Fault Tolerant Control of Multirotor UAV for Piloted Outdoor Flights

TL;DR

This paper develops a fault-tolerant control architecture for multirotor UAVs that maintains controllability after actuator failures, validated through indoor and outdoor tests on a quadrotor platform.

Contribution

It introduces a novel FTC framework based on AVCS analysis, including control allocation and calibration routines, for improved UAV fault tolerance.

Findings

Successful fault-tolerant control in outdoor flights

Effective control allocation with pseudo-inverse and desaturation

Improved IMU calibration for high-speed spins

Abstract

This paper aims to develop a Fault Tolerant Control (FTC) architecture, for the case of a damaged actuator for a multirotor UAV that can be applied across multirotor platforms based on their Attainable Virtual Control Set (AVCS). The research is aimed to study the AVCS and identify the parameters that limit the controllability of multirotor UAV post an actuator failure. Based on the study of controllability, the requirements for a FTC is laid out. The implemented control solution will be tested on a quadrotor, Intel Shooting Star UAV platform in indoor and outdoor flights using only the onboard sensors. The attitude control solution is implemented with reduced attitude control, and the control allocation is performed with pseudo-inverse based model inversion with sequential desaturation to ensure tilt priority. The model is identified with an offline Ordinary Least Squares routine and subsequently updated with the Recursive Least Squares method. An offline calibration routine is implemented to correct IMU offset distance from the centre of rotation to correct for accelerometer bias caused by the high-speed spin after failure in a quadrotor.