Online system identification for fault tolerant control of unmanned aerial vehicles

[摘要] ENGLISH ABSTRACT: In this thesis the strategy for performing System Identification on an aircraft is presented. Theultimate aim of this document is to outline the steps required for successful aircraft parameterestimation within a Fault Tolerant Control Framework.A brief derivation of the classical 6 degree-of-freedom aircraft model is firstly presented. Thederivation gives insight into the aircraft dynamics that are to be used to estimate the aircraftparameters, and provides a basis for the methods provided in this thesis.Different techniques of System Identification were evaluated, resulting in the choice of theRegression method to be used. This method, based on the Least-Squares method, is chosenbecause of its simplicity of use and because it does not require as much computational time asthe other methods presented. Regression methods, including a recursive algorithm, are thenapplied to aircraft parameter estimation and practical considerations such as Identifiability andcorrupted measurements are highlighted.The determination of unknown measurements required for System Identification of aircraftparameters is then discussed. Methods for both estimating and measuring the Angle-of-Attack(AoA) and angular accelerations are presented. The design and calibration of an AoA probefor AoA measurements, as well as a novel method that uses distributed sensors to determinethe angular accelerations is also presented.The techniques presented in this thesis are then tested on a non-linear aircraft model. Throughsimulation it was shown that for the given sensor setup, the methods do not providesufficiently accurate parameter estimates. When using the Regression method, obtainingmeasurements of the angle-of-attack solely through estimation causes problems in theestimation of the aerodynamic lift coefficients.Flight tests were performed and the data was analyzed. Similar issues as experienced withestimation done on the non-linear aircraft simulation, was found. Recommendations withregards to how to conduct future flight tests for system identification is proposed and possible sources of errors are highlighted.

[发布机构] Stellenbosch University