Fault Estimation and Fault Tolerant Control Strategies Applied to VTOL Aerial Vehicles With Soft and Aggressive Actuator Faults

Gerardo Ortiz-Torres,Jesse Y Rumbo-Morales,Jorge A Brizuela-Mendoza,Pedro Castillo,Mario Martinez-Garcia,Felipe D J Sorcia-Vazquez,Javier De La Cruz-Soto

doi:10.1109/access.2019.2963693

Abstract

Actuator Fault Estimation (FE) and Fault Tolerant Control (FTC) strategies designed with model-based observers for Vertical Take-Off and Landing (VTOL) aerial vehicles are proposed and validated experimentally in this paper. Three observers are considered for FE: a nonlinear adaptive observer and a linear Proportional-Integral Observer (PIO) applied to a Planar VTOL and a quasi-Linear Parameter Varying (qLPV) PIO applied to a quadcopter vehicle. The fault detection is done by comparing the fault estimation signal with a predefined threshold. Fault isolation is achieved by analyzing the sign of the fault estimation signal. The Available Control Authority Index (ACAI) method is used to analyze the controllability properties of the vehicles under actuator faults. The main contribution of this work is the design and the experimental validation of complete active FTC schemes by using the proposed FE systems in order to accommodate a soft actuator fault and reconfigure an aggressive fault, even when the vehicle is flying in a non-hover position. Finally, the proposed FTC schemes are validated in different cases of flight tests for illustrating the effectiveness of the strategies.

Highlights

In the last years multicopter configurations for Unmanned Aerial Vehicles (UAVs) have become promising mobile platforms capable of navigating autonomously in uncertain environments
The main contribution of this work is the design and the experimental validation of complete active Fault Tolerant Control (FTC) schemes by using the proposed Fault Estimation (FE) systems in order to accommodate a soft actuator fault and reconfigure an aggressive fault, even when the vehicle is flying in a non-hover position
This paper presents Fault Diagnosis (FD) systems designed with three Fault Estimation (FE) observers for Vertical Take-Off and Landing (VTOL) vehicles: a nonlinear Adaptive Observer (AO) and a linear Proportional-Integral Observer (PIO) both applied to a PVTOL aircraft, and a quasi-Linear Parameter Varying (qLPV) PIO applied to a quadcopter vehicle

Summary

Introduction

In the last years multicopter configurations for Unmanned Aerial Vehicles (UAVs) have become promising mobile platforms capable of navigating (semi) autonomously in uncertain environments. Numerous applications for this kind of vehicles have been proposed, as aerial photography, surveillance, crop spraying, oil spill detection, supply delivery, fire monitoring, agriculture assessment, communications monitoring, among others [1]. With the increase of applications and the high degree of integrating automation technology, the VTOL aircraft have become progressively vulnerable to faults which inevitably influence the dynamics of the vehicle affecting the stability, reliability, and safety during the flight envelope. Some works have considered actuator FD for quadcopters: in [6], an experimental applications

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