Abstract-We present an approach for ensuring safety properties of autonomous systems. Our contribution is a system architecture where a policing function validating system safety properties at runtime is separated from the system's intelligent planning function. The policing function is developed formally by a correct-by-construction method. The separation of concerns enables the possibility of replacing and adapting the intelligent planning function without changing the validation approach. We validate our approach on the example of a multi-UAV system managing route generation. Our prototype runtime validator has been integrated and evaluated with an industrial UAV synthetic environment.

In this study, a distributed acoustic sensor (DAS) was numerically modeled based on the non-ideal optical components with their noises and imperfections. This model is used to compare the response of DAS systems to standard single-mode fibers and ultra-low loss-enhanced backscattering (ULEB) fibers, a fiber with an array of high reflective points equally spaced along its length. It is shown that using ULEB fibers with highly reflective points improves the signal-to-noise ratio and linearity of the measurement, compared with the measurement based on standard single-mode fibers.

Distributed acoustic sensing (DAS) systems are a recent technological development for seismic observations over a broad range of frequencies with a wide variety of applications. Typically, fibre-optic cables are buried underground or cemented into well casings where the cables are well-coupled to the ground. Quick and temporary surface deployment of cables has great potential utility in areas where rapid surveying and minimal disturbance of the subsurface are desired. However, proper mechanical coupling between the fibre and the ground is still a challenge for temporary surface deployments. Here we test four different coupling strategies for a DAS system deployed in a grassy field, including uncoupled, pinned under tension to the ground, weighted down by carpeting, and weighted down by a sandbag. We compare the DAS data to vertical component geophone data and estimated horizontal geophone data to assess the fidelity of DAS ground motion recordings. We find a completely uncoupled fibre is capable of recording seismic energy up to ∼10 m away from the source, while the pinned and weighted fibre record signals over several tens of metres. The DAS recordings compare favourably with the estimated horizontal displacement records from the multi-channel seismic system. There is a good agreement between the phase of the signals acquired by the DAS system with that of the geophones, but there is a mismatch of up to a factor of two in the absolute amplitude at some frequencies. We perform several standard analysis techniques, including refraction and multi-channel analysis of surface waves, on the coupled DAS data. Finally, the instrument response of the coupled DAS data to ground motions is determined using the estimated horizontal component from the multi-channel seismic system. Surface deployments of DAS systems provide a complementary set of observations to standard vertical geophone deployments, for instance, if multicomponent geophones are not available. Also, there are some advantages in speed and ease of deployment of DAS in comparison to geophones depending on the coupling strategy used.

In this study, a high spatial resolution distributed acoustic sensor (DAS) with 8 cm gauge length based on ultra low-loss enhanced backscattering (ULEB) fiber with 1 km sensing range is demonstrated.

This paper proposes a new extension to the Event-B modelling method to facilitate the building of hierarchical mathematical libraries to ease the formal modelling of many systems. The challenges are to facilitate building mathematical theories, be compatible with the current method and tools, and to be extensible by users within the Rodin Platform supporting Event-B. Our contribution is a new language, called B , which includes the additional features of type classes and sub-typing. The B language compiles to the current language used by the Rodin's Theory Plug-in, which ensures consistency, and also gives compatibility with the current Rodin tools. We demonstrate the advantages of the new language by comparative examples with the existing Theory Plug-in language.