Failsafe Mechanism to Hazard Analysis and Risk Mitigation in Unmanned Aerial Vehicle based on NCES

Mohamed Naija, Rihab Khemiri, Ernesto Exposito


In the last few years, Unmanned Aerial Vehicles (UAVs) are receiving more focus in order to execute a wide variety of applications such as the military, agriculture and medical fields. It is known the high vulnerability of the UAV not only to unexpected faults of their software but also to the environment. For this reason, safety should be considered as the main requirement at design time, since any unexpected behavior of the vehicle or any hazard would lead to potential risks. To maintain their safe operation during their missions, a failsafe mechanism based on Net Condition Event System (NCES) is proposed. The failsafe mechanism is a control logic that guides risk reduction actions to be performed when hazards occur. To generate such a controller using formal models, the proposed process is decomposed into three phases: (1) the first phase consists on hazard identification and analysis according to reactive methods of literature, (2) the second phase allows risk estimation using the standard ISO 13849, and (3) the third phase consists of performing reconfiguration scenario in order to risk mitigation while analyzing safety requirements. The motivation behind the use of formal methods is that they have proven to be useful for making the development process reliable at early design stages. We demonstrate the applicability and feasibility of our proposal on an illustrative medical drone as a case study.


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