Analysis and development of harmless sUAS (small Unmanned Aerial Systems)

The aim of this PhD thesis is the development of a full methodology able to analyze the level of offensiveness of sUAS (small Unmanned Aerial Systems) both with experimental tests and with numerical simulations. As a matter of fact, the exponential growth of the small unmanned configurations marketplace has led to a growing number of accidents between sUAS and the human body. The design of an unmanned configuration must not leave aside the public safety, considering that the main current applications of sUAS, such as media and entertainment, surveillance and terrain monitoring, are performed over crowded areas where the probability of impact with a human body, after a failure on-board or a human error, is higher than in desert areas. Moreover, common people are unaware of risks correlated to the use of sUAS. As a matter of fact, because sUAS are easily bought in common places, such as supermarkets, pilots are generally common and inexperience people, such as children, that use sUAS as toys, for entertainment, without considering the real risks for their safety, but also, and above all, for other people. For instance, the impact of sUAS can cause minor lacerations and abrasions, but also bones’ fracture, serious damages to the internal organs, until the death, as already happened. The unconsciousness of these risks is also demonstrated by the lack of data and general information about the events, because people do not denounce the accident to the competent national regulatory authority, staggering the statistical analyses. National, European and international regulatory authorities are dealing with the safety issue for several years, although, today again, the approaches are different because each authority applies own methodologies and criteria, publishing different regulations periodically upgraded. Although all current regulations are generally based on the same common principles, the final requirements differ, whereby a unique and unequivocal international regulation about the use of sUAS over crowded areas has not been published yet. This delay is causing an unavoidable confusion among stakeholders, such as manufacturers, operators and final and customers because a full methodology able to study the level of offensiveness of sUAS has not been developed yet. A solution to overcome these challenges could be the partial application of automotive approaches, with appropriate considerations and modifications. First of all, the impact of the sUAS with the human body can be studied applying the same injury criteria and relative threshold values required by the automotive regulations from a medical point of view. The impact is defined safe if all these requirements are satisfied for each human body part and not only considering the impact with the human head, that can be defined as the most common, but not the most dangerous impact. Moreover, the analysis of the impact has led to the definition of an analytical model where different criteria and methods developed in other research fields, such as the forensic physics, have been combined, with appropriate considerations, identifying some configuration requirements, but also dynamic features of the unmanned configuration at the impact, such as its kinetic energy. Results of the analytical model have been validated through an experimental test campaign, defined in accordance with the automotive methodology used to perform crash tests. Both the infrastructures and the dummies are the same of the automotive field, although, the crash tests are now specifically related to a sUAS. Because tests have been performed on an existing unmanned configuration, designed without fulfilling the safety requirements, a strategic configuration elements has been added to the sUAS in order to make it an harmless unmanned vehicle. The comparison between the two configurations, with and without this element, has been performed through a wind tunnel test campaign. Because the experimental phase, both crash tests and wind tunnel tests, has an high economical impact and has required a lot of time, the numerical simulation of the impact can be a valid solution to study the accident. These simulations can be also used during the preliminary design phase to analyze the level of offensiveness and the achievement of the safety requirements of the configuration, before the sUAS is manufactured. The comparison between experimental and numerical results has led to the definition of future works with the aim to optimize this methodology, the first one that analyzes an accident scenario and the involved sUAS exhaustively, in order to give to manufacturers, operators and regulatory authorities a valid tool to guarantee the public safety.