding mode control theory as well as fuzzy logic systems to achieve real time autonomous fault tolerant control. These algorithms were applied to attitude synchronization in both leader-follower formation flying and decentralized formation flying. Attitude synchronization during formation flying was examined considering actuator dynamics while decentralized attitude ynchronization was studied using graph theory with quaternion kinematics. The proposed fault tolerant control algorithm was compared with the existing satellite attitude system controllers in the literature and it was found that the proposed algorithm resulted in three axis attitude stabilization within 0.041◦ in all axes for the fault cases. The reaction wheels’ Coulomb friction, saturations, noise, dead-zones, bias fault and external disturbances are considered. Finally, a nonlinear adaptive fuzzy sliding mode controller was tested using embedded nanosatellite hardware on a frictionless spherical air bearing system. The test results showed attitude errors of 0.8◦ using the proposed controller while a proportional integral derivative controller resulted in 5◦ attitude errors.

Small satellites flying in formation present a more efficient and affordable way of achieving the same or better performance than a large satellite because of low cost, high density of functionality and a short development cycle. A key technology for achieving mission objectives is the attitude and orbit control system. The overall objective of this dissertation research focuses on developing advanced control strategies and fault tolerant control for satellite formation flying. It is necessary to design and operate the satellite formation flying system to reduce fuel consumption and improve control accuracy. This is a very challenging task due to the nonlinear nature of satellite formation dynamics and the risk of thrusters’ failures and sensors’ faults in the absence of hardware redundancy. A class of nonlinear leader-follower satellite formation flying systems subject to uncertain thrusters’ and sensors’ faults and external J2 disturbances has been studied applying fault detection and identification and second order sliding mode control methodologies. New fault detection and identification and fault tolerant control algorithms were compared with model based fault detection and identification and fault tolerant control algorithms in presence of large initial errors, timevarying external disturbances, and parameter uncertainties. The faults considered were modeled as constant or ramp faults. Numerical results demonstrated the effectiveness of the proposed active fault tolerant control under actuators’ and sensors’ faults. It has been shown that the proposed second order sliding mode control scheme can guarantee local asymptotic stability after system faults. Simulation results confirmed that the suggested control methodologies yield high formation keeping precision and effectiveness for leaderfollower formation flying systems. The tracking errors of the proposed second order sliding mode control, adaptive fuzzy sliding mode control, chattering free sliding mode control and classic sliding mode control resulting from the thruster faults are within 2 m, 4 m, 10 m and 1 m, respectively. The fuel consumption of the proposed second order sliding mode control was the least. It is also necessary to design a fault tolerant satellite attitude control system to reduce fuel consumption and improve control performance accuracy. The proposed fault tolerant attitude control algorithms were based on first order and higher order sliding mode control theory as well as fuzzy logic systems to achieve real time autonomous fault tolerant control. These algorithms were applied to attitude synchronization in both leader-follower formation flying and decentralized formation flying. Attitude synchronization during formation flying was examined considering actuator dynamics while decentralized attitude ynchronization was studied using graph theory with quaternion kinematics. The proposed fault tolerant control algorithm was compared with the existing satellite attitude system controllers in the literature and it was found that the proposed algorithm resulted in three axis attitude stabilization within 0.041◦ in all axes for the fault cases. The reaction wheels’ Coulomb friction, saturations, noise, dead-zones, bias fault and external disturbances are considered. Finally, a nonlinear adaptive fuzzy sliding mode controller was tested using embedded nanosatellite hardware on a frictionless spherical air bearing system. The test results showed attitude errors of 0.8◦ using the proposed controller while a proportional integral derivative controller resulted in 5◦ attitude errors.

This work deals with the design of fault-tolerant traffic control systems for urban transportation networks consisting of saturated and non-saturated intersections. A fault-tolerant control system is one that maintains system integrity (stability and vehicle flow regulation) under partial system failure brought about by local faults such as sensor/actuator failure, vehicle accidents, severing of communication links, etc. This work is motivated by the fact that, in an automated environment, vehicle and traffic control systems are highly complex. The probability and possibility of a system crash caused by local fault are also proportionately high. It is therefore desirable to incorporate fault-tolerant capabilities into a traffic network by means of suitable feedback compensation. Finally a detailed case study is also included in this work to demonstrate the properties of a fault tolerant traffic network.

In a fault tolerant control (FTC) system, a parameter varying FTC law is reconfigured according to fault parameters estimated by fault detection and isolation (FDI) modules. FDI modules require some time to detect fault occurrences in aero-vehicle dynamics. In this brief, an FTC analysis framework is provided to calculate the upper bound of an induced-L2 norm of an FTC system in the presence of false identification and detection time delay. The upper bound is written as a function of a duration time interval and exponential decay rates and has been used to determine which FTC law produces less performance degradation (tracking error) due to false identification. The analysis framework is applied for an FTC system of a highly maneuverable aircraft technology (HiMAT) vehicle

This Development of Fault Tolerant Control (FTC) systems presumes the development of a certain control method and testing it, which is not always possible in the real life and in the frames of a real technical system. Thus, it is great importance for a researcher or an engineer to have the possibility to check the proposed control method through simulation of different faults and the system's reaction on them using a set of benchmark models. These models should be complex and representative enough and allow simulation of different types of faults as well as varying the faults number and the time of occurrence. The goal of the work carried out was the creation of a convenient environment for the development of FTC systems for technical objects and complexes based on a set of benchmark representative research models for experimental testing of different approaches to diagnostics and assurance of fault-tolerant control.

This article proposes a fault tolerance control (FTC) system that composes of a state observer and a static filter, which can eliminate the adverse effects of sensor failures on the active mass damper control system of high‐rise buildings and realize fault detection and isolation. First, the accurate acceleration responses are obtained through a static filter that is used for minimizing the differences between the estimated and actual feedback signals. The key point is transformed into a gain optimization problem solved by a linear matrix inequality approach. Then, a state observer uses the detected and isolated acceleration responses as the feedback signals to estimate the whole states, which are used to calculate the control forces. Finally, a new observer‐based FTC system is accomplished for high‐rise buildings. To verify its effectiveness, the proposed methodology is applied to a numerical example and an experimental system. The results demonstrate that the fault tolerance controller has a good performance and stable control parameters, which provides good potential for structural vibration control of high‐rise buildings.

The brief instability concept in Linear Parameter Varying (LPV) systems allows the linear system to be unstable for some values of the LPV parameters so that instability occurs only for a short period of time. The present paper takes advantage of an extension of the notion of the brief instability to the LPV systems with time-delay in their dynamics to examine the performance degradation in Fault Tolerant Control (FTC) systems in the presence of false identification of the fault signals. The paper provides tools for the stability and performance analysis of such systems, where performance is evaluated in terms of induced L2-gain. The results presented in the paper demonstrate that stability and performance can be evaluated by examining the feasibility of a parameterized set of Linear Matrix Inequalities (LMIs). The paper provides the analysis conditions to guarantee the asymptotic stability and H∞ performance for FTC systems, in which instability, due to the false identification of the fault signals, is allowed to take place for a short period of time. A numerical example is presented to illustrate the qualifications of the proposed analysis and synthesis conditions for treating brief instability in the delayed FTC systems.

A fault tolerant control is mightily important in industrial and electrical vehicles. A shutdown of these motors should not happen due to its direct relationship to enormous loss to life and property, even if inter-turn fault of a winding occur. This paper proposed an inter-turn fault (ITF) tolerant control system using new-design brushless DC (BLDC) motor, which has teeth and yoke winding connected in parallel for fault tolerant control. The special point of new-design BLDC motor is that back electromotive force of teeth and yoke winding have nearly similar value and phase. In addition, we used a fault detection using input impedance algorithm. It can distinguish the ITF condition using variation of input impedance, which is obtained by monitoring of input voltage and current. After that, a fault tolerant control can prevent the spread of the fault by cutting off the three-phase winding and maintain partial output characteristics in proposed BLDC motor. The system has a special advantage that can use existing inverter without additional control device. Finally, we analyzed characteristics of the ITF tolerant control system in proposed BLDC motor using finite element method.