Chapter 15 Characterization and Prognosis of Multirotor Failures Joseph M. Brown, Jesse A. Coffey, Dustin Harvey, and Jordan M. Thayer Abstract Multirotor (MR) unmanned aviation systems are becoming more prevalent in the commercial, philanthropic, and military communities. Because of these public environment applications, hardware malfunctions pose serious safety concerns. Propeller, motor, and structural damage can cause substantial failure of the MR vehicle and endanger surrounding people and structures; thus, early identification and prognosis of these failure modes is necessary to mitigate harm. An embedded structural health monitoring (SHM) system is optimal for identification and diagnosis of these failure modes in time to alter or abort the mission. To achieve autonomous SHM, statistical data must be accrued from a series of sensor measurements. This information is utilized in the development of appropriate damage metrics for failure modes of interest, which determine the real-time state of hardware elements. A comprehensive sensor network was successfully designed and implemented on an MR vehicle to determine which instruments provide valuable information. Utilizing this relevant data, a compatible set of tools was developed for signal processing, and the resulting SHM system is capable of classifying propeller, motor, and structural hardware failures. Keywords Unmanned Aerial Vehicle • UAV • Multirotor Vehicle • Damage Prognosis • Structural Health Monitoring 15.1 Introduction 15.1.1 Motivation Multirotor (MR) Unmanned Aerial Vehicles (UAVs) are becoming increasingly prevalent in modern society, as they have a wide array of applications in a variety of industries. The military uses UAVs to save soldiers’ lives in otherwise hazardous situations [1]. Commercial corporations such as Amazon and UPS are researching the use of UAVs for speedy delivery of packages [2]. Philanthropic and medical groups have investigated UAVs extensively in order to quickly deliver medical supplies to areas with limited road access [3]. Some predict that, in the future, UAVs could be used for common transportation in major cities. Currently, the United States Federal Aviation Administration (FAA) has restrictions on the types of vehicles permitted to fly; however, changes in favor of unmanned aerial vehicle use are anticipated [4]. Because commercial use of UAVs is likely, steps must be taken to ensure their safe operation. Unmanned aircrafts used in uncontrolled areas pose a risk to the general public. As devices with several complex moving components, UAVs are susceptible to a variety of mechanical failures. For example, high-speed motors and propellers induce vibrations that weaken the airframe or fatigue joints over time. The lithium-polymer batteries used to power the aircraft pose a fire risk if the vehicle crashes, especially in a dry area. Failure of an aircraft’s navigation system or sensors could misdirect the flight of a UAV and result in component failures leading to a crash [5]. In order to address these safety concerns, operators J.M. Brown Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA J.A. Coffey III Department of Aeronautical and Astronautical Engineering, Stanford University, Stanford, CA 94305, USA D. Harvey ( ) Department of Structural Engineering, University of California San Diego, San Diego, CA 92093, USA e-mail: harveydy@lanl.gov J.M. Thayer Department of Mechanical Engineering, University of Southern California, Los Angeles, CA 90007, USA © The Society for Experimental Mechanics, Inc. 2015 C. Niezrecki (ed.), Structural Health Monitoring and Damage Detection, Volume 7, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-15230-1_15 157
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