Diederick Joosten

Online Aerodynamic Model Structure Selection and Parameter Estimation for Fault Tolerant Control

This paper describes a new recursive algorithm for the approximation of time varying nonlinear aerodynamic models by means of a joint adaptive selection of the model structure and parameter estimation. This procedure is called Adaptive Recursive Orthogonal Least Squares (AROLS), and is an extension and modification of the classical Recursive Orthogonal Least Squares (ROLS). This algorithm is considered to be particularly useful for indirect fault tolerant flight control, making use of model based adaptive control routines. After the failure, a completely new aerodynamic model can be elaborated recursively with respect to structure as well as parameter values. The performance of the identification algorithm is demonstrated on some simulation data sets.

Nonlinear Reconfiguring Flight Control Based on Online Physical Model Identification

This paper presents a study on fault tolerant flight control of a benchmark aircraft model. Reconfiguring control is implemented by making use of adaptive nonlinear dynamic inversion for manual and autopilot control. The weakness of classical nonlinear dynamic inversion, its sensitivity to modeling errors, is circumvented here by making use of a real-time identified physical model of the damaged aircraft. With help of the Boeing 747 benchmark simulation model, including the realistic component as well as the structural failure modes, it is possible to analyze the damage accommodation capabilities of the considered approach. In failure conditions, the damaged aircraft model is identified by the so-called two-step method in real time and this model is applied subsequently to the model-based adaptive nonlinear dynamic inversion routine in a modular structure, which allows flight control reconfigurations online. After discussing the modular adaptive controller setup, reconfiguration test results are shown for damaged aircraft models using a desktop computer as well as the moving base Simulation, Motion, and Navigation Research Flight Simulator of Delft University. These results indicate satisfactory failure handling capabilities of this fault tolerant control setup, for component as well as structural failures.

A Simulation Benchmark for Integrated Fault Tolerant Flight Control Evaluation

This paper presents a description of a large transp ort aircraft simulation benchmark that includes a suitable set of assessment criteria , for the integrated evaluation of fault tolerant flight control systems (FTFC). These syste ms consist of a combination of novel fault detection, isolation (FDI) and reconfigurable contr ol schemes. In 2004, a research group on Fault Tolerant Control, comprising a collaboration of nine European partners from industry, universities and research institutions, w as established within the framework of the Group for Aeronautical Research and Technology in Europe (GARTEUR) co-operation program. The aim of the research group, Flight Mechanics Action Group FM-AG(16), is to demonstrate the capability and viability of modern FTFC schemes when applied to a realistic, nonlinear design problem and to assess t heir capability to improve aircraft survivability. The test scenarios that are an integ ral part of the benchmark were selected to provide challenging assessment criteria to evaluate the effectiveness and potential of the FTFC methods being investigated. The application of fault reconstruction and modelling techniques based on (accident) flight data, as desc ribed in this paper, has resulted in high fidelity non-linear aircraft and fault models for t he design and evaluation of modern FTFC methods.

Fault-tolerant control using dynamic inversion and model-predictive control applied to an aerospace benchmark ⋆

This paper features the combination of model-based predictive control and dynamic inversion into a constrained and globally valid control method for fault-tolerant flight-control purposes. The fact that the approach is both constrained and model-based creates the possibility to incorporate additional constraints, or even a new model, in case of a failure. Both of these properties lead to the fault-tolerant qualities of the method. Efficient distribution of the desired control moves over the control effectors creates the possibility to separate the input allocation problem from the inversion loop when redundant actuators are available. An important part of this paper consists of the application of the proposed theory to an aerospace benchmark of high complexity. It is shown through an example that the theory is well-suited to the task, provided that fault-detection and isolation information is available continuously.

Piloted Simulator Evaluation Results of New Fault-Tolerant Flight Control Algorithm

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 recon- figurable 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.

Flight Control Reconfiguration based on a Modular Approac

Abstract This paper describes a reconfiguring flight control algorithm for damaged aircraft based upon a modular approach. This approach combines real time physical model identification with adaptive nonlinear dynamic inversion. The sensitivity of NDI to modeling errors is eliminated here by making use of a real time identified model of the aircraft. In failure situations, the damaged aircraft model is identified by the two step method and this updated model is supplied to the model-based adaptive NDI routine, which reconfigures for the failure in real time. Reconfiguration test results for damaged aircraft models indicate good failure handling capabilities of this fault tolerant control setup, for component as well as structural failures.

Computationally Efficient use of MPC and Dynamic Inversion for Reconfigurable Flight Control

†This paper features the combination of model-based predictive control and dynamic inversion into a constrained and globally valid control method for fault-tolerant flight-control purposes. The fact that the approach is both constrained and model-based creates the possibility to incorporate additional constraints, or even a new model, in case of a failure. Both of these properties lead to the fault-tolerant qualities of the method. Efficient distribution of the desired control moves over the control effectors creates the possibility to separate the input allocation problem from the inversion loop when redundant actuators are available. An important aspect that is considered here is the computational complexity of the presented methods. This complexity is reduced through application of an intelligent constraint mapping algorithm that allows for a strict separation of the applied model-predictive controller and the nonlinear dynamic inversion method. Furthermore, the complexity is reduced through application of a method that only uses the full set of available inputs, or actuators, when absolutely necessary, e.g. in a failure situation. Part of this paper consists of the application of the proposed theory to an aerospace benchmark of moderately high complexity. It is shown through an example that the theory is well-suited to the task, provided that fault-detection and isolation information is available continuously.

Assessment Criteria as Specifications for Reconfiguring Flight Control

To obtain a quantitative measure of predicted FTFC system performance in degraded modes, specifications need to be defined to assess proper functioning under realistic operational flight conditions. The goal of the benchmark specifications modelling, as described in this chapter, is to create a set of assessment criteria in order to evaluate the quality of the performance of fault detection and identification (FDI) and reconfigurable control algorithms. The lay-out of this chapter is as follows. First, the specifications modelling process is introduced by discussing the benchmark scenario. Subsequently, the general evaluation criteria will be considered by defining two classes of test manoeuvres. Thereafter, focus is placed on the test manoeuvres for FTFC qualification, which is the major topic of this chapter. After the discussion on how the assessment quantities of interest can be divided into two categories, four qualification test manoeuvres are discussed in depth. These include straight flight, right turn and localizer intercept, glideslope intercept and final approach with sidestep. Finally, a summary of the specified assessment quantities is given for the different FTFC qualification test manoeuvres. These criteria have also been published in Ref. [3].

MPC design for fault-tolerant flight control purposes based upon an existing output feedback controller

Abstract This paper investigates the qualities of a method for finding both a state-observer and the cost function associated with a model predictive controller, based upon an already existing output feedback controller. More specifically, an existing autopilot for a large transport aircraft is selected as the basis from which such a pair of an observer and a cost-function is to be determined. The goal of this exercise is to retain the properties of the existing controller, while adding the constraint handling capabilities of MPC. Consistent satisfaction of constraints is deemed an enabling quality in the application of MPC as a fault-tolerant controller for the aircraft benchmark under consideration.

RECOVER: A Benchmark for Integrated Fault Tolerant Flight Control Evaluation

Fault tolerant flight control (FTFC), or intelligent self-adaptive control, enables improved survivability and recovery from adverse flight conditions induced by faults, damage and associated upsets. This can be achieved by ’intelligent’ utilisation of the control authority of the remaining control effectors in all axes consisting of the control surfaces and engines or a combination of both. In this technique, control strategies are applied to restore vehicle stability, manoeuvrability and conventional piloting techniques for continued safe operation and a survivable landing of the aircraft.