A Model based Safety Assessment for Multirotors

Unmanned Aerial Vehicles (UAVs) must be safe and reliable to prevent fatal accidents in densely populated areas. This research makes the first steps to create a framework which can integrate safety and reliability considerations in the design process. The conceptual design process should consider creating design models coupling sizing with system architecture. Additionally, the multirotor has safety challenges from the propulsor configuration. They lose flight control and show erroneous flight behaviour when propulsors fail. Hence, the design models of multirotor should also incorporate a controllability assessment method to identify and isolate uncontrollable events. For this matter, an appropriate tool should be considered to create such design models. A combination of OpenAltarica, System Analyst and Python is used to create design models of multirotor in a model-based safety assessment framework. These models are developed by integrating system architecture and controllability assessment following the etiquettes of the process. A case study is used to validate the framework and to demonstrate its ability to explore innovative designs. The reliability analysis confirms that the multirotors are fault-tolerant except quadrotor and some configurations are potentially highly reliable. The results demonstrate the feasibility of the multirotor system modelling methods in terms of reliability and pave the way to further develop the model-based safety assessment framework with sizing methodologies. The models can also be further enhanced with the addition of a component fault library, additional failure modes and implementation of diagnosability analysis, fault detection and identification analysis. Fault libraries and failure modes can help in foreseeing uncontrollable cases. In contrast, diagnosability analysis, fault detection and identification analysis can integrate detect, isolate and recover mechanisms, and ensure redundancy optimization effectively. Additionally, the framework should also be combined with multidisciplinary design optimization for sizing. Such design models can contribute to the emergence of UAVs for safety-critical applications