This aerial drone, developed by the University of the Balearic Islands, is intended to address the operational scenario involving wide volumes with a reduced number of obstacles and irregular surfaces, like cargo holds and cargo tanks. The platform is characterized by a rich equipment of sensors and software technology for highly autonomous unsupervised navigation, able to explore wide spaces according to complex path planning.
The drone developed by the UIB team addresses the visual inspection of vessel cargo holds. To this end, it has been configured, in terms of equipment, locomotion abilities and operational features, to satisfy the scope of the survey activities, aiming at safer, more cost-efficient and more intensive visual inspection of wide spaces.
Starting from the aerial platforms developed along previous inspection-related projects in which the UIB team has participated, and taking into account the lessons learnt during the respective field trials, several options about structure, control approach, platform localization, inspection-oriented capabilities to incorporate and interface with the user have been considered, solved and integrated to increase the Technology Readiness Level (TRL) of the whole inspection solution.
For a start, a multi-rotor platform has been used as a basis of the mechanical structure, being fitted with a sensor suite intended to provide the pilot with enhanced functionality and autonomy during inspection flights, and as well supply the required inspection data, i.e. imagery, from the relevant areas.
In order to provide the platform with the necessary capabilities, a control architecture has been specifically designed and developed around the Supervised Autonomy (SA) control model, by means of extensive use of behaviour-based high-level control (including obstacle detection and collision prevention), all specifically devised for visual inspection. Accordingly, after analysing the visual inspection application, a number of suitable behaviours oriented towards visual inspection have been defined and integrated.
Figure 2 – High-level view of the inspection-oriented control architecture
The aerial platform is complemented with a Base Station (BS), comprising a Ground Control Unit (GCU) and suitable Hardware Interaction Devices (HID) to facilitate the interaction with the MAV and as well collect and process inspection data. Special emphasis has been put on the design of the BS to shorten the deployment times once in the field.
Usability and assistance to inspection operations, and how the supervised autonomy paradigm can contribute to both, have been key issues along the different developments that have been undertaken, either regarding the platform itself or the BS, and at all levels, hardware and software.
Successful performance, in the form of both qualitative and quantitative results, has been reported for a set of experiments aiming at assessing the different functionalities of the platform. The full system has been evaluated both within the laboratory and out of the laboratory, on-board real vessels. The laboratory experiments have allowed us to check in detail and accurately the different functionalities of the platform, both at the scale of the laboratory and at a wider in-campus facility that has allowed us to continue the systematic assessment of the platform. On the other side, field trials, with the presence of surveyors guiding the experimentation, have permitted evaluating the platform under conditions closer to the final use.
Results show the platform effective for visual inspection due to the inspection-oriented capabilities it has been fitted with.
Figure 3: Pictures from field trials on-board a bulk carrier (bottom: plot of 18 x 6 m sweeping performed in a cargo hold)