AUV System Spec Sheet

MARES configuration

Platform: MARES
Manufacturer: University of Porto Ocean Systems Group

Summary

MARES, or Modular Autonomous Robot for Environment Sampling, is a 1.5m long Autonomous Underwater Vehicle (AUV), designed and built by the Ocean Systems Group. The vehicle can be programmed to follow predefined trajectories, while collecting relevant data with the onboard sensors. MARES can dive up to 100m deep, and unlike similar-sized systems, has vertical thrusters to allow for purely vertical motion in the water column. Forward velocity can be independently defined, from 0 to 2 m/s. Major application areas include pollution monitoring, scientific data collection, sonar mapping, underwater video or mine countermeasures.

Main features:

• modular construction, with reconfigurable sections
• spare ports to accomodate payload sensors
• compact and lightweight – fits the trunk of a car
• robust, with fully shrouded moving parts
• operates in confined areas – can ascend/descend in the vertical
• autonomous operation, with simple mission definition
• rechargeable Li-Ion batteries

MARES (Modular Autonomous Robot for Environment Sampling) is a 1.5m long Autonomous Underwater Vehicle that can be configured to carry a wide variety of sensors, collecting data while following predefined trajectories. One of the inovations on MARES is the thruster configuration with no control surfaces, resulting in the ability to hover in the water column, to navigate close to the bottom, or to perform close-up inspections.

Mechanical Structure

MARES’ mechanical structure follows a highly modular approach, with a central hull and several aditional sections, most of them machined in acetal copolymer. Since all sections are mechanical extensions, they can be easily interchanged and it is very simple to insert new sections.

Propulsion and direction are controlled by two independent horizontal thrusters. Another set of thrusters, in the vertical direction, control vertical velocity and pitch angle. The thruster arrangement permits operations in very confined areas, with virtually independent horizontal and vertical motion at velocities starting at 0 m/s.

Electrical Components

The electronic circuits are located in the centrall hull. Energy is provided by Li-Ion batteries, with a total energy of 600 Wh. Depending on vehicle velocity, these batteries can last up to 10 hours, corresponding to about 40km. The main computer is a PC-104 stack, with a power supply, the CPU, a communications board and a solid-state disk.

The navigation system is based on a LBL acoustic network. The vehicle software continuously fuses ranges to the acoustic beacons, together with compass heading and thruster RPM to compute the estimated position.

Payload Sensors

MARES has limited room to accomodate payload, but it is simple to include additional sections and the main hull has several spare connectors to provide energy and communications. Larger payload sensors may also be attached to the outside of the hull.

Mission Programming and Supervision
Before AUV launch, 2 acoustic beacons (typically 2 NIBs) are deployed in the operation area.

MARES missions are programmed using a GUI software, where all mission segments are detailed (waypoints, velocity, depth, …) During the mission, the acoustic beacons transmit vehicle location data to a support vessel, so that the AUV trajectory can be followed in real time. At the end, the vehicle starts transmitting her own position by radio, when at the surface.