Underground inspection drone - case study in Barcelona sewage system

Sewage system plays an important role in the infrastructure of cities like Barcelona and needs to be inspected and maintained on a regular basis in order to assure its good operation. The current walkthrough inspection method is tedious, unhealthy and dangerous. From this reality, it was proposed that an autonomous drone carrying needed sensors flies in the sewer and collects the data necessary for the inspection. This thesis studies the integration of drone in the inspection operation of underground infrastructures with a focus on sewage system inspection, in the circumstances of Barcelona city. This study will concentrate on the range sensing methods, particularly range sensing using Lidar, which helps the drone navigate in a closed confined space and in the absence of GNSS navigation. This is crucial in order for the drone to avoid crashing on the walls of the sewer or on other obstacles and accomplish the mission. Several commercial rangefinder sensors are proposed for this project and a comparison is made under several criteria so as to select a best option for the application. Furthermore, this study analyses the requirements for a drone platform conceived for the said application. The architecture of such platform is introduced and evaluated. The building of a practical unmanned aerial vehicle prototype able to perform the inspection is also presented. It was decided that an octocopter of coaxial configuration is the best option for the application, as it allows the platform to have the sufficient power for the application while maintaining its compactness and meanwhile increasing the redundancy and thus improving the security. Details of the key component used in the prototype are presented to give the reader a practical view about the prototype. The result was a prototype of drone platform whose first tests were conducted showing positive results.