Passive Fault Tolerant Control Research Articles

Fault detection and fault-tolerant control of dual-motor autonomous steering system

In order to improve the safety of autonomous ground vehicle (AGV) and the accuracy of trajectory tracking, a fault detection (FD) scheme of steering system and a fault-tolerant control (FTC) method are proposed. First, this paper analyzes the causes of steering motor failure and designs a passive fault-tolerant controller to ensure that the torque motor under coordinated control can still follow the angle when a slight fault occurs in the angle motor. Second, the corresponding FD schemes are designed for different motor faults, and the unknown input observer (UIO) of the steering resistance moment is designed considering the uncertainty of the steering system caused by the fault motor. The active fault-tolerant controller composed of backstepping control and global sliding mode control (SMC) is further combined to control the fault-free motor. Finally, simulation and HiL test results show the effectiveness of the proposed FD scheme and FTC strategy.

Path tracking control for autonomous vehicles using hybrid fault-tolerant approach

Signal delay, execution deviation and reference model mismatch are common faults in autonomous vehicles, resulting in reduced path tracking control performance. To improve the path tracking performance of autonomous vehicles under fault conditions, this paper proposes a hybrid fault-tolerant (HFT) path tracking control approach, in which passive fault-tolerant path tracking control and fault observer-based hybrid active fault-tolerant path tracking control are introduced. The probable usual errors in path tracking are first examined and analyzed, together with the vehicle kinematic model and a typical autonomous driving system. Then, a slide-mode-based passive fault-tolerant path tracking controller is designed and integrated with a fault observer to create a hybrid active fault-tolerant controller. Finally, simulations and experiments are conducted, and the results demonstrate that our proposal is effective. After convergence of the fault observations, the lateral tracking error is less than 0.2m and the root mean square of the tracking error is 44% smaller than the LQR approach.

Adaptive neural network fixed-time sliding mode control for trajectory tracking of underwater vehicle

The effectiveness of Autonomous Underwater Vehicles (AUVs) in diverse underwater tasks is heavily reliant on their ability to perform accurate trajectory tracking. However, due to uncertainties in AUVs modeling and the complex underwater environment disturbances, designing effective trajectory tracking controllers and disturbance observers for AUVs is still a major challenge. To address these uncertainties and enable faster convergence of tracking errors, a trajectory-tracking controller based on fixed-time sliding mode control (FTSMC) and a Radial Basis function neural network (RBFNN) observer are used in this paper. In most cases, the AUV platform carries limited computational resources. In most cases, AUV platforms carry limited computational resources, which restricts the practical use of online neural network methods, and it is particularly important to reduce the complexity of computational neural networks and enhance the real-time performance of the observer. Therefore, we adopted a fast online weight update strategy based on a single parameter. Considering actuator faults and input saturation, passive fault-tolerant control (PFTC) is used in this scheme to further reduce the computational burden. Furthermore, the Lyapunov method is used to demonstrate the fixed-time stability of the individual signals of the system. Finally, simulation results and theoretical analysis demonstrate the superiority and effectiveness of the proposed method.

Event-based fault-tolerant [formula omitted] synchronization for inertial neural networks via a semi-Markov jump approach

In this paper, the synchronization problem of semi-Markov jump neural networks with inertial terms is studied. The semi-Markov jump (s-MJ) process is used to describe the random jump parameters in the system, so Weibull distribution is used to replace the exponential distribution of Markov jump process for the sojourn-time (ST) of each mode in the system. First, a second-order differential system is transformed into a first-order differential system by an appropriate vector substitution. Then, by applying passive fault-tolerant control techniques, the master and slave systems can be synchronized even when the controller fails. In addition, in order to reduce the waste of bandwidth, an event-triggered strategy is designed to determine whether the data needs to be transmitted. Then, by constructing a suitable Lyapunov function and using the characteristics of the cumulative distribution function, the sufficient conditions are established to ensure the stochastic stability of the closed-loop system and meet the specified H∞ performance when the controller fails. Finally, a numerical example and an image processing example are given to verify the effectiveness of the proposed method.

Design of structured [formula omitted] flight controllers: Passive fault-tolerant versus observer-based structures

This article presents the structured H∞ design and validation of two types of flight controller architectures: a passive fault-tolerant controller for the longitudinal motion and an active observer-based fault-tolerant controller for the lateral-directional motion. In the first, the controller follows the conventional Stability/Control Augmentation System (SCAS) structure, and its gains are obtained in continuous-time with the hinfstruct command by considering a set of elevator Loss-Of-Efficiency (LOE) faults. For the second, the conventional Luenberger observer-based controller structure is used, and the design aims to monitor the health of the aileron and rudder actuators in addition to provide active tolerance against LOE faults. Two different discrete-time designs are obtained for the latter, one focused on control performance optimization (using also the hinfstruct command), and the other on simultaneous control and observer performance optimization (using the systune command and under a slightly relaxed control performance constraint). For the two types of architectures, unmodeled dynamics are represented by uncertain bounded time delays modeled as pure delays or first-order Padé approximations. The resulting controllers are implemented on-board JAXA’s research airplane MuPAL-α, and not only is their practicality demonstrated but also control performance is validated via Aircraft-In-the-Loop (AIL) testing under gust-free and realistic gusty conditions. This demonstration is at a Technological Readiness Level (TRL) of 7–8, resulting in a high-level of confidence in the validity of the proposed flight control structures.

Decentralized Sensor Fault-Tolerant Control of DC Microgrids Using the Attracting Ellipsoid Method.

System stability deterioration in microgrids commonly occurs due to unpredictable faults and equipment malfunctions. Recently, robust control techniques have been used in microgrid systems to address these difficulties. In this paper, for DC-islanded microgrids that have sensors faults, a new passive fault-tolerant control strategy is developed. The suggested approach can be used to maintain system stability in the presence of flaws, such as faulty actuators and sensors, as well as component failures. The suggested control is effective when the fault is never recognized (or when the fault is not being precisely known, and some ambiguity in the fault may be interpreted as uncertainty in the system's dynamics following the fault). The design is built around a derived sufficient condition in the context of linear matrix inequalities (LMIs) and the attractive ellipsoid technique. The ellipsoidal stabilization idea is to bring the state trajectories into a small region including the origin (an ellipsoid with minimum volume) and the trajectories will not leave the ellipsoid for the future time. Finally, computational studies on a DC microgrid system are carried out to assess the effectiveness of the proposed fault-tolerant control approach. When compared with previous studies, the simulation results demonstrate that the proposed control technique can significantly enhance the reliability and efficiency of DC microgrid systems.

Active fault tolerant control based on compound iterative learning observer for trajectory tracking of autonomous underwater vehicles

This article proposes a novel active non-singular integral terminal sliding mode fault tolerant control scheme based on compound iterative learning observer (CILO-NITSM-FTC) for the trajectory tracking control problems of autonomous underwater vehicles (AUVs), which accompanied by nonlinear dynamics and possible thruster failures. The designed compound iterative learning observer (CILO) can effectively estimate the values of nonlinear dynamics and reconstruct the faults of the thrusters. Compared to the existing adaptive non-singular integral terminal sliding mode-based fault tolerant control (ANITSM-FTC), which is a passive fault tolerant control method essentially, the mentioned CILO-NITSM-FTC in this paper presents faster rate of convergence and more accurate control precision. In the design process of CILO, radial basis function neural network (RBFNN) is adopted to estimate the nonlinear dynamics, then approximation errors of neural network, thruster faults and external disturbances are considered as global disturbances. The estimated values obtained from CILO can be used to perform feedforward compensation on the designed controller to complete the reconstruction of thruster faults. Through rigorous mathematical proof and comparative numerical simulation experiments, the superiority and practicability of CILO-NITSM-FTC proposed in this paper are verified.

Nonlinear servocompensator for fault-tolerant control of a wave energy converter

This paper addresses the problem of controlling a wave energy converter (WEC) susceptible to faults in its braking subsystems, characterized through nonlinear damping. By considering the necessity of robust trajectory tracking related to the sea waves for maximizing the converted energy, one aims to preserve such a trajectory in the presence of faults to avoid physical damage in the structure of the WEC. To achieve this objective, this paper proposes a fault-tolerant control (FTC) that combines two systems: (i) a novel nonlinear servocompensator (NSC) and (ii) a fault diagnosis subsystem (FD). The NSC is based on a variable structure control that generalizes the internal model principle for robust tracking. The reference signal is computed from real-time measurements of the irregular sea waves. The FD subsystem estimates the faults related to the wear of the brakes via an unknown input observer. Due to its independent performance from the FD, the global scheme can be considered as a passive FTC. By considering the faulty model of a WEC based on the Archimedes wave swing prototype, theoretical formulation and the convergence proof are given for the NSC and the FD. The performance of the proposed design is verified with numerical simulations of the WEC with the incidence of irregular sea waves under different fault scenarios in the upper and lower brakes.

Passive fault‐tolerant control for discrete parameter system

AbstractThis study develops a passive fault‐tolerant control (FTC) method with weak conservatism for the discrete parameter system. For the first time, application of (0‐1) and symbolic parameters for describing the discrete parameter system is given. In addition, the relationship between the discrete parameter domain and the control strategy feasible set is discussed. This paper mainly discusses the significance of the intersection set of control strategy feasible sets for passive FTC. Moreover, a suggestion that the intersection set can be constructed in the absence of the intersection set by changing the topology of the controlled object or changing the controller, or combining both options is proposed. Furthermore, the conditions of obtaining a global‐optimal passive FTC strategy and a local‐optimal passive FTC strategy are analyzed, which depend on the size of the control strategy feasible set for optimizing. Finally, the simulation is carried out to show the validity of the proposed passive FTC scheme.

NONLINEAR FAULT TOLERANT CONTROL OF DUAL THREE-PHASE INDUCTION MACHINES BASED ELECTRIC VEHICLES

This paper proposes a robust fault-tolerant control (FTC) for the dual three-phase (DTP) induction machines under failures and which is controlled by a higher-order sliding mode control strategy. However, the DTP induction machine is increasingly used because of its advantages such as better reliability and supply division, both passive and active FTC laws have been designed and tested on DTP. The proposed method not only realizes the FTC and the fault elimination as well but also provides a possible solution for emulating a traction system using a direct continue machine (DCM) supplied by a four-quadrant chopper. Therefore, the emulation system is based on a controlled DCM, which imposes the same behavior of the mechanical power train of an electric vehicle to the DTP. Simulation results are given to verify the robustness and good performance of the proposed fault-tolerant control scheme.

Fault-Tolerant Control of Gas-Lifted Oil Well

The gas-lifted system has inherent ability to hide the effect of fault hence the system can inject gas into the annulus and oil will still be produced even in the presence of fault of significant value. This however affects the optimal operation of the system and could move the system towards the undesirable casing-heading instability. Faults of step decrease in the valves coefficients in addition to limitation on the valve affect the optimal flow of the liquids through the system. We detect and isolate these faults using generalised likelihood ratio test (GLRT) and Dedicated observer scheme (DOS) respectively. The states of the system are estimated using extended Kalman filter (EKF). Model predictive control based fault-tolerant control is then implemented on the system by using the robustness property of the zone control MPC and limiting the input bound in the optimiser. Both passive and active fault-tolerant control (FTC) were used to improve oil production or stabilise the system. Passive fault-tolerant control (FTC) provides more robustness but it does not change oil production noticeably enough. Reducing the upper control bound ensures stability but production could decline. Increasing the controller cost that prioritises the input target increases production but it is prone to casing-heading instability.

A Reconfiguration-Based Fault-Tolerant Control Method for Nonlinear Uncertain Systems

This article addresses reconfiguration-based fault-tolerant control (FTC) with robust guaranteed performance for nonlinear uncertain systems under actuator faults. A PAssive/ACTive combined FTC method is proposed based on reliable control, which synthesizes the advantages of the active and passive FTC and strikes a balance between the performance and complexity of the method. Moreover, the reliability overcost of this method is reduced to balance the system nominal performance and reconfigurability. In this procedure, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta$</tex-math></inline-formula> -D method is used to solve the Hamilton–Jacobi–Bellman (HJB) and generalized HJB equations. Effectiveness of the proposed method is verified by a numerical example.

Hybrid Fault-Tolerant Control for Air-Fuel Ratio Control System of Internal Combustion Engine Using Fuzzy Logic and Super-Twisting Sliding Mode Control Techniques

Safety and critical applications employ fault-tolerant control systems (FTCS) to increase reliability and availability in the event of a failure of critical components. Process facilities may employ these technologies to cut down on production losses caused by equipment failures that occur on an irregular or unscheduled basis. Air–fuel ratio (AFR) adjustment in the fuel system of internal combustion engines (ICE) is crucial for enhancing engine efficiency, saving fuel energy, and safeguarding the environment. This paper proposes a novel hybrid fault-tolerant control system (HFTCS) for controlling the AFR in ICEs that combines the features of both an active fault-tolerant control system (AFTCS) and a passive fault-tolerant control system (PFTCS). The fault detection and isolation (FDI) unit is designed using fuzzy logic (FL) as part of an AFTCS to give estimated sensor values to the engine controller when the sensor becomes faulty. Super-twisting sliding mode control (ST-SMC) is implemented as part of a PFTCS to maintain AFR by adjusting the throttle actuator in the fuel supply line under faulty conditions. Lyapunov stability analysis is also performed to make sure that the system remains stable in both normal and faulty conditions. According to the results in the Matlab/Simulink environment, the suggested system stays robust and stable during sensor faults. In faulty situations, it also maintains the AFR at 14.6 without any degradation, and a comparison with previous studies is carried out. The study shows that the suggested approach is an innovative and highly dependable solution for AFR control in ICEs, preventing engine shutdown and output loss for higher profitability.

Active Fault-Tolerant Control for Quadrotor UAV against Sensor Fault Diagnosed by the Auto Sequential Random Forest

Active disturbance rejection control (ADRC) is a model-independent method widely used in passive fault-tolerant control of the quadrotor unmanned aerial vehicle. While ADRC’s effectiveness in actuator fault treatment has been proven, its tolerance to sensor faults requires improvements. In this paper, an ADRC-based active fault-tolerant control (AFTC) scheme is proposed to control the flying attitude against sensor fault for reliability enhancement. Specifically, a semi-model-dependent state tracker is raised to reduce the influence of slow tracking, and accentuate the sensor fault even in varying maneuvers. Derived from the random forest, an enhanced method named auto sequential random forest is designed and applied to isolate and identify faults in real time. Once the tolerance compensation is generated with the fault information, a high-performance AFTC is achieved. The simulation results show that the proposed method can effectively follow the residual when a sensor fault and a change of maneuver occur concurrently. Precise fault information is obtained within 0.04 s, even for small faults on the noise level. The diagnosis accuracy is greater than 86.05% (100% when small faults are excluded), and the identification precision exceeds 97.25%. The short settling time (0.176 s when the small fault is excluded) and modest steady-state error validate the advanced and robust tolerance performance of the proposed AFTC method.

Fault-tolerant control design for unreliable networked control systems via constrained model predictive control

This work deals with the problem of passive fault-tolerant control (FTC) for discrete-time networked control systems (NCSs). Network imperfections such as random time delay and packet dropout are modeled as a Markov chain that results in a Markovian jump linear system (MJLS). Some of the elements in the transition probability matrix (TPM) are supposed to be unknown so as to address network complexities. In addition, a comprehensive and practical fault model that considers the stochastic nature of networks is employed. By utilizing this fault model, the closed-loop NCS model is obtained by means of state augmentation technique. Then, a constrained model predictive control (MPC) is proposed to develop a fault-tolerant control strategy in which all these issues are considered as well as input constraint. Sufficient conditions to design the proposed reliable controller are derived in terms of linear matrix inequalities (LMIs). Finally, two examples are utilized to demonstrate the validity of the proposed FTC. The simulation results show that the proposed strategy works well, and results in more effective responses compared to state-of-the-arts studies.

Design of a Hybrid Fault-Tolerant Control System for Air–Fuel Ratio Control of Internal Combustion Engines Using Genetic Algorithm and Higher-Order Sliding Mode Control

Fault-tolerant control systems (FTCS) are used in safety and critical applications to improve reliability and availability for sustained operation in fault situations. These systems may be used in process facilities to reduce significant production losses caused by irregular and unplanned equipment tripping. Internal combustion (IC) engines are widely used in the process sector, and efficient air–fuel ratio (AFR) regulation in the fuel system of these engines is critical for increasing engine efficiency, conserving fuel energy, and protecting the environment. In this paper, a hybrid fault-tolerant control system has been proposed, being a combination of two parts which are known as an active fault-tolerant control system and a passive fault-tolerant control system. The active part has been designed by using the genetic algorithm-based fault detection and isolation unit. This genetic algorithm provides estimated values to an engine control unit in case of a fault in any sensor. The passive system is designed by using the higher-order sliding mode control with an extra fuel actuator in the fuel supply line. The performance of the system was tested experimentally in MATLAB/Simulink environment. Based on the simulation results, the designed system can sustain the AFR despite sensor failures. A new method of managing the AFR of an IC engine has been demonstrated in this study, and it is highly capable, robust, reliable, and highly effective. A comparison with the existing works found in the literature also proves its superior performance. By inserting the fault in each sensor, it was clearly observed that proposed HFTCS was much better than the existing model as it was more fault-tolerant due to its ability to work in both online and offline modes. It also provided an exact value of 14.6 of AFR without any degradation.

Adaptive dynamic surface output feedback control for a class of quadrotor aircraft with actuator faults

PurposeThe purpose of this study is to propose an adaptive fault-tolerant control approach based on output feedback for a class of quadrotor unmanned aerial vehicles system. In the event of a controlled actuator failure, a stable flying of the aircraft can be achieved by selecting an appropriate sliding mode surface.Design/methodology/approachAiming at the actuator failure of quadrotor aircraft during flight in the controllable range, a dynamic surface sliding mode passive fault-tolerant controller based on output feedback is designed based on the strong robustness of sliding mode method. Due to the unknown nonlinearity dynamics and parameter uncertainties in the system, a nonlinear observer is used to estimate them online.FindingsThe stability of the suggested algorithm is established using appropriate Lyapunov functions, and the performance of the proposed control approach is demonstrated using hardware-in-the-loop simulation.Originality/valueAn error performance function is introduced into the controller to ensure the convergence speed and accuracy of errors are within the predetermined range. By using the norm estimation method, there is only one parameter that needs to be updated in each step of the control process, which considerably minimizes the calculation burden. Finally, the validity of the proposed control scheme is verified on the hardware-in-the-loop simulation, and the results show that the proposed control method has achieved the desired results.

Passive Control Tolerant to Sensing Faults in dynamic compensation devices - SVC through a hybrid strategy

For this research, a passive fault tolerant control system is developed for a static reactive compensator coupled to a microgrid in connected mode, oriented to those faults that result as a consequence of common damages in their sensing systems. The proposed method uses a robust optimal controller by H and artificial neural networks as a nonlinear estimation method. Simulations, validation, plant identification and controller design are carried out using a microgrid Benchmark system, programmed in Matlab/Simulink. The research shows valuable results such as: the improvement in the reliability and resilience of static compensators against sensing failures, improvements in the behavior of the output signal of the static compensator controller exposed to sensing failures and the decrease in error with respect to classic controller.

A comprehensive review of fault diagnosis and fault-tolerant control techniques for modular multi-level converters.

Many faults occur in the modular multi-level converters (MMCs), including unbalancing capacitor voltage, lower and upper arm unbalancing, the line to line voltage unbalancing, sensors and actuators fault, system fault, and sub-modules fault in high as well as medium voltage applications. Several fault-tolerant approaches are presented to overcome these problems, such as active fault-tolerant control system (AFTCS), passive fault-tolerant control system (PFTCS), hybrid fault-tolerant control system (HFTCS), redundant system technique, special power circuit with the controller, and zero sequence voltage methods, which we will explain extensively in this article. This review emphasizes the types of faults in the MMCs and discusses the protection methods under failure conditions. The MMC is more popular in high voltage applications because it not only improves the quality of the grid but also has good harmonic performance in high power transmission. There is no need for any isolated dc sources to operate it. When faults are removed, the efficiency and reliability of the system will be increased. This extensive explanation of the current literature on MMC fault diagnosis and control techniques will conclude which methods provide a more valuable solution. Finally, this paper discusses the best approach to reduce MMC faults and provides a future research direction to the readers.

Active and passive fault tolerant control allocation strategy for nonlinear systems

This article introduced fault-tolerant control (FTC) schemes for over-actuated affine non-linear uncertain systems. The proposed methodologies incorporate two different control allocation (CA) units with high-level nonlinear adaptive sliding mode control (NLASMC) strategy. The first FTC strategy is active that utilizes an online CA unit to effectively manage the redundant actuators towards the chosen flight path in faulty conditions. On the other hand, the second FTC scheme is passive based on the idea of a fixed CA scheme and does not require control-input reconfiguration during the faulty condition. A robust NLASMC law is selected to enforce the state trajectories converges to the sliding manifold despite the uncertainty in the model dynamics and external disturbance effect. The proposed schemes are then applied to the nonlinear F16 aircraft detailed model equipped with thrust vectoring (TV) control. The nonlinear simulations on 6-degree-of-freedom (6-DOF) F16 aircraft are performed under the failure of the aileron, rudder, and elevator. It can be visualized that both schemes performed well, but online CA scheme can cope with more faults and failures combinations in comparison to fixed CA schemes. Furthermore, both FTC approaches performed well when compared to existing methods in the literature.