Fault-tolerant Control System Research Articles

Flight Test Techniques - An Overview

Flight test techniques towards performance, handling qualities, stability and control are brought out. Hazardous flight conditions are covered. Instrumentation aspects are highlighted. Data reduction and some flight evaluation cases are addressed. Airframe structural performance under different conditions of flight test are explained. Fault tolerant flight control system testing is brought out. Features related to online development of restructurable and reconfigurable control laws are highlighted.

Fault-tolerant control strategy aiming at motion capability optimization for space manipulator with joint effectiveness partial loss failure

Aiming at the perturbation of motion capability and the deviation of end effector from its desired trajectory caused by joint effectiveness partial loss failure, a fault-tolerant control strategy considering motion capability optimization is proposed to ensure that the faulty space manipulator can carry on-orbit operation tasks. Firstly, the joint effectiveness partial loss failure model is established, and the kinematic and dynamic model of the faulty manipulator is established based on the failure model. The kinematic and dynamic coupling relationship of the faulty manipulator is also analyzed. Then based on sliding mode control, the fault-tolerant control strategy that ensures the end effector trajectory tracking and base orientation deflection attenuation is designed. Meanwhile, the motion capability optimization model is designed based on the redundancy characteristic of the manipulator and combined with the fault-tolerant control system. This combined system can realize end effector trajectory tracking, base orientation deflection attenuation, and motion capability optimization at the same time. Finally, simulation experiment is carried out to verify the proposed fault-tolerant control strategy for the faulty manipulator. The result shows that the proposed fault-tolerant control strategy can realize end effector trajectory tracking, base orientation deflection attenuation, and motion capability optimization with high control accuracy, high convergence rate, and significant motion capability optimization effect. For both joint velocity partial loss and joint torque partial loss failure, the duration of convergence is less than 0.5 s, the steady-state error is less than 1×10-4 m for end effector position and less than 1×10-5 degree for base orientation deflection, and the motion capability indexes have been raised by over 40%.

Fault-tolerant control strategy of six-phase permanent magnet synchronous motor based on deadbeat current prediction.

The fault-tolerant control after phase loss is crucial in the studies of the six-phase permanent magnet synchronous motor (PMSM), and the one phase loss is the most frequent phase loss fault. To improve the system instability caused by nonlinear and time-varying perturbations of inductance parameters in a double-Y phase shifted 30° six-phase PMSM, an improved deadbeat predictive current fault-tolerant control (DPC-FTC) method is proposed in this study. The transformation matrix after single-phase open-phase is first reduced and reconstructed, and the reduced-dimensional voltage equation is derived. Based on this equation, the deadbeat current predictive control is then used to predict the expected voltage using the current feedback value and the reference value, so as to shorten the response time and improve the overall control effect. The voltage equation after parameter perturbation is rewritten, and the current discrete transfer function under constant expected voltage before and after parameter perturbation is calculated. Afterwards, to further improve the low stability of fault-tolerant control after phase loss, which is caused by the inductance parameter perturbation of the control system, the weight coefficient is introduced in order to enhance the deadbeat predictive current control so that it splits and optimizes the direct-quadrature axis current. The stability of the system is then analyzed. By changing the weight coefficient, the fault-tolerant control system has a wider stable working range. Finally, the simulation model and experimental platform are completed. The results show that the improved DPC-FTC method improves the permissible inductor parameter uptake range by a factor of 1/β, reduces the current static difference by 32.05% and 46.02% when the inductor parameter is mismatched by a factor of 2, reduces the current oscillation and effectively reduces the sensitivity of system stability to inductor parameter uptake.

Wind Turbine Active Fault Tolerant Control Based on Backstepping Active Disturbance Rejection Control and a Neurofuzzy Detector

Wind energy conversion systems have become an important part of renewable energy history due to their accessibility and cost-effectiveness. Offshore wind farms are seen as the future of wind energy, but they can be very expensive to maintain if faults occur. To achieve a reliable and consistent performance, modern wind turbines require advanced fault detection and diagnosis methods. The current research introduces a proposed active fault-tolerant control (AFTC) system that uses backstepping active disturbance rejection theory (BADRC) and an adaptive neurofuzzy system (ANFIS) detector in combination with principal component analysis (PCA) to compensate for system disturbances and maintain performance even when a generator actuator fault occurs. The simulation outcomes demonstrate that the suggested method successfully addresses the actuator generator torque failure problem by isolating the faulty actuator, providing a reliable and robust solution to prevent further damage. The neurofuzzy detector demonstrates outstanding performance in detecting false data in torque, achieving a precision of 90.20% for real data and 100% for false data. With a recall of 100%, no false negatives were observed. The overall accuracy of 95.10% highlights the detector’s ability to reliably classify data as true or false. These findings underscore the robustness of the detector in detecting false data, ensuring the accuracy and reliability of the application presented. Overall, the study concludes that BADRC and ANFIS detection and isolation can improve the reliability of offshore wind farms and address the issue of actuator generator torque failure.

Novel barrier Lyapunov function-based backstepping fault tolerant control system for an ROV with thruster constraints

This paper proposes a novel Barrier Lyapunov Function (BLF)-based fault tolerant control system for a work-class Remotely-Operated Vehicle (ROV) with thruster saturation and rate limits. The proposed control system is composed of a fixed-time state and fault observer, and a novel BLF-based backstepping controller. The novel BLF-based controller is introduced to eliminate the sensitivity of conventional BLF-based algorithms to rate limitations of the thrusters. In addition, it helps to improve the performance during initial transients and provides faster response to fault and failures. The observer combines the dynamics of the ROV with the dynamics of the thruster system. This combination facilitates estimation of thruster faults and failures independently of the system uncertainties, so highly improved performance is expected compared to conventional extended-state observers. To account for thruster constraints and provide fault tolerance, control allocation is utilized. Stability analysis is performed for the observer and controller, and it is shown that the state estimation error is fixed-time convergent, the fault estimation unit is bounded-input bounded-output stable, and the controller is exponentially stable. Simulations are carried out and comparisons are made with several asymptotic and finite-time BLF-based control systems. The simulations confirm the superior performance of the proposed control system.

Saturation-tolerant prescribed function-based adaptive fault-tolerant tracking control for ACV with uncertainty and faults

This paper presents an adaptive fault-tolerant control system for Trajectory tracking of air-cushioned vehicles (ACVs) in the presence of actuator saturation, internal and external system perturbations. The proposed approach utilizes a state observer to estimate and compensate for the disturbances and saturation fault information present in the tracking system of the ACV. To achieve the desired performance, a new prescribed performance function (PPF) is introduced that is both global and saturated-tolerant. The PPF ensures that the error converges to a predetermined function in fixed time for any initial value, although it weakens the limits on the amount of overshoot. The combination of the observer and PPF with a backstepping fault-tolerant controller leads to improved transient and steady-state performance of the tracking control system for ACV. Simulation results demonstrate the effectiveness of the proposed approach.

Fault-tolerant control based on reinforcement learning and sliding event-triggered mechanism for a class of unknown discrete-time systems

This paper presents an adaptive fault-tolerant control (FTC) system based on reinforcement learning using an even-triggered mechanism. The even-triggered mechanism is established through a justifiable sliding surface and triggered function, without the need for any fault detection or observer. The learning laws are derived to ensure the convergence of internal signals and tracking error, and an actor–critic architecture is designed accordingly. To validate the proposed scheme, an experimental system is constructed and tested using five typical actuator faults. The results indicate a positive closed-loop performance and a reduction of approximately 25% in data transmission for both cases with and without faults.

Fault-Tolerant Control of Doubly Salient Electromagnetic Generator Based on Capacitor Split-Phase Bridge Converter Under Loss of Excitation

Doubly salient electromagnetic machine (DSEM) has the advantages of simple construction, easy power generation control and convenient fault de-excitation, making it a promising application in the aviation field. Aviation power generation system puts forward higher requirements for the reliability of generators. Despite the various studies on the fault-tolerant control of DSEM, there are few studies on fault-tolerant control of excitation fault in aviation power generation system. Therefore, the main purpose of this paper is to achieve fault-tolerant power generation (FTPG) system for doubly salient electromagnetic generator (DSEG) on the event of excitation fault and improve the fault tolerance ability of the system, while can improve output power and reduce copper loss of DSEG under loss of excitation. This paper analyses the basic principle of normal power generation about DSEG, establishes its equivalent circuit after excitation loss, and dissects the control strategy for the FTPG with loss of excitation based on a bridge converter. Besides, this paper also proposes a fault-tolerant control system and its control strategy based on a capacitor split-phase bridge (CSPB) converter for DSEG, with higher generated power as well as lower copper loss. Based on the above hypothesis, experiments are performed on a power generation system for 12/8 pole DSEG to verify the feasibility of the proposed method.

Технологии применения распределенных вычислений при построении перспективных сбое- и отказоустойчивых орбитальных группировок малых космических аппаратов

The paper examines issues of introducing the distributed computational technologies in constructing the fail-safe and fault-tolerant control systems for spacecraft constellations of various purposes. Various target objectives require various tools to achieve the task. Comparative analysis of the existing distributed computational technologies operating with the responsive application systems was performed including the spacecraft constellation control systems, to identify the most acceptable solutions. Principles of constructing the network-centric systems in controlling the spacecraft constellations were considered. Distributed computational technologies were analyzed not only from the point of view of solving the target problems by the spacecraft constellations, but also from the point of view of ensuring their reliability, as well as in organizing the spacecraft constellation control systems.

Fault tolerant control system for an ROV based on a novel integral sliding mode control and a state and fault observer in the presence of thruster limitations

This paper presents a novel fault tolerant control system for remotely operated vehicles in the presence of unknown system dynamics and unknown thruster faults and failures while accounting for magnitude and rate limits of the thrusters. The proposed control system consists of a novel integral sliding mode control (ISMC) and a new state and fault observer. The proposed ISMC utilizes a novel asymptotic sliding surface to enhance the performance of the control system during both initial transients and steady-state conditions. The observer takes thrusters system dynamics into account and provides estimation of faults and failures. Control allocation is utilized for fault accommodation and to separate the high-level control system and the low-level thruster controllers. Stability analyses are carried out and it is shown that the state observer is guaranteed to be fixed-time convergent while the fault observation error is input-to-state stable. It is also shown that the ISMC-based closed-loop control system is uniformly-ultimately bounded with practically fixed-time reaching phase. Simulations are carried out and comparisons are made with several fixed-time and finite-time control systems. The results outline the superior performance of the proposed control system in terms of positioning accuracy and fault tolerance during initial transients and steady-state conditions.

Multi-Layer Fault-Tolerant Protection Strategies for Hybrid Distribution Transformers Integrated Photovoltaic Systems

The hybrid distribution transformer integrated photovoltaic system (HDT-PV) is a promising solution for realizing the local consumption of distributed solar energy and solving the problems of the following power quality in the active distribution network. Due to the integration of power electronic converters and photovoltaic systems with low-frequency transformers, the fault situations of the HDT-PVs are more complicated and frequent than those of conventional distribution transformers. The lack of protection strategies for the HDT-PV, a new type of power equipment, greatly reduces its reliability and limits its potential for practical applications. To address this issue, the paper proposes multi-layer protection strategies for the HDT-PVs to remove the faulty part under different possible failure conditions. For each protection strategy, the corresponding fault-tolerant control system of the HDT-PV is designed to ensure the normal operation of other functions under different fault conditions. Finally, simulation and experimental results are provided to verify the effectiveness of the proposed multi-layer fault-tolerant protection strategies for the HDT-PVs.

Research on magnetic field and temperature field of multi-phase SPMSM under winding fault

In order to quickly and accurately calculate fault-tolerant capability of multi-phase surface-mount permanent magnet synchronous motor (SPMSM) at condition of asymmetrical fault, based on subdomain model, an analytical model for multi-phase SPMSM with asymmetric fault is proposed to calculate magnetic field distribution. Firstly, air-gap flux density, no-load back electromotive force (EMF) and electromagnetic torque are obtained accurately. Then, in order to improve the fault-tolerant capability of multi-phase SPMSM, with the minimum phase current as optimization objective, a fault-tolerant control system under the condition of single-phase winding disconnection is established. The performance of electromagnetic torque and torque ripple are used as evaluation indicators. Finally, taking a 12-phase SPMSM prototype with 44-poles 48-slots as an example, the effectiveness of proposed model is proved by 2D finite element model (FEM) and experiment test.

Nonlinear Fault-Tolerant Vibration Control for Partial Actuator Fault of a Flexible Arm

This paper presents a nonlinear fault-tolerant vibration control system for a flexible arm, considering partial actuator fault. A lightweight flexible arm with lower stiffness will inevitably cause vibration which will impair the performance of the high-precision control system. Therefore, an operator-based robust nonlinear vibration control system is integrated by a double-sided interactive controller actuated by the Shape Memory Alloy (SMA) actuators for the flexible arm. Furthermore, to improve the safety and reliability of the safety-critical application, fault-tolerant dynamics for partial actuator fault are considered as an essential part of the proposed control system. The experimental cases are set to the partial actuator as faulty conditions, and the proposed vibration control scheme has fault-tolerant dynamics which can still effectively stabilize the vibration displacement. The reconfigurable controller improves the fault-tolerant performance by shortening the vibration time and reducing the vibration displacement of the flexible arm. In addition, compared with a PD controller, the proposed nonlinear vibration control has better performance than the traditional controller. The experimental results show that the effectiveness of the proposed method is confirmed. That is, the safety and reliability of the proposed fault-tolerant vibration control are verified even if in the presence of an actuator fault.

Adaptive fuzzy fast terminal sliding mode control for inverted pendulum-cart system with actuator faults

In this work, the adaptive fuzzy fast terminal sliding mode control (AFFTSMC) is used to create a robust fault-tolerant control system for the care and swing-up control problem of the inverted pendulum-cart system is developed in the presence of actuator faults and external disturbances. The proposed controller has the benefit of the fast terminal sliding mode control (FTSMC) method to guarantee faults and uncertainties compensation, small tracking error, chattering phenomenon reduction, and fast transient response. To compensate for the uncertainties and actuator faults effects that can happen in practical tasks of an inverted pendulum-cart system, a new adaptive FTSMC method is proposed, where the prior knowledge of external perturbation and uncertainties is not required. In addition, the developed controller reduces the chattering phenomenon without disappearing the tracking precision and robustness property. Stability demonstration has been effectuated utilizing Lyapunov method. Practical results prove the efficiency of the suggested control algorithm.

Avoiding contingent incidents by quadrotors due to one or two propellers failure.

With the increasing impact of drones in our daily lives, safety issues have become a primary concern. In this study, a novel supervisor-based active fault-tolerant (FT) control system is presented for a rotary-wing quadrotor to maintain its pose in 3D space upon losing one or two propellers. Our approach allows the quadrotor to make controlled movements about a primary axis attached to the body-fixed frame. A multi-loop cascaded control architecture is designed to ensure robustness, stability, reference tracking, and safe landing. The altitude control is performed using a proportional-integral-derivative (PID) controller, whereas linear-quadratic-integral (LQI) and model-predictive-control (MPC) have been investigated for reduced attitude control and their performance is compared based on absolute and mean-squared error. The simulation results affirm that the quadrotor remains in a stable region, successfully performs the reference tracking, and ensures a safe landing while counteracting the effects of propeller(s) failures.

Design of hybrid fault-tolerant control system for air-fuel ratio control of internal combustion engines using artificial neural network and sliding mode control against sensor faults

This paper proposes a novel hybrid fault-tolerant control system (HFTCS) with dedicated non-linear controllers: artificial neural network (ANN) and sliding mode control (SMC) for active and passive parts, respectively. The proposed system can provide both desirable properties of stability to unexpected fast disturbances and post-fault optimal performance. In the active fault tolerant control system (AFTCS) part, the fault detection and isolation (FDI) unit is designed through the use of ANN for the estimation of faulty sensor values in the observer model. In the passive fault-tolerant system (PFTCS) part, the air-fuel ratio (AFR) controller is designed using a robust SMC that allows systems to manage faults in predefined limits without estimation. In the proposed system, SMC will form the passive part to react instantly to faults while ANN will optimize post-fault performance with active compensation. Moreover, Lyapunov stability analysis was also performed to make sure that the system remains stable in both normal and faulty conditions. The simulation results in the Matlab/Simulink environment show that the designed controller is robust to faults in normal and noisy measurements of the sensors. A comparison with the existing works also demonstrates the superior performance of the proposed hybrid algorithm.

Luenberger Observer-Based Speed Sensor Fault Detection: real time implementation to DC Motors

Fault Tolerant Control Systems (FTCS) have emerged as a critical area of study for enhancing the safety, reliability, and efficiency of modern control systems. The FTCS technique might be active or passive control in general. In this paper, the active control branch's Fault Detection and Diagnosis (FDD) is used to detect faults in DC motor speed sensors. FDD methodologies can be divided into two types based on the process and the type of data available: model-based methods and data-based methods. The proposed method here investigates the use of the Luenberger observer technique, which is part of the model-based approach. The selected method was implemented and experimentally evaluated. This observer is dependent on the residual signal, which serves as a fault indicator in the overall system and represents the difference between the measured and estimated speed signals from the plant. Due to the increasing demand for these motors, particularly in electro-mechanical applications such as robotics, elevators, and electric-driven railways, a DC motor was chosen as a benchmark to test the proposed method. The output speed of the motor was subjected to four sensor faults: sensor fault, abrupt fault, intermittent fault, and incipient fault. The effectiveness of the suggested approach is demonstrated using MATLAB simulations, and the results show that faults are detected as anticipated with a high-performing response. Therefore, the proposed method was also implemented experimentally in real time and the obtained results showed a close match with those from simulation, thus proving the accuracy and reliability of the proposed methodology for fault detection in the DC motor speed sensor.

Fault Tolerant Control of Drone Interceptors Using Command Filtered Backstepping and Fault Weighting Dynamic Control Allocation

This paper proposes a fault tolerant control strategy for drone interceptors with fixed wings and reaction jets subject to actuator faults. The drone interceptors have both continuous and discrete actuators, which pose a challenge to the control system design. The proposed fault tolerant control system consists of two parts, a nonlinear virtual control law and a dynamic control allocator. To deal with system uncertainty and quantization error, a virtual control law with a parameter update law is designed by command filtered backstepping. Then, a fault weighting dynamic control allocation algorithm is developed to distribute the virtual control signal to the actuators on the drone interceptor. When an actuator fault occurs, the proposed fault weighting dynamic control allocation scheme can redistribute the control signals to the remaining actuators. The effectiveness of the proposed algorithm is confirmed by numerical simulation.

Adaptive reinforcement learning fault-tolerant control for AUVs With thruster faults based on the integral extended state observer

In this paper, a reinforcement learning (RL) fault-tolerant control (FTC) method is proposed for trajectory tracking of autonomous underwater vehicles (AUVs) with thruster faults. To deal with the thruster fault, unknown disturbance and model uncertainty, a new integral extended state observer (IESO) for fault diagnosis observation is proposed, which uses a conventional ESO to estimate the total system uncertainty, and introduces an integral mechanism to mitigate the effect of estimation error further. Thus, the problem that the estimation error caused by the traditional ESO leads to the decline of the fault-tolerant capability of the FTC system is solved. Then, to solve the problem of integral saturation due to the introduction of the integral term, the integral term is limited after the thruster fault of the AUV. Furthermore, based on the actor–critic structure of RL, a PD-like feedback controller is designed to realize the FTC of AUV in the face of thruster fault by using the total uncertainty of the IESO scheme. And the input saturation of the thruster is considered, and an auxiliary variable system is used to handle the control truncation between saturated and unsaturated inputs. Based on the Lyapunov method, the stability of the closed-loop system is analyzed and proved. Finally, the proposed method is verified to have good fault tolerance and robustness by simulation and underwater experiments.

Multirotor Motor Failure Detection with Piezo Sensor

Failure detection of Unmanned Aerial Vehicle (UAV) motors and propulsion systems is the most important step in the implementation of active fault-tolerant control systems. This will increase the reliability of unmanned systems and increase the level of safety, especially in civil and commercial applications. The following paper presents a method of motor failure detection in the multirotor UAV using piezo bars. The results of a real flight, in which the failure of the propulsion system caused the crash of a hybrid VTOL UAV, were presented and analyzed. The conclusions drawn from this flight led to the development of a lightweight, simple and reliable sensor that can detect a failure of the UAV propulsion system. The article presents the outcomes of laboratory tests concerning measurements made with a piezo sensor. An extensive analysis of the obtained results of vibrations recorded on a flying platform arm with a propulsion system is presented, and a methodology for using this type of data to detect failures is proposed. The article presents the possibility of using a piezoelectric sensor to record vibrations on the basis of which it is possible to detect a failure of the UAV propulsion system.