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.
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.
A set of experiments has been conducted to investigate the relative effect of translational and rotational motion cues on pilot performance. Two helicopter yaw control tasks were performed on the SIMONA Research Simulator; a yaw capture task, and a target tracking task with simulated turbulence. The yaw capture task was a repetition of a task performed previously by Schroeder and Grant at two different simulator facilities. Shaping filters and added delays were used to match simulator characteristics with the previous experiments. In contrast to Schroeder and Grant's conclusions, results from the current study show more equal contributions of yaw and sway motion on performance and subjective simulator motion fidelity.Analyses of the different vestibular cues using multi-loop pilot models, estimated from measurement data from the target tracking task, also indicate comparable utilization of the yaw and sway motion cues.
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