P. Baldi

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.

A new longitudinal flight path control with adaptive wind shear estimation and compensation

This paper presents a novel approach to the longitudinal guidance and control issue for an aircraft in presence of wind shear. The main contribution concerns the adaptive estimation of the wind shear disturbances affecting the aircraft and the development of a control scheme suitable to compensate these effects during a precision approach procedure. The work proposes the design, based on the Nonlinear Geometric Approach, of three adaptive filters providing the estimate of the wind shear disturbance components. These estimates are exploited, in an original way, by a BackStepping based controller, thus resulting in an Adaptive BackStepping Controller. Simulation results, obtained by means of a detailed flight simulator implementing the real wind shear condition which caused the 1975 crash of Eastern Flight 066 at JFK airport and a Montecarlo robustness test, demonstrates the effectiveness of the proposed method.

Adaptive FTC based on control allocation and fault accommodation for satellite reaction wheels

This paper proposes an active fault tolerant control scheme to cope with faults or failures affecting the flywheel spin rate sensors or satellite reaction wheel motors. The active fault tolerant control system consists of a fault detection and diagnosis module along with a control allocation and fault accommodation module directly exploiting the on-line fault estimates. The use of the nonlinear geometric approach and radial basis function neural networks allows to obtain a precise fault isolation, independently from the knowledge of aerodynamic disturbance parameters, and to design generalised estimation filters, which do not need a priori information about the internal model of the signal to be estimated. The adaptive control allocation and sensor fault accommodation can handle both temporal faults and failures. Simulation results illustrate the convincing fault correction and attitude control performances of the proposed system.

Generic wind estimation and compensation based on NLGA and RBF-NN

This paper proposes a solution to the aircraft control problem during landing phases in presence of microburst wind shear. This work addresses the design of an adaptive controller which, exploiting the wind estimation provided by suitable filters, improves the flight safety and is able to accomplish the final approach phase even in presence of wind shear. The adaptive controller has been designed by using a backstepping approach and a feedback linearization for time-varying systems. The wind components are estimated by adaptive filters designed by using the tools of both the nonlinear geometric approach and the radial basis function neural network.

Aerodynamic Decoupled FDI for Frequency Faults in Earth Satellite Engines

Abstract This paper presents new results regarding the development of a fault detection and isolation scheme for a nonlinear satellite model. The main issue concerns the handling of frequency faults affecting the reaction wheels of a spacecraft attitude control system, i.e. how to detect and isolate faults, and lastly how to determine the different frequencies characterising these faults through spectral analysis. As the study focusses 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 via a nonlinear geometric approach. In order to achieve accurate fault diagnosis, aerodynamic disturbance decoupling represents a key point, since the aerodynamic model is often uncertain. Moreover, an improvement of the nonlinear geometric approach is presented, in order to realise an aerodynamic decoupled fault diagnosis with normalized fault sensitivity. To the best authors’ knowledge, this is the first works presenting a methodology for frequency fault diagnosis which is based on the nonlinear geometric approach for the fault and disturbance decoupling. The obtained results demonstrate that the proposed methodology can achieve better performances with respect to traditional fault detection and isolation schemes.