G. Bertoni

Fault diagnosis and control reconfiguration for satellite reaction wheels

This paper presents preliminary results regarding the development of a supervision scheme for the attitude control system of a nonlinear satellite model. The main issue concerns the handling of faults affecting the reaction wheels, i.e. how to detect and isolate faults, and how to prevent propagation into failures with potential mission loss as a consequence. Thus, this work investigates the design of a scheme for fault detection, isolation and control reconfiguration applied to the reaction wheels of a spacecraft attitude control, based on the satellite model. As the study focuses on a general satellite nonlinear model, where aerodynamic and gravitational disturbances, as well as measurement errors are present, the robustness of the suggested strategy is achieved by exploiting an explicit disturbance decoupling method. The results obtained demonstrate how the proposed methodology can constitute a successful approach for real application in future spacecraft.

Aircraft Guidance Law Analysis

Abstract This paper proposes an alternative formulation of the guidance problem, particularly suitable in autonomous aircraft applications. The Lyapunovs direct method is adopted as main tool to prove some properties of the considered guidance law. The aim of this work is designing a new feedback implemented algorithm that asymptotically stabilizes a generic aircraft to the imposed reference bearing in a local earth reference frame, instead of the velocity vector stabilization towards a reference way-point.

A nonlinear guidance and active fault tolerant control system for a fixed wing Unmanned Aerial Vehicle

By using an interactive architecture of independently designed guidance and active fault tolerant control systems, this work proposes the development of a novel Guidance and Active Fault Tolerant Control Scheme for a fixed wing Unmanned Aerial Vehicle. As to the guidance segment, an approach, of the Feedback Linearization type, has been exploited for developing, directly on the dynamic model of the fixed wing Unmanned Aerial Vehicle, the guidance system. With reference to the control segment, this paper proposes a novel Active Fault Tolerant Control Scheme based on Adaptive Filters designed by means of the NonLinear Geometric Approach. The aim of these adaptive filters is to provide a fault estimate, which is used in a further control loop, thus avoiding a logic-based switching controller. The simulation results show good tracking capabilities, asymptotic fault accommodation and a stability analysis with respect to perturbed initial condition. Finally a comparison with the performance obtained by using the fault estimate obtained by another method is given.

The GPS Integrity Problem

Abstract In those systems where safety is a primary design constrain, the necessity to immediately alert the process manager about hazardous situations arises; according to the ICAO-RPN recent regulations, integrity expresses the probability to recognize these situations in a stated time. Using a suitable redundancy in the sensors of the state variables under control, in the following article a methodology to satisfy the integrity requirement also in critical conditions as terminal area approaching is illustrated. The aim is to single out a sistematic error on distance measurements in a noisy environment.

Reduced Order Regulators for Large Scale Systems: A Numerical Implementation for Stochastic and Deterministic Systems

Abstract The need of introducing dynamic regulators in high order dynamic system is getting stronger in many fields of activity; unfortunately using the dynamic regulators given by the classical methods in the optimum control theory implies serious shortcomings due to their high dynamical order. A promising way for properly solving this protlem is to feed hack the system using a reduced order dynamic regulator which is numerically implemented and minimizes a proper performance index. In the current literature, this problem has been solved only in the stochastic case, that is when the disturbances entering the system and the noise affecting the measurements have known statistic properties; in the so called deterministic case (which really, does not mean that the disturbances are not present but have unknown statistic properties) no solution has teen given up to now. The present paper aims to present a unified numerical procedure for implementing a reduced order optimal regulator using the same algorithm (and hence the same computer program) for both cases, the only difference being the use of proper constraints in order to obtain suitable poles in the deterministic case.

Postgraduate Education on Fault Diagnosis and Control Reconfiguration in Aerospace

Abstract The computer-aided teaching process has increased the interaction between students and professors thus improving the learning process. The goal of courses for graduate students is to teach both a higher level of theoretical and methodological matters and how to design systems. This goal needs a project-based education that is an education performed while implementing a project. In the present paper, our project-based education deals with the implementation of an AFTCS (Active Fault Tolerant Control System) for a UAS (Unmanned Aerial System). The activity to be dealt with is twofold: one is of a methodological type and the other of a technical applicative type.

DEIS UAV: GNC Design and Avionics Implementation Issues

Abstract The School of Aerospace Engineering of the Forli Branch of the University of Bologna is currently developing an Unmanned Aerial Vehicle (UAV) which, thanks to a partially autonomous flight capability, aims to be a very low cost and compact flying platform capable of performing significant flight tests of general GNC algorithms or mission oriented experiments. The development activity includes the project, the synthesis and the assembly of the on-board avionics equipment, together with the software implementation for both data collection and some basic GNC algorithms. A demonstrative application will be the test of some integrity monitoring functions and algorithms using data collected during some flights.

ENHANCED ROBUSTNESS FOR PITCH POINTING FLIGHT USING SLIDING MODE CONTROL

Abstract This paper proposes a methodology of combining eigenstructure assignment, feedforward gain with sliding mode control technique to realize an enhanced robust pitch pointing flight control system. This control system can track step input commands without error and it turns out to be consistently robust against parameter variations and external disturbances. The design methodology is illustrated by application to an AFTI/F-16 aircraft.

Integrated Control of Distributed Parameter Systems

Abstract This work develops a new method for designing low-order dynamic compensators. This design procedure integrates the LOG-based reduced-order dynamic compensator synthesis with the low-authority algebraic controller synthesis. A comparison with a well-known method which exploits similar concepts is also presented

AIRCRAFT GUIDANCE LAW WITH TRAJECTORY CONSTRAINTS

Abstract This paper presents two new algorithms with guidance purposes for autonomous aircraft applications. The adopted approach to the guidance problem is based on a reference bearing instead of the classical way–point. The new guidance laws are an extension of an earlier nonlinear algorithm and are designed in the framework of variable structure systems. The aim of the new guidance laws is to improve the aircraft trajectory during wide-angle turns, if the motion is restricted to a plane, by constraining the radius of curvature.