Comparative Analysis of Different Classes of On-line State Estimators for Aerodynamics Angles and True Airspeed Sensors for Applications to the Sensor Failure Problem

Throughout aviation history, there have been numerous incidents due to sensor failure that have caused a range of issues from loss of control of the aircraft to crashes resulting in loss of human life. Although there are many hardware-based solutions to this problem, the threat of control hardware failure still exists. This work investigates the efficacy of implementing neural networks (NN) and Kalman filters (KF) to solve the accommodation portion of the sensor failure detection, identification, and accommodation (SFDIA) problem through on-line real-time estimation of specific aircraft dynamic parameters. The implementation of on-line estimation architectures into the aircraft flight control system provides multiple advantages such as cost effectiveness and drastic decrease in weight. The multilayer perceptron (MLP) NN, extended minimal resource allocation (neural) network (EMRAN), extended KF (EKF), and unscented KF (UKF) have been evaluated in this effort for the purpose of providing analytical redundancy (AR) for estimating the parameter of the ‘failed’ sensor in lieu of physical redundancy. Each NN-based and KF-based estimator was compared using preset criteria including estimation accuracy, time to perform, and complexity of the model. The overall results have shown that the NN-based sensor failure accommodation (SFA) schemes outperform the KF-based SFA schemes with no undetected faults nor false alarms and significantly smaller estimation errors. More specifically, the EMRAN-based neural estimator has the best performance of all four schemes followed by the MLP NN, UKF, and EKF, respectively. This research shows the great potential of analytical redundancy-based approaches as opposed to physical or hardware redundancy to improved aviation safety for preventing future crashes due to sensor failures

Design and simulation of advanced fault tolerant flight control schemes

This research effort describes the design and simulation of a distributed Neural Network (NN) based fault tolerant flight control scheme and the interface of the scheme within a simulation/visualization environment. The goal of the fault tolerant flight control scheme is to recover an aircraft from failures to its sensors or actuators. A commercially available simulation package, Aviator Visual Design Simulator (AVDS), was used for the purpose of simulation and visualization of the aircraft dynamics and the performance of the control schemes.;For the purpose of the sensor failure detection, identification and accommodation (SFDIA) task, it is assumed that the pitch, roll and yaw rate gyros onboard are without physical redundancy. The task is accomplished through the use of a Main Neural Network (MNN) and a set of three De-Centralized Neural Networks (DNNs), providing analytical redundancy for the pitch, roll and yaw gyros. The purpose of the MNN is to detect a sensor failure while the purpose of the DNNs is to identify the failed sensor and then to provide failure accommodation. The actuator failure detection, identification and accommodation (AFDIA) scheme also features the MNN, for detection of actuator failures, along with three Neural Network Controllers (NNCs) for providing the compensating control surface deflections to neutralize the failure induced pitching, rolling and yawing moments. All NNs continue to train on-line, in addition to an offline trained baseline network structure, using the Extended Back-Propagation Algorithm (EBPA), with the flight data provided by the AVDS simulation package.;The above mentioned adaptive flight control schemes have been traditionally implemented sequentially on a single computer. This research addresses the implementation of these fault tolerant flight control schemes on parallel and distributed computer architectures, using Berkeley Software Distribution (BSD) sockets and Message Passing Interface (MPI) for inter-process communication

2020 Student Symposium Research and Creative Activity Book of Abstracts

The UMaine Student Symposium (UMSS) is an annual event that celebrates undergraduate and graduate student research and creative work. Students from a variety of disciplines present their achievements with video presentations. It’s the ideal occasion for the community to see how UMaine students’ work impacts locally – and beyond. The 2020 Student Symposium Research and Creative Activity Book of Abstracts includes a complete list of student presenters as well as abstracts related to their works

An SFDI Observer–Based Scheme for a General Aviation Aircraft

The problem of detecting and isolating sensor faults (sensor fault detection and isolation-SFDI) on a general aviation aircraft, in the presence of external disturbances, is considered. The proposed approach consists of an extended Kalman observer applied to an augmented aircraft plant, where some integrators are added to the output variables subject to faults. The output of the integrators should be ideally zero in the absence of model uncertainties, external disturbances and sensor faults. A threshold-based decision making system is adopted where the residuals are weighted with gains coming from the solution to an optimization problem. The proposed nonlinear observer was tested both numerically on a large database of simulations in the presence of disturbances and model uncertainties and on input-output data recorded during real flights. In this case, the possibility of successfully applying the proposed technique to detect and isolate faults on inertial and air data sensors, modelled as step or ramp signals artificially added to the real measurements, is shown

An SFDI observer-based scheme for a general aviation aircraft

The problem of detecting and isolating sensor faults (sensor fault detection and isolation - SFDI) on a general aviation aircraft, in the presence of external disturbances, is considered. The proposed approach consists of an extended Kalman observer applied to an augmented aircraft plant, where some integrators are added to the output variables subject to faults. The output of the integrators should be ideally zero in the absence of model uncertainties, external disturbances and sensor faults. A threshold-based decision making system is adopted where the residuals are weighted with gains coming from the solution to an optimization problem. The proposed nonlinear observer was tested both numerically on a large database of simulations in the presence of disturbances and model uncertainties and on input-output data recorded during real flights. In this case, the possibility of successfully applying the proposed technique to detect and isolate faults on inertial and air data sensors, modelled as step or ramp signals artificially added to the real measurements, is shown

An SFDI observer-based scheme for a general aviation aircraft

In this paper the problem of detecting and isolating sensor faults on a general aviation aircraft, in the presence of external disturbances, is considered. The proposed approach consists of an extended Kalman observer applied to an augmented aircraft plant, where some integrators are added to the output variables subject to faults. The output of the integrators should be ideally zero in the absence of model uncertainties, external disturbances and sensor faults. A threshold based decision making system is adopted where the residuals are weighted with gains coming from the solution of an optimization problem. The proposed nonlinear observer has been tested both numerically on a large database of simulations in the presence of disturbances and model uncertainties and on input-output data recorded during real flights. In this case, the possibility of successfully applying the proposed technique to detect and isolate faults on inertial and air data sensors, modelled as step or ramp signals artificially added to the real measurements, is shown. © 2013 IEEE

Rotordynamic Instability Problems in High-Performance Turbomachinery, 1990

The present workshop continues to report field experience and experimental results, and it expands the use of computational and control techniques with the integration of damper, bearing, and eccentric seal operation results. The intent of the workshop was to provide a continuing impetus for an understanding and resolution of these problems

The African Union and the Development of African International Criminal Law

Die vorliegende Arbeit steht im Kontext der Regionalisierung im Internationalen Strafrecht. Sie untersucht die Faktoren, die der entsprechenden Entwicklung des afrikanischen internationalen Strafrechts unter der Ägide der Afrikanischen Union (AU) zugrunde liegen und beleuchtet die Inhalte dieser sich entwickelnden Disziplin. Primäres Ziel der Arbeit ist es, die theoretischen und praktischen Grundlagen für die Entwicklung eines tragfähigen Systems afrikanischer Strafjustiz zu untersuchen, das in der Lage sein soll, mit Verbrechen gegen den Frieden und die Sicherheit in Afrika umzugehen, die die öffentliche Ordnung des Kontinents bedrohen. Im Weiteren entwickelt die Arbeit das Verhältnis des regionalen, afrikanischen Strafrechts zu dem globalen System des internationalen Strafrechts, in dessen Mittelpunkt der Internationale Strafgerichtshof (IStGH) und der Sicherheitsrat der Vereinten Nationen stehen. Die Kombination der Analysen dieser verschiedenen Bereiche führt die Arbeit zu drei zentralen Schlussfolgerungen: Erstens ist die Entwicklung eines afrikanischen internationalen Strafrechts nicht nur eine Konsequenz der aktuellen Krise des internationalen Strafrechts. Sie ist ebenso und zuvorderst das Ergebnis einer Politik der Eigenständigkeit der AU und ihrer Mitgliedsstaaten. Diese zielt darauf ab, die regionale öffentliche Ordnung durch regionale Institutionen und strafrechtliche Verantwortlichkeit zu schützen. Die zweite Schlussfolgerung lautet, dass die AU ein System regional- afrikanischer Strafjustiz vorantreibt, das auf drei optionalen Modellen aufbaut: Der Delegation von Rechtsprechungsbefugnissen an Mitgliedsstaaten, der Errichtung hybrider Gerichte mit regionalen RichterInnen sowie dem Aufbau eines regionalen Strafgerichtshofs. Zusammen mit solchen Straftatbeständen der Verbrechen gegen den Frieden und die Sicherheit, die den Kontinent spezifisch betreffen, bilden diese Modelle den Kern des afrikanischen internationalen Strafrechts. Allerdings bleiben Tragfähigkeit und Effizienz des Systems problematisch. Es steht vor einer Vielzahl an Herausforderungen, etwa der Ratifikation des Malabo-Protokolls von 2014, das einen „Strafgerichtshof der AU“ errichten soll, der Förderung justizieller Kooperation der Staaten oder der Sicherung einer stabilen Finanzierung des Gerichts. Die dritte Schlussfolgerung lautet, dass ein afrikanisches internationales Strafrecht kein Ersatz für das allgemeine internationale Strafrecht ist. Es geht um die Koexistenz von Normen und Institutionen und eine koordinierte Beziehung, um Kollisionen und Ineffizienzen zu vermeiden. Die Arbeit diskutiert drei verschiedener Ansätze für stabile Beziehungen zwischen dem afrikanisch-regionalen und dem internationalen Strafrecht: Das hierarchische Modell, den kooperativen Ansatz und die Regionalisierung des IStGH in Verbindung mit dem Prinzip der regionalen Territorialität.This study is situated in the context of the regionalisation of international criminal law. It deals with the development of African international criminal law under the aegis of the African Union (AU). It aims to examine the factors which inform this development, the concept and the content of regional law so laid down for the African continent. The primary objective has been the exploration of theoretical and practical bases for the establishment of a viable system of African regional criminal justice in order to deal with crimes against peace and security in Africa, which put in danger African regional public order. The thesis also examines the relationship between African international criminal law and the global system of international criminal justice, currently dominated by the International Criminal Court (ICC) and the United Nations Security Council. The systemic analysis of these different issues have enabled to reach three main conclusions. First, the development of African international criminal law is not simply a conjectural consequence of the crisis observed within global international criminal law. It is also and chiefly the result of the policy of self-reliance of the AU and its member states aiming to protect and defend African regional public order through the recourse to regional institutions of criminal accountability. Second, the African Union is consequently promoting a system of African regional criminal justice based on three optional models of justice, namely the delegation of jurisdiction to a member state, the creation of hybrid courts with participation of regional judges and the establishment of a regional criminal court. Together with those crimes against peace and security that are of specific concern to the African continent, these models of justice form the core of the content of African international criminal law. However, the viability of the system towards delivering efficient justice remains problematic. There are numerous challenges to overcome, including ratifying the Malabo Protocol of June 2014 instituting the “Criminal Court of the African Union”, promoting judicial cooperation of African states and finding financial resources to support the Court’s actions. Third, African international criminal law is not a replacement of global international criminal law in the continent. There is rather a coexistence of norms and institutions which commands a certain degree of coordinated relationships to avoid competing actions and so inefficiency of justice. This thesis discusses two main approaches to consistent relationships between African regional criminal law and the global system of international criminal justice, namely the hierarchical model and the cooperative approach. It proposes a third alternative approach, that is, the regionalisation of the ICC in conjunction with the principle of regional territoriality