Passive Fault Tolerant Control Research Articles

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.

A metaheuristic approach for interval type-2 fuzzy fractional order fault-tolerant controller for a class of uncertain nonlinear system*

A new optimum interval type-2 fuzzy fractional-order controller for a class of nonlinear systems with incipient actuator and system component faults is introduced in this study. The faults of the actuator and system component (leak) are taken into account using an additive model. The Interval Type-2 Fuzzy Sets (IT2FS) is used to design an optimal fuzzy fractional order controller, and two different nature inspired metaheuristic algorithms, Follower Pollination Algorithm (FPA) and Genetic Algorithm (GA), are used to optimize the parameters of the fuzzy PID controller and Interval Type-2 Fuzzy Tilt-Integral-Derivative Controller (IT2FTID) for nonlinear system. The suggested control approach consists of two parts: an Interval Type-2 Fuzzy Logic Controller (IT2FLC) controller and a fractional order TID controller. Additionally, the two inputs of the IT2FLC are also calibrated using two fine tuning parameters and , respectively. The stability of the proposed controller is presented with some conditions. In addition to unknown dynamics, some unknown process disturbances, such as rapid changes in the control variable, are taken into account to check the efficacy of the proposed control scheme. Two nonlinear conical two-tank level systems are used in the simulation as a case study. The performance of the suggested approach is also compared to that of a widely recognized Interval Type-2 Fuzzy Proportional-Integral-Derivative (IT2FPID) Controller. Finally, the proposed control scheme's fault-tolerant behaviour is demonstrated using fault-recovery time results and statistical Z-tests for both controllers, and the proposed IT2FTID controller's effectiveness is demonstrated when compared to IT2FPID and existing passive fault tolerant controllers in recent literature.

Robust finite-time fault-tolerant control for dynamic positioning of ships via nonsingular fast integral terminal sliding mode control

A passive sliding-mode fault-tolerant control (FTC) scheme is developed in this paper for the dynamic positioning (DP) of ships to guarantee closed-loop finite-time stability in the presence of an actuator fault, a parameter uncertainty in the system and an unknown external disturbance. First, a novel nonsingular fast integral terminal sliding mode (NFITSM) which has more faster convergence rate and less chattering behavior is proposed to eliminate the singularity completely. Second, by integrating the proposed NFITSM and finite-time stability theory, a passive fault-tolerant controller is developed. Based on Lyapunov stability theory, global finite-time convergence of sliding mode and tracking errors is proved. A novel adaptive law is proposed to cope with real sliding mode constraints. Finally, the results of numerical simulation show that the proposed fault-tolerant controller successfully achieves good performance.

Overlapping Decentralized Control Strategies of Building Structure Vibration Based on Fault-Tolerant Control under Seismic Excitation

The vibration control system of a building structure under a strong earthquake can be regarded as a large complex system composed of a series of overlapping subsystems. In this paper, the overlapping decentralized control of building structure vibration under seismic excitation is studied. Combining the overlapping decentralized control method, H∞ control algorithm, and passive fault-tolerant control method, a passive fault-tolerant overlapping decentralized control method based on the H∞ control algorithm is proposed. In this paper, the design of robust H∞ finite frequency passive fault-tolerant static output feedback controller for each subsystem is studied. The fault matrix of the subcontroller is expressed by a polyhedron with finite vertices. In order to reduce the influence of external disturbance on the controlled output, the finite frequency H∞ control is adopted and the Hamiltonian matrix is avoided. In this paper, the passive fault-tolerant overlapping decentralized control method based on H∞ control algorithm is applied to the vibration control system of the four-story building structure excited by the Hachinohe seismic wave. One drive is set on each layer of the structure, and a total of four drives are set. Select the driver fault factor of 0.5 or 1 and the frequency band [0.3, 8] Hz. The overlapping decentralized control scheme and 16 fault-tolerant fault matrices are designed, and the numerical comparison results are given. The results show that both overlapping decentralized control strategy and multioverlapping decentralized control strategy have achieved good control results. Due to the different number of subsystems and overlapping information, the overlapping decentralized control scheme increases the flexibility of controller setting and reduces the computational cost.

Adaptive Fault Tolerant Attitude Control of a Nano-Satellite with Three Magnetorquers and One Reaction Wheel

In this paper, a passive fault tolerant attitude control is investigated for a nano-satellite with three magnetorquers and one reaction wheel in the presence of actuator constraints, external disturbances, and partial loss of actuator effectiveness as unknown actuator faults. For this purpose, a variable structure control approach is employed due to its ability to deal with the partial loss of actuator effectiveness and adjusting the maximum amplitude of the control signal by a control gain. A modified sliding variable is designed based on angular velocity and attitude errors with an adaptive parameter coefficient. The dynamics equation of the adaptive parameter is extracted during the stability proof of the closed-loop system. Changing the value of this parameter changes the effect intensity of the quaternion errors on the sliding variable and causes the attitude errors to maintain within a limited range. Applying this parameter to the modified sliding variable makes the controller perform well even if the adaptive parameter is significantly reduced. Furthermore, directly using the adaptive parameter in the structure of control law makes the controller generate a chattering-free torque. Comparing the simulation results with the results of two variable structure control methods designed in previous articles shows that its performance in attitude tracking commands has improved. In addition, Monte Carlo simulations with random actuator faults are performed to show the robustness of the proposed controller in the presence of actuator constraints and external disturbances.

CURRENT STATUS OF CONTROL STRATEGIES IN ENERGY RECOVERY SYSTEMS IN ELECTRIC VEHICLES

There is currently an increasing demand for electric vehicles that require greater autonomy and energy efficiency when driving them. Control strategies in energy recovery systems are crucial to optimize the amount of energy returned to the battery and to ensure safety and stability for the user. In this paper, active fault tolerant control systems (AFTC) and passive fault tolerant control systems (PFTC) with other specialized control strategies (Fuzzy Logic, Neural Networks and Perturbation Rejection Controllers) are compared with classical PID controllers.The results of the simulations show that, keeping the battery voltage constant, returns of about 12% of the battery charge capacity are achieved while the braking time of the vehicles is reduced.

Distributed Passive Fault Tolerant Formation Tracking for Uncertain Second Order Multi-Agent Systems

This paper deals with the problem of distributed passive fault tolerant formation tracking control for cooperative second order multi-agent systems (MASs) subject to disturbances and sensor/actuator faults. The proposed scheme is based on decentralized observers used to robustly estimate the actuator and sensor faults in spite of disturbances. These estimates are then injected into a dynamic control law in order to mitigate their effects on the control objective. Using the Hco method, graph theory properties and the projection lemma, sufficient conditions in the form of a set of linear matrix inequalities (LMIs) are derived to guarantee the stabilization of the tracking errors while reducing the effects of sensor and actuator faults and disturbances. A numerical simulation illustrates the effectiveness of the proposed passive fault-tolerant control scheme.

Passive Fault-Tolerant Control of a 2-DOF Robotic Helicopter

The presence of faults in dynamic systems causes the potential loss of some of the control objectives. For that reason, a fault-tolerant controller is required to ensure a proper operation, as well as to reduce the risk of accidents. The present work proposes a passive fault-tolerant controller that is based on robust techniques, which are utilized to adjust a proportional-derivative scheme through a linear matrix inequality. In addition, a nonlinear term is included to improve the accuracy of the control task. The proposed methodology is implemented in the control of a two degrees of a freedom robotic helicopter in a simulation environment, where abrupt faults in the actuators are considered. Finally, the proposed scheme is also tested experimentally in the Quanser® 2-DOF Helicopter, highlighting the effectiveness of the proposed controller.

Interval observer-based methodology for passive fault tolerant control of linear parameter-varying systems

The paper deals with passive fault tolerant control for linear parameter varying systems subject to component faults. Under the assumption that the faults magnitudes are considered unknown but bounded, a novel methodology is proposed using interval observer with an [Formula: see text] formalism to attenuate the effects of the uncertainties and to improve the accuracy of the proposed observer. The necessary and sufficient conditions of the control system stability are developed in terms of matrix inequalities constraints using Lyapunov stability theory. Based on a linear state feedback, a fault tolerant control strategy is designed to handle component faults effect as well as external disturbances and preserve the system closed-loop stability for both fault-free and component faulty cases. Two simulation examples are presented to demonstrate the effectiveness of the proposed method.

Encryption–decryption-based consensus control for multi-agent systems: Handling actuator faults

This paper deals with the encryption–decryption-based passive fault-tolerant consensus control problem for a class of linear multi-agent systems subject to loss-of-effectiveness and additive actuator faults. Both the secure communication and fault tolerance issues are investigated, and their impacts on the consensus are examined. To ensure the communication security, two encryption–decryption-based fault-tolerant consensus control schemes are proposed, with which the original state of the local agent is first encrypted into a series of codewords and then decrypted by other agents to realize data privacy preserving. The necessary and sufficient condition is established for the addressed consensus problem under the adopted controller structure. A series of numerical examples are given to verify the effectiveness of the developed consensus control strategy.

A hybrid fault-tolerant control strategy for four-wheel independent drive vehicles

In this paper, a hybrid fault-tolerant control strategy is putted forward to improve the stability of the four-wheel independent drive (4WID) electric vehicle with motor failures. To improve the handling performance of the vehicle with in-wheel motor failures, the faults of in-wheel motors are analyzed and modeled. Then, a model reference adaptive fault observer was designed to observe the faults in real-time. Based on the observation results, there are designed a model predictive control (MPC) based high-performance active fault-tolerant control (AFTC) strategy and a sliding mode control based high-robust passive fault-tolerant control (PFTC) strategy. However, the fault observation results may not always be accurately. For this circumstance, a hybrid fault-tolerant control strategy was designed to make the control method find a balance between optimality and robustness. Finally, a series of simulations are conducted on a hardware-in-loop (HIL) real-time simulator, the simulation results show that the control strategy designed in this paper is effectiveness.

Adaptive event-based robust passive fault tolerant control for nonlinear lateral stability of autonomous electric vehicles with asynchronous constraints

This work solves the robust passive fault-tolerant control problem for autonomous electric vehicles based on an adaptive event triggered mechanism. Firstly, given the system uncertainties from the tire dynamics and the longitudinal speed, the T–S fuzzy model method is used to approximate the vehicle lateral dynamics. Secondly, taking the communication constraints caused by band-limited networks into account, an adaptive event-triggered scheme is introduced in the process of the control design. Moreover, the asynchronous constraint of the weight function between the controller and system is considered. Thirdly, considering that the actuator faults are inevitably encountered in the control system, a robust passive fault-tolerant control method is proposed to improve vehicle performances. Finally, simulations are carried out to illustrate the effectiveness and robustness of the proposed approach.

TRACKING CONTROL AND STABILIZATION OF A FRACTIONAL FINANCIAL RISK SYSTEM USING NOVEL ACTIVE FINITE-TIME FAULT-TOLERANT CONTROLS

This paper introduces a fractional-order financial risk system for the first time. Employing well-known tools and analyses such as bifurcations diagrams and spectral entropy, the dynamical behaviors of the system associated with fractional derivative are investigated. The impacts of the fractional derivative on the system’s behavior and its dynamical feature are shown. Then, tracking control and stabilization of the systems are studied. As it is obvious, the existence of faults and failures in the process of control of financial and economic systems is undeniable — this issue necessitates applying proper control techniques for the systems. So as to achieve appropriate results in the control of fractional financial risk system, two finite-time fault-tolerant controllers are proposed, namely, finite-time active fault-tolerant control and finite-time passive fault-tolerant control. Not only do these techniques force the system to reach desired values in finite time, but also, the proposed techniques are robust against uncertainties, faults, and failures in actuators. Through finite-time observers, the effects of all uncertainties are taken to account in the active controller. Finally, numerical simulations of tracking control and stabilization are presented. For numerical simulations, the fractional financial risk system is considered to be in the presence of unknown disturbance as well as faults and failures in actuators. It is assumed that the system is in the presence of various types of actuator faults. Numerical results affirm the ability of the offered control techniques for pushing the states of the fractional-order risk system to the desired value in a short period of time.

An integrated fault-tolerant control strategy for control surface failure in a fighter aircraft

AbstractElevator failure may have fatal consequences for fighter aircraft that are unstable due to their high manoeuvrability requirements. Many studies have been conducted in the literature using active and passive fault-tolerant control structures. However, these studies mostly include sophisticated controllers with high computational load that cannot work in real systems. Considering the multi-functionality and broad operational prospects of fighter aircraft, computational load is very important in terms of applicability. In this study, an integrated fault-tolerant control strategy with low computational load is proposed without sacrificing the ability to cope with failures. This control strategy switches between predetermined controllers in the case of failure. One of these controllers is designed to operate in a non-failure condition. This controller is a basic controller that requires very little computational effort. The other controller operates when an asymmetric elevator failure occurs. This controller is a robust fault-tolerant controller that can fly the aircraft safely in case of elevator failure. The switching is decided by a failure detection system. The proposed integrated fault-tolerant control system is verified by non-linear F-16 flight simulations. These simulations show that the proposed method can cope with failures but requires less computational load because it uses a conventional controller in the case of no failure.

Dynamics estimator based robust fault-tolerant control for VTOL UAVs trajectory tracking

This paper investigates the control issue of the trajectory tracking of vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) in the presence of partial propeller fault and external disturbance. In particular, a robust passive fault-tolerant control strategy is proposed by introducing a first-order filter based dynamics estimator. First, a bounded force command is exploited by employing a new smooth saturation function in the output of the estimator. A sufficient condition in terms of a specified parameter selection criteria is provided to ensure the non-singularity extraction of the command attitude. Then, a torque command is applied to the attitude loop tracking. Since there is merely one filter parameter involved in the dynamics estimator, the practical implementation and parameter tuning can be significantly simplified. Stability analysis indicates that the proposed control strategy guarantees the semi-globally ultimately bounded tracking of VTOL UAVs subject to partial propeller fault and external disturbance. Simulation and experiment results with comparison examples are performed to validate the effectiveness of the proposed strategy. Experimental results show that the proposed strategy achieves the trajectory tracking with a good performance (mean deviation 0.0074 m and standard deviation 0.1202 m) in the presence of 35% propeller fault and 4 m/s persistent wind disturbance.

Incremental Twisting Fault Tolerant Control for Hypersonic Vehicles With Partial Model Knowledge

A passive fault tolerant control scheme is proposed for the full reentry trajectory tracking of a hypersonic vehicle in the presence of modeling uncertainties, external disturbances, and actuator faults. To achieve this goal, the attitude error dynamics with relative degree two is formulated first by ignoring the nonlinearities induced by the translational motions. Then, a multivariable twisting controller is developed as a benchmark to ensure the precise tracking task. Theoretical analysis with the Lyapunov method proves that the attitude tracking error and its first-order derivative can simultaneously converge to the origin exponentially. To depend less on the model knowledge and reduce the system uncertainties, an incremental twisting fault tolerant controller is derived based on the incremental nonlinear dynamic inversion control and the predesigned twisting controller. In this article, it is shown that not only the benefits of both incremental control and twisting control are inherited, but also their side effects are reduced. Notably, the proposed controller is user friendly in that only fixed gains and partial model knowledge are required. Numerical simulations in various cases and comparison studies are conducted to verify the effectiveness of the proposed method.

Dual multivariable model-free adaptive individual pitch control for load reduction in wind turbines with actuator faults

Thanks to the great advances in the installations of large wind turbines, individual pitch control (IPC) has gained mounting interest among researchers. The actuator faults, however, have become a hindrance with the individual pitch process introducing more actuator actions and the pitch system operating in complex conditions. The traditional fault-tolerant control strategies of the IPC, which are mainly based on the system modeling information, and require the process of fault diagnosis, isolation or parameter estimation. The subsequent model errors and unmodeled dynamics have somehow limited the application of the strategies. Therefore, this paper proposes a passive fault-tolerant individual pitch control scheme independent of the above process, and based on the scheme, a dual multivariable model-free adaptive control strategy with differential characteristic is constructed. The benchmark 5 MW wind turbine model provided by FAST is employed to evaluate the performance. The results show that, compared with the traditional individual pitch control strategy, the proposed scheme can achieve almost identical load control and even better power control under fault-free conditions. Once the fault occurs, the proposed scheme can quickly compensate for the faulty actuator dynamics, and finally achieve almost the same performance in power and load control as under the nominal conditions.

Robust Passive Fault Tolerant Control for Air Fuel Ratio Control of Internal Combustion Gasoline Engine for Sensor and Actuator Faults

This paper presents a novel Passive Fault Tolerant Control System (PFTCS) for Air Fuel Ratio (AFR) control system of the Internal Combustion (IC) gasoline engine to prevent its shutdown. A Proportional plus Integral (PI) controller with high feedback gain is implemented to control AFR by introducing a fuel throttle valve in the fuel line of the engine. The salient feature of the proposed controller is its less complex structure due to the absence of Analytical Redundancy (AR). Dual redundancy in the hardware is suggested for the sensors to prevent tripping in case of coincident faults in multiple sensors and for the actuator assembly to confiscate a single point of failure. The robustness of the proposed PFTCS is tested by introducing noise in the sensor measurements. MATLAB / Simulink environment simulation results demonstrate that the proposed PFTCS is robust to faults in normal as well as noisy conditions of the sensors without any degradation of AFR. The stability analysis of the proposed controller is performed by determining the poles of the closed-loop system. The reliability analysis of the proposed controller has been performed by calculating the probabilistic reliability function of the model. The comparison of the proposed model with the existing models has also been carried out to elaborate its effectiveness.

Application of metaheuristic algorithms in interval type-2 fractional order fuzzy TID controller for nonlinear level control process under actuator and system component faults*

PurposeThe two-tank level control system is one of the real-world's second-order system (SOS) widely used as the process control in industries. It is normally operated under the Proportional integral and derivative (PID) feedback control loop. The conventional PID controller performance degrades significantly in the existence of modeling uncertainty, faults and process disturbances. To overcome these limitations, the paper suggests an interval type-2 fuzzy logic based Tilt-Integral-Derivative Controller (IT2TID) which is modified structure of PID controller.Design/methodology/approachIn this paper, an optimization IT2TID controller design for the conical, noninteracting level control system is presented. Regarding to modern optimization context, the flower pollination algorithm (FPA), among the most coherent population-based metaheuristic optimization techniques is applied to search for the appropriate IT2FTID's and IT2FPID's parameters. The proposed FPA-based IT2FTID/IT2FPID design framework is considered as the constrained optimization problem. System responses obtained by the IT2FTID controller designed by the FPA will be differentiated with those acquired by the IT2FPID controller also designed by the FPA.FindingsAs the results, it was found that the IT2FTID can provide the very satisfactory tracking and regulating responses of the conical two-tank noninteracting level control system superior as compared to IT2FPID significantly under the actuator and system component faults. Additionally, statistical Z-test carried out for both the controllers and an effectiveness of the proposed IT2FTID controller is proven as compared to IT2FPID and existing passive fault tolerant controller in recent literature.Originality/valueApplication of new metaheuristic algorithm to optimize interval type-2 fractional order TID controller for nonlinear level control system with two type of faults. Also, proposed method will compare with other method and statistical analysis will be presented.

Hybrid Adaptive Fault-Tolerant Control for Compound Faults of Hypersonic Vehicle

This study investigates the hybrid fault-tolerant control (FTC) for hypersonic flight vehicles (HFVs) under the rudder structure fault (RSF) and rudder angle deviation fault (RADF). The nonlinear equations of the model are linearised by fuzzy logic, the external nonlinear disturbance is approximated by radial basis functions, which transforms the classical HFV into a linear system. In the case of only a RSF, the state feedback system can passively shield the fault using a compensation function and design a threshold to create conditions for RADF detection. During the RSF and RADF compound faults, the system with an adaptive observer implements angle deviation fault isolation/estimation and shields the structural fault. By using the estimation results, active-passive hybrid compensation completes passive FTC of the structural fault and active FTC of the angle deviation fault. The adaptive learning rates that mimic animal predatory behaviour increase the sensitivity to incipient deviation of RADF and improve compensation. Lyapunov method proves the stability and semi-physical simulation shows the control efficiency.