The mechanical aspect of the project focused on the machining and integration of a new central section and external battery casings for AUV8.1. The new center section provides mounting points for the batteries, while also increasing the internal volume and improving accessibility to electrical components through dedicated top and side access panels.

The support legs, flotation system, and torpedo launcher mounting point were also redesigned, while the remaining structural components from the original AUV8 were retained. The layout of the eight thrusters was kept similar to the original design in order to preserve the 6 degrees of freedom control system. All machined aluminum parts are powder-coated or anodized to improve durability and provide increased resistance against corrosion in underwater environments.

The internal racking system was redesigned to provide easier access to electrical components while securely holding them in place during operation. All parts are 3D-printed and assembled inside the submarine using reinforced clip-based mounts, resulting in a more secure and rigid installation than the previous design. The layout was optimized to improve space utilization, simplify access to electrical connections, and enhance cable routing throughout the vehicle. Airflow and ventilation were also considered in the design to improve internal circulation and overall system reliability.

The Battery Management System (BMS) is integrated into each battery casing and continuously ensures the safety and health of the battery packs. It monitors the voltage, current, and temperature of each cell to optimize performance and extend battery lifespan.

The system also enables easier charging without removing the batteries from their casings, significantly reducing handling time and minimizing the risk of leaks or water ingress.

The LED communication system was integrated at the front of both submarines to enable inter-vehicle communication by controlling light colour and timing patterns. When the submarines are not communicating with each other, the LEDs are used to transmit real-time status information to operators at poolside.

This new system required the development of a dedicated PCB connected to the submarine’s RS485 network, allowing commands from the onboard computer to be reliably transmitted to the addressable LEDs.

The integration of the ZED Mini stereoscopic camera provides the submarines with 3D perception and enables real-time mapping of the underwater environment. The captured imagery is also used to run the onboard AI system for obstacle detection and recognition, supporting autonomous decision-making during missions.

The ZED Mini was selected for its high-quality depth sensing capabilities as well as its compact form factor, as the larger ZED 2i could not fit within the submarine’s design constraints, making the ZED Mini the optimal choice for balancing performance and integration feasibility.

The new mission system is built using BehaviorTree.CPP and Groot2 to control the high-level behaviour of the submarine. AUV8.1 is the first vehicle in S.O.N.I.A.’s fleet to adopt this architecture.

This new approach offers improved reliability and greater flexibility compared to the previous system. Its modular structure makes it easier to customize mission logic, adapt behaviours, and integrate new autonomous tasks, while maintaining a clear and robust execution flow.