Fault-tolerant Control Theory Research Articles

Defending State-Feedback Based Controllers Against Sensor Attacks

Context: This paper is motivated by the need to improve the resilience of industrial control systems. Many control systems currently operating in the industry were designed and implemented before the boom in communications (wired and wireless networks) within industrial control systems. However, nowadays they operate connected to the communications network. This increase in connectivity has made the systems susceptible to cyber-attacks that seek to degrade the proper operation of the control loop even affecting only one sensor.
 Method: We use concepts from fault tolerant control and classic control theory to show that it is possible to reconstruct the system state without (any) one of the system outputs. This fact is used in the recalculation of the control signal through an algorithm of attack detection and isolation, to avoid for an attack to be feedback to the system, mitigating its effect. We show the effectiveness of our proposal with simulations on a four-tanks testbed using Matlab and Simulink.
 Results: We show that a bank of unknown input observers can be designed to recover true information from attacked sensors, i.e., recover the information without the effect of the attack. Therefore, the estimation obtained from those observers can be utilized for computing a control action that mitigates the effect of the attack.
 Conclusions: This mitigation of the attack prevents a single sensor attack from signi cantly impair the action of low-level controllers, improving the resilience on the system just modifying the digital controller architecture. The development presented is limited to cyber-attacks on system sensors pre- sented one at a time, that still can compromise seriously the system behavior. Future work will address the extension of the presented results in situations with simultaneous attacks on more than one sensor, and/or consider attacks on the control system actuators.

Fault tolerant attitude control of under-actuated spacecraft: Theory and experiment

This paper investigates fault tolerant attitude control theory and experiment for under-actuated spacecraft with one reaction wheel completely broken and two others suffering actuator faults of partial loss of effectiveness or bias. A non-smooth robust adaptive fault tolerant control law is proposed under the zero-momentum and input saturation conditions. It shows that the available reaction wheels need to produce sufficient control torque for the fault tolerance. Such a new control method is implemented in a semi-physical simulation system of an air-bearing platform. Experimental results show the effectiveness of the proposed method in spacecraft practical engineering.

Fault-tolerant control based on fractional sliding mode: Crawler plant protection robot

Accurate control of driving system for crawler plant protection robot (CPPR) is a challenging problem in smart agriculture. The soil is usually soft and mixed with straw and weeds in field. When the CPPR is in contact with the soil, uncertain shear disturbance will occur due to pressure subsidence and shear action. In serious cases, it may even lead to failure, which significantly increases the control difficulty. In this paper, a fractional order sliding mode fault tolerant (FSMFT) control based on online real-time fault estimation is proposed. Firstly, the fault model of the driving system is established, and a fault observer based on nonlinear fault observer (NFO) is designed according to the fault model, which can estimate the fault information of the driving system in real time online. Then, a fractional order sliding mode (FOSM) fault tolerant control method is proposed according to the observation information of the observer. It will be shown that by incorporating fault tolerant control theory and the observer technique, the proposed control can ensure a good control performance in terms of tracking precision, robustness, and fast convergence, etc. Finally, simulation experiments are demonstrated to show the superiority of the proposed control algorithm.

The preview control of a class of linear systems and its application in the fault-tolerant control theory

ABSTRACTIn the fault-tolerant control theory based on model following control, the desired signal of the control system is the output of a reference system. This paper is concerned with the design of the preview controller for a class of fault systems. A composite vector is introduced by including error vector, fault system state vector and reference system state vector. Then, we derived an augmented system from the known system equation, in which the reference input has equal status with the desired signal in the traditional preview control theory. Therefore, we can use the known theory to design the preview controller for the augmented system, then the preview controller of the original fault system can be obtained by the integration method. This paper strictly discusses the connection between stabilisation and detectability of the augmented system and the corresponding characteristics of the original system. Finally, by applying this theory to a real steam generator water level control system, it is found that the actions of the reference input preview and the fault signal preview can effectively eliminate the effect of the fault signal on the water level of the steam generator. The simulation shows the effectiveness of the controller designed.

Observer-Based Decentralized Adaptive NNs Fault-Tolerant Control of a Class of Large-Scale Uncertain Nonlinear Systems With Actuator Failures

In this paper, we are concerned with the fault-tolerant control (FTC) issue for a class of large-scale uncertain multi-input and multioutput nonlinear systems. The features of such class of systems are that virtual control variables are in nonaffine pure-feedback form and actuator failures consist of both lock-in-place and loss of effectiveness. We develop an adaptive observer to reconstruct unavailable state information for this class of systems taking advantage of the universal approximation property of neural networks (NNs). And then, an observer-based decentralized adaptive FTC strategy is designed recursively by combining backstepping methods with NNs, FTC theory as well as the dynamic surface control (DSC) technique. The superiorities of this proposed strategy are that it is only dependent on output information of the system and there is no requirement for accurate parameters of the system. It is also hardly inevitable that repeat differentiation calculations of virtual functions with the help of DSC technology. In theory, the stability of the resulting closed-loop system is rigorously investigated, and it is proven that all signals remain uniformly ultimately bounded and tracking errors converge to a small neighborhood around the origin by suitable choice of design parameters. Finally, simulation results, both practical and numerical examples, are illustrated to verify the feasibility of the theoretical claims.

Adaptive Minimum-Entropy Hybrid Compensation for Compound Faults of Non-Gaussian Stochastic Systems

This study investigated minimum-entropy hybrid fault-tolerant control (FTC) theory for non-Gaussian stochastic systems with compound faults. After fuzzy linearization for the singular systems, the output probability density function (PDF) is generated by rational square root B-splines. To deal with the compound faults consisting of single sensor fault and intermittent multiple actuator faults, an active-passive hybrid adaptive FTC scheme is proposed: A passive compensation function can directly reconstruct the algorithm to mask the sensor fault; then, actuator fault estimation accurately tracks the multiple actuator faults. Hence, the hybrid FTC combines estimated information and passive compensation simultaneously implements active actuator fault repair and passive sensor fault shielding. A novel variable parameter algorithm that mimics animal predation behavior is designed and incorporated into learning rates, making the controller more sensitive to the incipient deviations in actuator faults. Finally, with the optimal indicators containing entropy and mean of non-Gaussian PDF, the minimum-entropy FTC is achieved. Lyapunov and indicator functions prove the stability, simulation verifies the effectiveness of the methods.

Adaptive Sliding Mode Control for High-Frequency Sampled-Data Systems with Actuator Faults

This paper investigates the sliding mode control for high-frequency sampled-data systems with actuator faults. Besides matched nonlinearity, this paper also considers unmeasurable states and unknown actuator degradation ratio as important factors of the overall system. The estimates of system state vector are obtained by an adaptive sliding mode observer method firstly. Then, a novel integral-type sliding surface, corresponding to the unified closed-loop delta operator system, is provided based on aforementioned estimation values, and the fault closed-loop system is proven to be stable by the proposed sliding mode control law. Finally, the fault-tolerant control theory is verified to be valid via a practical simulation example.

Support technology for safe preventive maintenance of control systems

On the basis of fault-tolerant control theory and switching L2 gain analysis, we propose a new maintenance support technology to implement an operating state suitable for safely performing preventive maintenance of each subsystem, where the safety of the bidirectional transitions between normal operation and an operating state is guaranteed.

Command-filter-based distributed containment control of nonlinear multi-agent systems with actuator failures

ABSTRACTIn this paper, the problem of distributed containment fault-tolerant control for a class of nonlinear multi-agent systems in strict-feedback form is studied. The considered nonlinear multi-agent systems are subject to unknown nonlinear functions and actuator faults with loss of effectiveness and lock-in-place. By resorting to the universal approximation capability of fuzzy logical systems, the command filtered backstepping technique and nonlinear fault-tolerant control theory, distributed controllers are designed recursively. From the Lyapunov stability theory, it is proved that all signals of the resulting closed-loop systems are cooperatively semi-globally uniformly ultimately bounded and the containment errors converge to a small neighbourhood of origin by properly tuning the design parameters. Finally, a numerical example is provided to show the effectiveness of the proposed control method.

Fault tolerant quantum filtering and fault detection for quantum systems

This paper aims to determine the fault tolerant quantum filter and fault detection equation for a class of open quantum systems coupled to a laser field that is subject to stochastic faults. In order to analyze this class of open quantum systems, we propose a quantum–classical Bayesian inference method based on the definition of a so-called quantum–classical conditional expectation. It is shown that the proposed Bayesian inference approach provides a convenient tool to simultaneously derive the fault tolerant quantum filter and the fault detection equation for this class of open quantum systems. An example of two-level open quantum systems subject to Poisson-type faults is presented to illustrate the proposed method. These results have the potential to lead to a new fault tolerant control theory for quantum systems.

A Class of Uncertain Networked Control Systems with Robust <i>H<sub>∞</sub></i> Fault-Tolerant

T For the networked control system (NCS), the considered system has actuator and sensor failures. In considering the impact of the network delay on system performance, establish a new class of uncertain NCS fault model Then use Lyapunov stability theory, fault-tolerant control theory and the static state feedback, the sufficient conditions for closed-loop NCS possessing robust asymptotically stable against actuator and sensor failure are given . And the robust H-inf fault-tolerant controller design method under the sensor and actuator failures is deduced in terms of linear matrix inequalities (LMI). An numerical simulation is provided to show the effectiveness of the proposed conclusion.

Robust <i>Η<sub>∞</sub></i> Fault-Tolerant for a Class of Networked Control System Based on Static Output Feedback

This paperfocuses on the networked control system (NCS) with sensor and actuatorfailures, considering the impact of the network delay and parameter uncertaintyon system performance, We propose a design of robust Η∞ fault-tolerant control based on static outputfeedback .The closed- loop networked control system possessing asymptoticallystable is given by staticoutput feedback, fault-tolerantcontrol theory and Lyapunov stability theory. Then the fault-tolerant controller is deduced by using linear matrixinequalities. Numerical simulation illustrates the method has a good robustfault tolerant capability that the conclusions are valid.

Observer-based fuzzy adaptive control of nonlinear systems with actuator faults and unmodeled dynamics

In this paper, an adaptive fuzzy output feedback fault-tolerant control scheme is developed for a class of nonlinear systems with actuator faults, unmodeled dynamics and without assuming the states being available for control design. Fuzzy logic systems are employed to approximate unknown nonlinear functions, and a fuzzy state observer is established to estimate the unmeasured states. By combining adaptive backstepping technique with changing supplying function technique and the nonlinear fault-tolerant control theory, a novel adaptive fuzzy fault-tolerant output feedback control approach is developed. It is proved that proposed control approach guarantees that all the variables of the closed-loop system are bounded. The simulation results are provided to illustrate the effectiveness of the proposed control approach. Compared with the existing results, the main contributions of this paper are as follows: (1) the proposed control method removes the restrictive assumption that all the states of the controlled system be measured directly; and (2) the proposed control method cannot only compensate for the actuator faults, but also solve the problem of the unmodeled dynamics.

Observer-based adaptive fuzzy fault-tolerant output feedback control of uncertain nonlinear systems with actuator faults

This paper develops an adaptive fuzzy control method for accommodating actuator faults in a class of unknown nonlinear systems with unmeasured states. The considered faults are modeled as lock-in-place (stuck at unknown place). With the help of fuzzy logic systems to approximate the unknown nonlinear functions, and K-filters are designed to estimate the unmeasured states. Combining the backstepping technique with the nonlinear fault-tolerant control theory, a novel adaptive fuzzy faults-tolerant control (FTC) approach is constructed. It is proved that the proposed control approach can guarantee that all the signals of the resulting closed-loop system are bounded and the tracking error between the system output and the reference signal converges to a small neighborhood of zero by appropriate choice of the design parameters. Simulation results are provided to show the effectiveness of the control approach.

Research on Sensor Fault-Tolerant Control Based on Riccati Equation for Electric Power Steering

In order to ensure the safe and reliable operation of electric power steering(eps) system,the fault-tolerant control theory is used to design the feedback control for eps system and the control rule for sensor failure in the linear continuous system is described.On the basis of riccati equation,the design method and steps of fault-tolerant controller are given from the view of optimal control.By taking electric power steering of a certain mini car as research object,the simulation calculation is carried out.By applying such fault-tolerant controller for the eps system,the simulation results show that the system has no sensitiveness to the sensor faults,and the method can satisfy the demand of fault-tolerant control.

Robust Reliability Design for Networked Control Systems Based on Information Scheduling

This document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.Networked Control Systems (NCS) are systems with at least one loop closed through data networks. The existence of real-time network in the feedback control loop makes it more complex to analyze and design the NCS. In this paper, the networked control systems with network-induced delay, parameters uncertainty and packet loss which are induced by the limited bandwidth of communication networks is modeled, consider the sensors that can’t send information to controller and the actuators that can’t receive information calculated and sent by the controller, the integrity design of the networked control system with sensors failures and actuators failures is analyzed based on information scheduling and robust fault-tolerant control theory. Sufficient conditions, based on Lyapunov function method, are established in terms of linear matrix inequalities (LMIs). When these LMIs are feasible, the explicit expression of the controller can also be characterized. After detailed theoretical analysis, the simulation results is provided, which further demonstrated the proposed scheme.

Robust Reliability Design for Networked Control Systems Based on State Observers

Networked control systems with network-induced delay, packet loss and parameters uncertainty is modeled in this paper, consider the sensors that can’t send information to controller and the actuators that can’t receive information calculated and sent by the controller, the integrity design of the networked control system with sensors failures and actuators failures is analyzed based on robust fault-tolerant control theory. Parametric expression of controller is given based on feasible solution of linear matrix inequality. After detailed theoretical analysis, the simulation results is provided, which further demonstrated the proposed scheme.

A robust fault-tolerant control strategy for networked control systems

Networked control systems (NCS) are one type of distributed control systems where serial communication networks is used to exchange system information and control signals between various physical components of the systems that may be physically distributed. The existence of real-time network in the feedback control loop makes analysis and design of an NCS complex, and conventional control theories such as synchronized control and non-delayed sensing and actuation must be reevaluated prior to application to networked control systems. NCS is a kind of feedback control systems where the control loops are closed through real-time control network. The performance of the closed-loop system is not only determined by the characteristics of the control system, but also determined by the scheduling manner imposed by network. In this paper, adjustable deadbands are explored as a solution to reduce network traffic in networked control systems and we presented a new modeling method for networked control systems with random time delays and communication constraints based on quasi-T–S fuzzy models. The integrity design for the kind of networked control systems is analyzed based on robust fault-tolerant control theory and information scheduling. Parametric expression of controller is given based on feasible solution of linear matrix inequality (LMI). After detailed theoretical analysis, this paper also provides the simulation results, which further validate the proposed scheme.

Adaptive Cruise Control Using Sensor Fault-Tolerant Control

In order to ensure the safe and reliable operation of adaptive cruise control (ACC) system, the fault-tolerant control theory is used to design the feedback control for acc system and the control rule for sensor failure in the linear continuous system is described. On the basis of riccati equation, the design method and steps of fault-tolerant controller are given from the view of optimal control. By taking adaptive cruise control of a certain mini car as research object, the simulation calculation is carried out. By applying such fault-tolerant controller for the acc system, the simulation results show that the system has no sensitiveness to the sensor faults, and the method can satisfy the demand of fault-tolerant control.

Research on robust fault-tolerant control for networked control system with packet dropout

Abstract A kind of networked control system with network-induced delay and packet dropout, modeled on asynchronous dynamical systems was tested, and the integrity design of the networked control system with sensors failures and actuators failures was analyzed using hybrid systems technique based on the robust fault-tolerant control theory. The parametric expression of controller is given based on the feasible solution of linear matrix inequality. The simulation results are provided on the basis of detailed theoretical analysis, which further demonstrate the validity of the proposed schema.