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This paper proposes a virtual sensor scheme designed to compensate for sensor fault effects in marine fuel engines. The proposed scheme design follows a distributed approach, where the marine fuel engine is decomposed in several subsystems. Then, for each subsystem we design a monitoring agent that can actively compensate for the effects of sensor faults occurring in the specific subsystem. This is realized using virtual sensors that can estimate the sensor fault in order to reconstruct the faulty measurements. Due to the Differential-Algebraic mathematical description of marine fuel engine dynamics, we design three types of virtual sensors; using adaptive observers, Set Inversion via Interval Analysis (SIVIA) and static models. Simulation results are used to illustrate the efficiency of the method.

peer-reviewed Fault-tolerant control system for marine robots, developed by researchers at Centre for Robotics & Intelligent Systems (CRIS), University of Limerick, utilises the hybrid method for control allocation, based on the integration of the pseudoinverse and the fixed-point iteration method. The algorithm is implemented as a two-step process. In the first step, the pseudoinverse solution is found, and the feasibility of the solution is examined analysing its components. If violation of actuator constraint(s) is detected, the fixed-point iteration method is activated in the second step. In this way, the hybrid method for control allocation can allocate the exact solution, optimal in the l2 sense, inside the entire attainable command set. This solution minimises a control energy cost function, the most suitable criteria for underwater applications. The performance of the thruster fault-tolerant control system has been validated during the research cruise CE19001, where the work-class ROV Étaín, deployed from support vessel Celtic Explorer via Tether Management System (TMS), successfully performed several complex subsea tasks with a faulty horizontal thruster. This paper describes the algorithm, provides geometric interpretation and presents the results from field trials.

International audience; Tilt rotor unmanned aerial vehicle (TRUAV) is a transformable aircraft with abilities of hovering and high-speed cruise. Its transition control is still a difficult point due to varying structure and dynamic behaviour. The main contribution of this paper is to put forward a transition control method based on backstepping for a quad-TRUAV, and fault tolerant control is researched to keep its cruise ability under rotor-tilt axle stuck fault. Explicit mode transition would be avoided by regarding rotor-tilt angle as a control input generated from decoupling with virtual control variables. Numerical results in transition procedure and facing rotor-tilt axle faults are provided to illustrate control effectiveness.

Comunicació presentada a SAFEPROCESS 2018. 10th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes (Warsaw, Poland, 29–31 August 2018) Wind turbines are prone to multiple different faults and input observability conditions are not always guaranteed for these faults. In such cases, it is not possible to build estimators which provide appropriate fault estimates for its further use in active FTC schemes such as fault tolerant MPC. Provided that these faults are generally non-simultaneous, we make use of this property for building banks of model-based estimators and statistical-based decision mechanisms that provide appropriate fault estimates for enhancing active FTC capabilities. We apply these strategies to a well-known wind turbine FDI and FTC benchmark and we show the effectiveness of the bank of estimators and decision mechanisms for estimating the faults occurring in the pitch system of a wind turbine.

The paper is devoted to the problem of fault accommodation in nonlinear dynamic systems related to constructing the control law which provides full decoupling with respect to fault effects. Existing conditions are formulated and calculating relations are given for the control law. The logic-dynamic approach is used to solve the problem whose features are consideration of the systems with non-smooth nonlinearities and the use of relatively simple linear methods which may be supported by existing programming systems, e.g. MatLab.

This paper presents an active fault tolerant control of a Remotely Operated Vehicle (ROV) propulsion system. An open frame ROV usually requires multi-thruster system to generate various motions. A general framework of active fault tolerant control contains the fault detection and diagnosis (FDD) subsystem and controller re-design subsystem. The FDD subsystem consists of fault detection, isolation and estimation while fault accommodation is chosen as the controller re-design method. In harsh operating environment, thrusters are liable to fault. Therefore, each thruster is monitored by a sensor module called thruster monitoring unit (TMU). As part of FDD subsystem, this module generates information regarding the status of thruster in form of armature voltage and current load feedback. In the case of thruster failure, it is possible to exploit the excessive number of available thruster by re-allocating the required control inputi.e. forces and moments acting on the vehicle. This re-allocation procedure is done by fault accommodation subsystem. A Takagi-Sugeno (T-S) fuzzy method is used to accommodate the thruster faults by penalizing the affected thruster and allowing others to continue the operation. An experimental result is presented by demonstrating the effect a blocked ducting and power supply malfunction. The fault accommodation using T-S fuzzy method is proved to be reliable, fast and efficient in handling and accommodating the thruster fault.

Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. This paper addresses the problem of integrated robust fault estimation (FE) and accommodation for discrete-time Takagi-Sugeno (T-S) fuzzy systems. First, a multiconstrained reduced-order FE observer (RFEO) is proposed to achieve FE for discrete-time T-S fuzzy models with actuator faults. Based on the RFEO, a new fault estimator is constructed. Then, using the information of online FE, a new approach for fault accommodation based on fuzzy-dynamic output feedback is designed to compensate for the effect of faults by stabilizing the closed-loop systems. Moreover, the RFEO and the dynamic output feedback fault-tolerant controller are designed separately, such that their design parameters can be calculated readily. Simulation results are presented to illustrate our contributions. Refereed/Peer-reviewed

This paper studies the problem of fault accommodation of time-varying delay systems using adaptive fault diagnosis observer. Based on the proposed fast adaptive fault estimation (FAFE) algorithm using only a measured output, a delay-dependent criteria is first established to reduce the conservatism of the design procedure, and the FAFE algorithm can enhance the performance of fault estimation. On the basis of fault estimation, the observer-based fault-tolerant tracking control is then designed to guarantee tracking performance of the closed-loop systems. Furthermore, comprehensive analysis is presented to discuss the calculation steps using linear matrix inequality technique. Finally, simulation results of a stirred tank reactor model are presented to illustrate the efficiency of the proposed techniques. Copyright © 2009 John Wiley & Sons, Ltd.

This paper studies the problem of fault estimation and accommodation for a class of nonlinear time-varying delay systems using adaptive fault diagnosis observer (AFDO). A novel fast adaptive fault estimation algorithm that does not need the derivative of the output vector is proposed to enhance the performance of fault estimation. Meanwhile, a delay-dependent criteria is obtained based on free weighting matrix method with the purpose of reducing the conservatism of the AFDO design. On the basis of fault estimation, an observer-based fault-tolerant controller is designed to guarantee the stability of the closed-loop system. In terms of matrix inequality, we derive sufficient conditions for the existence of the adaptive observer and fault-tolerant controller. Simulation results are presented to illustrate the efficiency of the proposed method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

The paper presents a robust fault diagnosis scheme for detecting and accommodating faults occurring in a class of nonlinear multi-input multi-output dynamical systems. Changes in the system dynamics due to a fault are modeled as nonlinear functions of the control input and state variables. The proposed fault accommodation scheme provides a way to augment the nominal controller such that the stability of the closed-loop system is retained in the presence of an unknown fault and of bounded disturbances. The stability of the robust fault accommodation scheme is rigorously established using Lyapunov redesign methods. " 33 717 722

In this paper a fault tolerant observer scheme is proposed for a wind turbine. The scheme provides estimates of the rotor, generator and wind speed which is tolerant towards faults in different relevant sensors in the wind turbine. The scheme is designed to and tested on a benchmark model for fault detection and isolation and fault tolerant control of wind turbines. These tests show the potential of the proposed scheme.

Faulty control surface actuator in a small Unmanned Aerial Vehicles (sUAV) could be overcome with a few techniques. Redundant actuators, analytical redundancy or combination of both are normally used as fault accommodation techniques. In this paper, the accommodation technique of faulty elevator actuator is presented. This technique uses a standby control surface as temporary control reallocation. Wind tunnel measurement facility is set up for the experimental validation and it is compared with FoilSim software. Flat plate airfoil which was used as horizontal stabilizer, is simulated using numerical model and it is validated using the wind tunnel test. Then, a flat airfoil is designed to be used as stabilator for the recovery of faulty elevator actuator. Results show the different deflection angle is needed when transferring from one control surface to another. From the analysis, the proposed method could be implemented without affecting the pitch stability during control surface transition. The alternate control surface accommodation technique proves to be promising for higher reliability sUAV in the case of a faulty on-board actuator.