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Technology - the TriMARES AUV/ROV

TriMARES is a 3-body autonomous underwater vehicle, designed to provided extra payload capability, including high quality video and sonar. The physical arrangement ensures motion smoothness for improved quality in payload and positioning data.  TriMARES motion is provided by seven independent thrusters, 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 of underwater structures. If necessary, a very thin fiber optic cable can be attached to provide real time sensor information.

Mechanical Structure and Propulsion

The TriMARES' mechanical arrangement follows a modular approach, with three main bodies linked by a light mechanical structure, holding the structure together and hiding interconnect cables. Each body is assembled with interchangeable cylindrical sections.

Horizontal propulsion and direction are controlled by four independent thrusters located at the stern. Another set of thrusters, in the vertical direction, control vertical velocity and pitch angle. A single lateral thruster provides sway motion.

The thruster arrangement permits operations in very confined areas, with virtually independent horizontal, vertical, and lateral motion at velocities starting at 0 m/s.

Electrical Components

Energy is provided by rechargeable Li-Ion batteries located in the lower pod, with a total energy of 800 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 located in the upper starboard body, 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, inertial data and thruster RPM to compute the estimated position.

When the vehicle surfaces, a GPS receiver provides absolute position and communications may be established using Wi-Fi or a UHF radio link.

Payload Sensors

TriMARES has spare cylindrical sections to accommodate payload sensors, such as video and sonars, and it is simple to include further modules if required. All end caps have spare connectors to provide energy and communications.

Larger payload sensors may also be attached to the mechanical structure and buoyancy can be trimmed by removing ballast weights or adding extra flotation.

Vehicle Operation

Before vehicle launch, two acoustic beacons are deployed in the operation area to provide a baseline for LBL navigation.

TriMARES missions may be programmed as an AUV using a GUI software, where all mission segments are detailed (waypoints, velocity, depth, ...). During these missions, there is no communication with the vehicle, although it is possible to track the position through acoustics. Alternatively, the operator may chose to connect the fiber optic umbilical to provide a high speed link for realtime data transmission and, if required, to steer the vehicle as an ROV.


Vehicle Status

Jun'11 - TriMARES shipped to Brazil.

May'11 - Full system validation in Douro river.

Mar'11 - First trials in test tank, ROV and AUV operations.

Feb'11 - Vehicle fully assembled.

Jan'11 - Computational systems completed.

Dec'10 - Validation of energy management module (lower pod).

Sep'10 - First mechanical parts delivered.

Aug'10 - Contract signed, definition of main AUV requirements.


Overview of TriMARES AUV


Vehicle specs:


1.3 m

Overall Width

80 cm

Overall Height 50 cm

Weight in Air

75 kg

Depth Rating

100 m

Horizontal Velocity

0-2 m/s, variable


about 10 hrs / 40 km




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