Fault-tolerant Control Approach Research Articles

Distributed Adaptive Fault-Tolerant Control for Spacecraft Formation With Communication Delays

This paper investigates distributed adaptive fault-tolerant control schemes for spacecraft formation subject to external disturbances, model uncertainties and communication delays. Two novel adaptive fault-tolerant control approaches are presented based on directed communication interaction. The developed adaptive laws are used to estimate the actuator effectiveness, the spacecraft masses and the upper bound on external disturbances. Then, an adaptive fault-tolerant control algorithm with time-varying communication delays is proposed. In particular, the conditions on the controller parameters and the communication delays necessary to assure the asymptotic stability of the closed-loop system are given. Finally, numerical simulations are presented to validate the effectiveness of the two proposed fault-tolerant control schemes for the spacecraft formation system.

Event-Triggered Robust Adaptive Sliding Mode Fault-Tolerant Control For Nonlinear Systems

In this article, a novel two-channel event-triggered adaptive fault-tolerant control approach is designed to handle the degree freedom nonlinear system with disturbances. The main purpose of this article is to maintain the output tracking ability while reducing the transmission burden. The objective is realized by designing a novel adaptive sliding mode controller integrated with the event trigger mechanism. Concretely, the state, actuator fault, and lumped disturbance information are obtained by designing a composite observer, in which the disturbance upper bound is not needed. Then, the obtained information is utilized to design the controller. In the proposed method, the lumped disturbance and nonlinear estimated values are contained in the sliding mode manifold to enhance the robustness. Additionally, an adaptive parameter is also integrated into the controller to compensate for the disturbance. Furthermore, a specific event-triggered controller is proposed to keep the tracking ability and to reduce the transmission load of the fault system. The no Zeno phenomenon performance is analyzed and, finally, the applications to a suspension system and a two-tank system are given to show the fault tolerance ability of the proposed method.

Integrated fault tolerant attitude control approach for satellite attitude system with sensor faults

SummaryIn this study, a novel integrated fault tolerant control (FTC) strategy is proposed for a rigid satellite attitude systems under the case of external disturbance, Lipschitz nonlinearity, and sensor faults. Different from the traditional adaptive fault estimation method, an augmented fault estimation observer is designed for the considered faulty satellite attitude system, which could be used for estimating both system state and sensor fault. A virtual observer is firstly introduced, and then, a real observer is derived as a result of the unmeasurable information to be used for the design of the virtual observer. On this basis, an integrated FTC approach is developed for the considered faulty satellite attitude system by combining backstepping control and fractional order nonsingular terminal sliding mode control techniques, such that the closed‐loop system not only has good robustness to external disturbance but also has better fault tolerance capability to unknown sensor fault. Finally, a simulation example is provided to demonstrate the feasibility and advantage of the proposed FTC scheme.

A Novel Fault-Tolerant Control Method for Interleaved DC–DC Converters Under Switch Fault Condition

This article proposes an adaptive democratic current sharing control scheme for the interleaved dc–dc converters under faulty conditions. The proposed fault-tolerant control approach can achieve the desired output-voltage generation and equal current sharing among the remaining healthy modules as more and more modules fail. The main idea is to adaptively change the reference currents and the inner loop current regulator gains once the fault is detected in the modules. The proposed control scheme is compared to the democratic current sharing control scheme under the fault condition. The results show that it achieves improved output regulation and accurate current sharing among the modules. The presented fault-tolerant control method has been analyzed, tested, and validated for the interleaved boost converter.

Open-Phase Fault Modeling and Optimized Fault-Tolerant Control of Dual Three-Phase Permanent Magnet Synchronous Machines

This paper investigates open-phase fault modeling and fault-tolerant control (FTC) of dual three-phase permanent magnet synchronous machines (DT-PMSMs). A comprehensive fault model that considers both the permanent magnet torque and reluctance torque under the open-phase fault is proposed first. This model shows that under open-phase fault the average torque of DT-PMSM will decrease, while torque ripple will increase significantly. Then, a novel optimized FTC approach is developed based on the proposed model, in which genetic algorithm (GA) is applied to optimize the stator currents to maximize the average torque and minimize the torque ripple under open-phase fault. The proposed fault model and GA-based FTC are applicable to both surface-mounted and interior DT-PMSMs. However, existing approaches neglecting the reluctance torque are only applicable to surfaced-mounted DT-PMSMs. Moreover, the proposed approach is simple in implementation as it employs the original control structure and it is capable of smooth switching between the healthy operation and FTC without inducing noticeable torque pulses. The proposed approach is demonstrated with design examples, compared with existing one and validated with experiments on a laboratory interior DT-PMSM.

Sensor Fault Tolerant Control for Aircraft Engines Using Sliding Mode Observer

This paper investigated the problem of fault estimation and fault-tolerant control (FTC) against sensor faults for aircraft engines. By applying a second order sliding mode observer (SOSMO) to the engine on-board model, estimations of the system states and sensor faults could be obtained simultaneously, and the result of state estimation was unaffected when using the reduced-order sliding mode system. This result gave rise to the idea to use the estimated states instead of physical sensor signal in the engine close-loop feedback control. Unlike those using passive FTC concepts, the tradeoff between control performance and robustness was inherently unnecessary. Meanwhile, compared to active FTC approaches, because any classical state/output feedback method can be directly applied to the proposed scheme without any controller reconfiguration, extra undesired dynamic responses caused by parameter reconfiguring were avoided. In this paper, the proposed FTC scheme was tested on the nonlinear model of a civil aircraft turbofan engine, and numerical simulation results showed satisfactory sensor FTC performance.

A Direct Redundancy Approach to Fault-Tolerant Control of BLDC Motor With a Damaged Hall-Effect Sensor

Often for a closed-loop operation of a brushless direct current (BLDC) motor, Hall-effect sensors are used and recently there have been a number of discussions on Fault-Tolerant Control (FTC) of the BLDC motor for a defective Hall-effect sensor. However, so far, direct redundancy based approach for FTC of BLDC motor for a position sensor fault is not presented. This paper contributes a direct redundancy based method by utilizing redundant Hall-effect sensors for FTC of a BLDC motor. Redundant Hall-effect sensors generate additional transitions resulting in faster fault detection. To verify the proposed idea, MATLAB/Simulink model is developed, and the simulation results are presented by programing a MATLAB function block acting as a fault-tolerant controller. Furthermore, the algorithm is implemented into the MicroLabBox for experimental validation, and the results are discussed.

Fault-tolerant control of Y-connected three-phase induction motor drives without speed measurement

Fault-Tolerant Control (FTC) in adjustable speed drives under open-circuit faults has been broadly investigated in the literature. Nevertheless, studies in this area have been normally focused on sensored machine drives. This research focuses on the FTC approach for Y-connected Three-Phase Induction Motor (TPIM) drives without speed measurement. An Extended Kalman Filter (EKF) and a Rotor Field Oriented Control (RFOC) system are developed in order to control sensorless speed controlled Y-connected TPIM during both healthy and Single Phase Open-Circuit Fault (SPOCF) conditions. Unlike the conventional sensorless control system, the proposed drive system can be used for the sensorless speed controlled Y-connected TPIM during both normal and SPOCF conditions. The performances of the proposed FTC scheme are implemented on a DSP/TMS320F28335 controller board for a 0.75 kW Y-connected TPIM drive system. Different experimental results are shown to verify the effectiveness and possibility of the introduced technique.

Command filter-based fuzzy adaptive nonlinear sensor-fault tolerant control for a quadrotor unmanned aerial vehicle

In this paper, a novel asymptotic fuzzy adaptive nonlinear fault tolerant control (FTC) scheme is presented for the under-actuated dynamics of a quadrotor unmanned aerial vehicle (UAV) subject to diverse sensor faults. The proposed FTC approach can deal with both additive sensor faults (bias, drift, loss of accuracy) and multiplicative sensor fault (loss of effectiveness). The overall dynamics is separated into position loop and attitude loop for FTC controllers design. Combining uncertain parameters and external disturbances, the four types of faults occurring in velocity sensors and Euler angle rate sensors are transformed equivalently into the unknown nonlinear function vectors and uncertain control gains. Fuzzy logic systems are used to approximate the lumped nonlinear functions, and adaptive parameters are estimated online. Nussbaum technique is introduced to deal with the unknown control gains. For both control loops, FTC controllers are designed via command filter-based backstepping approach, in which sliding mode control is introduced to establish asymptotic stability. All tracking error signals of the closed-loop control system are proved to converge to zero asymptotically. Finally, simulation comparisons with other methods demonstrate the effectiveness of the proposed FTC approach for quadrotor UAV with sensor faults.

Integrated Fault-Tolerant Stabilization Control for Satellite Attitude Systems with Actuator and Sensor Faults

In this paper, the problem of integrated fault-tolerant stabilization control is studied for the attitude systems of a rigid satellite with both actuator and sensor faults. Firstly, a virtual observer is designed for the faulty attitude systems of rigid satellite in order to estimate the unknown actuator and sensor faults. Because the virtual observer includes unmeasurable information of the attitude systems, the real observer is then presented. On this basis, an integral sliding-mode fault-tolerant stabilization control approach is proposed by using the estimated fault information, and it not only suppresses the disturbance with a disturbance attenuation level $$\gamma $$ , but also eliminates the effects of actuator and sensor faults. Finally, the effectiveness of the proposed fault-tolerant stabilization scheme is demonstrated in the attitude systems of a rigid satellite subject to the time-varying actuator and sensor faults.

Fault-Tolerant Consensus Tracking Control for Linear Multiagent Systems Under Switching Directed Network

In this paper, for linear leader-follower networks with multiple heterogeneous actuator faults, including partial loss of effectiveness fault and actuator bias fault, a cooperative fault-tolerant control (CFTC) approach is developed. Assume that the interaction network topology among all nodes is a switching directed graph. To address the difficulty of designing the distributed compensation control laws under the time-varying asymmetrical network structure, a novel distributed-reference-observer-based fault-tolerant tracking control approach is established, under which the global tracking errors are proved to be asymptotically convergent in the presence of actuator failures. First, by constructing a group of distributed reference observers based on neighborhood state information, all followers can estimate the leader's state trajectories directly. Second, a decentralized adaptive fault-tolerant tracking controller via local estimation is designed to achieve the global synchronization. Furthermore, the reliable coordination problem under switching directed topology with intermittent communications is solved by utilizing the presented CFTC approach. Finally, the effectiveness of the proposed coordination control protocol is illustrated by its applications to a networked aircraft system.

High efficiency fault-detection and fault-tolerant control approach in Tennessee Eastman process via fuzzy-based neural network representation

We looked at the background of fault-detection and fault-tolerant control algorithms to propose a new high efficiency one with a focus on Tennessee Eastman process through fuzzy-based neural network representation. Due to the fact that the open-loop system may not be stabilized, an advanced control strategy to generate proper control signals needs to be designed. At first, to detect and identify the fault, data preprocessing theories have been considered. Based upon the matter disclosed, to provide a reliable decision-maker block, fusion classifier idea has been realized. For this one, raw data, time, and frequency characteristics are divided into various classification tools and finally the obtained knowledge combination regarding each one of them is adopted. It should be noted that the proposed implementation tools are taken into real consideration as the fuzzy-based neural network representation. Subsequently, the fault-tolerant control approach based on local controller regulation in case of each fault occurrence has been researched, which the investigated outcomes emphasize the effectiveness of the approach proposed here.

Global Fault-Tolerant Control of Underactuated Aerial Vehicles with Redundant Actuators

In this paper, we consider the fault-tolerant control problem for aerial vehicles with redundant actuators. The redundant actuator brings difficulty in fault identification and isolation. Active fault-tolerant control is adopted in this paper as it can detect actuator fault. The entire proposed fault-tolerant control algorithm contains a baseline controller, the fault detection and isolation scheme, and the controller reconstruction module. A robust parameter identification method is designed to identify the torque and thrust generated by the actuators. The feasibility of isolating the fault for the redundant actuators is analyzed through mathematical proof. Through the analysis, the practical fault isolation algorithm is also proposed. Two typical aerial vehicles with redundant actuators, an eight-rotor aircraft and a hexa-rotor aircraft, are adopted in numerical simulations to verify the effectiveness of the proposed fault-tolerant control approach.

Distributed adaptive fault-tolerant control approach to cooperative output regulation for linear multi-agent systems

In this paper, the cooperative output regulation problem for linear multi-agent systems with actuator faults is considered. It is assumed that the actuator faults are outage faults and loss-of-effectiveness faults. First, a distributed finite-time observer is designed to estimate the state of the exosystem. Based on the state of the finite-time observer, a distributed adaptive fault-tolerant controller is designed. Then, it is shown that the cooperative output regulation problem can be solved with the proposed fault-tolerant controller. Compared with the existing cooperative output regulation results, a novel lemma is introduced to guarantee the solvability of the regulator equations under actuator faults, and the developed controller is effective to compensate the actuator faults. Finally, a simulation example is presented to show the validity of the proposed method.

Robust Adaptive Sliding Mode Fault Tolerant Control for Nonlinear System with Actuator Fault and External Disturbance

In this paper, an adaptive sliding mode fault tolerant control (ASMFTC) approach is proposed for a class of nonlinear systems with actuator fault, uncertainty, and external disturbance. Specifically, first, a novel observer is proposed to estimate the state, actuator fault, and external disturbance. Then, by utilising the observed information, a novel output sliding mode observer is constructed. In the control method, an adaptive law and two compensators are designed to attenuate the unknown estimation errors, actuator fault, and disturbance. Furthermore, the reaching ability of the sliding motion is analysed and the H-infinite performance is introduced to ensure the robustness of the system. Finally, a flexible single joint manipulator system and a two-cart system are used to verify the effectiveness of the proposed method.

Neural Adaptive Fault Tolerant Control of Nonlinear Fractional Order Systems Via Terminal Sliding Mode Approach

This article proposes an adaptive neural output tracking control scheme for a class of nonlinear fractional order (FO) systems in the presence of unknown actuator faults. By means of backstepping terminal sliding mode (SM) control technique, an adaptive fractional state-feedback control law is extracted to achieve finite time stability along with output tracking for an uncertain faulty FO system. The unknown nonlinear terms are approximated by radial-basis function neural network (RBFNN) with unknown approximation error upper bound. Using convergence in finite time and fractional Lyapunov stability theorems, the finite time stability and tracking achievement are proved. Finally, the proposed fault tolerant control (FTC) approach is validated with numerical simulations on two fractional models including fractional Genesio–Tesi and fractional Duffing's oscillator systems.

Adaptive NFTSM-Based Fault Tolerant Control for a Class of Nonlinear System With Actuator Fault and Saturation

In this paper, an adaptive fault-tolerant control (FTC) strategy is proposed for a class of nonlinear systems in the presence of actuator fault, actuator saturation, and unknown external disturbance. The mathematical model of a second-order nonlinear system with actuator fault is first given, and a fault estimation observer is designed to estimate the occurred time-varying actuator fault. On this basis, the adaptive FTC strategy is proposed using both nonsingular fast terminal sliding mode (NFTSM) and radial basis function neural networks (RBFNNs) techniques to compensate for the negative effects caused by time-varying actuator fault and external disturbance. Another adaptive FTC scheme is further presented under actuator saturation case, and the Lyapunov stability analysis demonstrates that the designed FTC approach could guarantee that the trajectory of sliding mode dynamics could converge to a small neighborhood of the origin within a finite time. Compared with some existing results, the FTC approach proposed in this paper has better fault acceptability. Finally, the proposed adaptive FTC approach is applied to the attitude control of rigid spacecraft, and the simulation results illustrate the advantages of the designed control scheme.

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

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

Finite Time Fault Tolerant Control Design for UAV Attitude Control Systems with Actuator Fault and Actuator Saturation

This paper presents a novel fault tolerant control (FTC) strategy for an unmanned aerial vehicle (UAV) subject to multiple constraints of actuator fault, actuator saturation and external disturbance. First, a radial basis function neural network (RBFNN)-based fault estimation observer is developed to obtain the accurate value of actuator fault. Second, an attitude stabilization FTC approach is established with combining the non-singular fast terminal sliding mode (NFTSM) technology, which could tolerate the estimated loss of effectiveness fault. Third, it is discussed asymptotically stability and stabilization of UAV attitude systems in finite time by Lyapunov method and the improved FTC scheme. Finally, the simulation is carried out to verify the fault tolerant capability of the designed algorithm.

Adaptive Control Allocation with Communication Delay for In-Wheel Propulsion Electric Vehicles

In this paper, an integrated, fault-tolerant control approach for yaw stability of ground vehicles is outlined in the presence of actuator and sensor network delay. In order to simultaneously control all actuators in the vehicle, an adaptive control allocation method is used. The proposed control scheme consists of a high level controller that creates a virtual control input vector and a low level control allocation that distributes the virtual control effort among redundant actuators. Virtual control input consists of desired traction force, desired yaw moment and required lateral force correction to ensure stability while following a given reference. Based on this virtual control input vector, the allocation module determines front steering angle correction, rear steering angle, traction forces at each wheel. Presented control structure is simulated by using a 10 Degree of freedom vehicle model. Results show that the proposed approach can follow the references despite the loss of actuator effectiveness in the driving cycle with the presence of delay in the communication system while the system with no adaptive allocation fails to stay on course.