This paper considers sliding mode allocation schemes for fault tolerant control. The schemes allow redistribution of the control signals to the remaining functioning actuators when a fault or failure occurs. The paper analyzes the schemes and determines conditions under which closed-loop stability is retained for a certain class of faults and failures. It is shown that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. The results obtained from implementing the controllers on the SIMONA research flight simulator, configured to represent a B747 aircraft, show good performance in both nominal and failure scenarios even in wind and gust conditions.

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This paper presents piloted flight simulator results associated with the EL-AL flight 1862 scenario using a model reference-based sliding mode control allocation scheme for fault tolerant control. The proposed controller design was carried out without any knowledge of the type of failure, and in the absence of any fault detection and isolation strategy. This is motivated by the fact that the flight crew were unaware of the loss of the right engines. For this reason, the control allocation scheme which is proposed uses (fixed) equal distribution of the control signals to all actuators (for both nominal situations and when a fault or failure occurs). The paper analyzes the scheme and determines the conditions under which closed-loop stability is retained. The results represent the successful real-time implementation of the proposed controller on the SIMONA motion flight simulator configured to represent a B747 aircraft. The evaluation results from the experienced pilots show that the proposed controller has the ability to position the aircraft for landing in both a nominal and the EL-AL failure scenario. It is also shown that actuator faults and failures which occured during the EL-AL incident can be handled directly without reconfiguring the controller.

A high fidelity aircraft simulation model, reconstructed using the Digital Flight Data Recorder (DFDR) of the 1992 Amsterdam Bijlmermeer aircraft accident (Flight 1862), has been used to evaluate a new Fault-Tolerant Flight Control Algorithm in an online piloted evaluation. This paper focuses on the piloted simulator evaluation results. Reconfiguring control is implemented by making use of Adaptive Nonlinear Dynamic Inversion (ANDI) for manual fly by wire control. After discussing the modular adaptive controller setup, the experiment is described for a piloted simulator evaluation of this innovative reconfigurable control algorithm applied to a damaged civil transport aircraft. The evaluation scenario, measurements and experimental design, as well as the real-time implementation are described. Finally, reconfiguration test results are shown for damaged aircraft models including component as well as structural failures. The evaluation shows that the FTFC algorithm is able to restore conventional control strategies after the aircraft configuration has changed dramatically due to these severe failures. The algorithm supports the pilot after a failure by lowering workload and allowing a safe return to the airport. For most failures, the handling qualities are shown to degrade less with a failure than the baseline classical control system does.

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This paper proposes a fault tolerant control scheme for linear parameter varying systems based on integral sliding modes and control allocation, and describes the implementation and evaluation of the controllers on a 6 degree-of-freedom research flight simulator called SIMONA. The fault tolerant control scheme is developed using a linear parameter varying approach to extend ideas previously developed for linear time invariant systems, in order to cover a wide range of operating conditions. The scheme benefits from the combination of the inherent robustness properties of integral sliding modes (to ensure sliding occurs throughout the simulation) and control allocation, which has the ability to redistribute control signals to all available actuators in the event of faults/failures. Index TermsSliding mode control, Fault tolerance, Aerospace simulation. I. INTRODUCTIONThe most important facet of Fault Tolerant Control (FTC) systems is their ability to maintain closed-loop stability, and ideally a measure of performance, in the face of faults or failures in actuators or sensors. The majority of the FTC methods that have appeared in the literature are based on linear time invariant (LTI) systems (see for example [1]). There are however notable exceptions: for example an observer based scheme for a specific class of input-output stable nonlinear systems is proposed in [2]; a passive FTC approach is proposed in [3] for a class of affine nonlinear systems considering actuator faults; and in [4], a FTC scheme for a specific class of nonlinear systems is proposed based on a sliding mode control allocation scheme incorporating a backstepping controller.Linear parameter varying (LPV) systems are a special class of finite dimensional linear systems, in which the entries of the state space matrices continuously depend on a time varying parameter vector which belongs to a bounded compact set. Using LPV techniques, the control law can be automatically 'scheduled' with the operating conditions and guaranteed performance can be proved over a wide operating envelope. FDI and FTC methods designed for LPV models have appeared in the literature. In [5], a synthesis method using LMIs is presented in order to guarantee closed-loop stability in the case of multiple actuator faults. In [6] an FDI scheme based on the extension of residual generation concepts for LTI systems was presented and tested on a model of a B747-100/200.Sliding mode control (SMC) is attractive from an FTC stand point, since actuator faults can be modelled as matched uncertainty, which is precisely the class of uncertainty to which sliding modes are robust [7]. However SMC cannot directly deal with total actuator failures because the complete loss of effectiveness in a channel destroys the regularity of the sliding mode, and an unique equivalent control signal can no longer be determined. To obviate this short-coming, in over actuated systems, a combination of SMC and control allocation (CA) has recently been explored [8]. In this context, CA can be viewed a...

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