Remotely Operated Vehicle (ROV)

 

The first 3,000 m depth rated work-class ROV in Taiwan, which features remarkably performance in full range underwater survey tasks. With full time dedicated ROV team, TORI is aimed to set up an interactive research platform and support deep sea explorations. The ROV is capable of carrying out deep sea observation, sampling, subsea cable inspection, scientific instrument installation, subsea engineering task, emergency accident surveying and exploring marine energy.

 

TORI ROV System

 

TORI’s ROV system is a product of an U.K. company named Forum Subsea Technologies (LARS is not included), the model of which is Triton XLX No.56. The ROV is integrated with two heavy hydraulic manipulators and multiple scientific instruments, a tool skid with payload up to 250 kg is also attached to ROV to provide additional sample storage. There are three main parts of the ROV system which is the vehicle, control room and LARS (Launch and Recovery System), more details are delivered in the following sections.

 

1.     The vehicle

The maximum working depth for the vehicle is 3,000 m, several important deep-sea explorative instruments are equipped,

l  A 150 hp hydraulic power plant, which could provide necessary power to drive 8 thrusters and 2 manipulators. Thrusters on the vehicle are 4 in horizontal and 4 in vertical. For the manipulators, the lifting capacity of the Schilling Titan 4 salve arm is up to 454 kg, and the Kraft Predator slave arm has function of force feedback.

l  11 sets of subsea cameras (including 3 high definition cameras) and 1 set of still camera could provide wide range of instant subsea video feedback, while 4 sets of 400W HMI lights are capable of illuminating the front working area and helpful for color rendition.

l  A scanning sonar could assists pilot in evaluate front obstacles while flying in high disturbance sea waters.

l  An Ultra-Short BaseLine (USBL) and a Homer utilized sound wave transmission to efficiently locate positions between vehicle/research vessel and vehicle/subsea target, respectively.

l  An Inertial Navigation System (INS) integrated with Doppler Velocity Log (DVL) calculates vehicle flying posture and maneuver velocity with respect to ground, allows high precision vehicle navigation and sea floor survey tasks.

 

    

Multiple scientific instruments are mounted on ROV

 

ROV specifications

 

A dedicated tool skid is developed by TORI ROV team to enlarge sample storage capacity, which includes a retractable tool tray and two swing arms providing multiple storage possibility. The ROV could be integrated with the tool skid to fulfill the requirement of adding different explorative instruments and placing wide range of subsea samples.

 

ROV Tool Skid

 

Wide range of sample tools could be stored in the tool tray including scoops, scoop nets, push cores and a bio-box.

 

The hydraulic power plant in the ROV are designed as a water cooling system which requires amount of sea waters to cool down the working temperature. Therefore, its difficult to test or check the functionality of thrusters or manipulators while the vehicle is on deck. A ROV charge cart is used to externally supply hydraulic oil into the vehicle to conduct above mentioned testing procedures.

 

ROV Charge Cart

 

2.     ROV control room

ROV control room is mainly in charge of order control command and access sensor data, which is composed of 2 standard 20ft containers. The control room could be divided into 5 areas according to operational topics including (1) video display area, (2) pilot control area, (3) fiber optical multiplexer rack, (4) high voltage distribution area and (5) scientific monitoring area. There are 13 flat screens mounted in the control room displaying ROV instant video stream, navigation chart, underwater positioning and sonar image to provide all necessary information for deep sea exploration.

 

Floor plan in the ROV control room

 

ROV pilots are operating the vehicle in the control room

 

3.     Launch and Recovery System (LARS)

LARS is the most critical equipment for launching and recovering ROV. A full LARS is consists of Hydraulic Power Unit (HPU), Optical Umbilical Winch and a ROV A-frame.

l  Hydraulic Power Unit, composed of 2 off 75 kW electrical motor and pump unit to provide essential hydraulic power for umbilical winch and A-frame. The HPU is the core equipment of LARS.

l  Optical Umbilical Winch, the interface connecting ROV control room and vehicle. The umbilical is covered by two outer layers of armored wire to sustain ROV weight, while the internal cooper conductor and single mode optical fiber are used respectively for transmitting electrical power and control signal to the vehicle.

l  ROV A-frame, composed of the A-frame and docking head. The safety working load of the A-frame is 8 tons which is mainly assist with delivering the vehicle into and out of the deck. The docking head is used to prevent vehicle over swing during rough sea state launch or recovering. When in launch procedure, umbilical winch pulls up the vehicle and the latch of the docking head grabs ROV bullet. The motion of the vehicle will be limited by the rotational circular stopper of the docking head (until the top of the vehicle reaches to docking head), which could also adjust the vehicle heading. Meanwhile, the vehicle can be delivered out to the sea water by A-frame and ready for launch and vice versa.

 

LARS arrangement on R/V Legend

 

ROV launch at night

 

ROV sea trial in 2018

The research vessel R/V Legend first joined Taiwan ocean scientific research in May of 2018, which provided a stable platform especially for large research equipment. Hence, TORI arranged several sea trials for R/V Legend since the beginning of 2018, a ROV sea trail was also included. The maximum working depth that ROV had been working at was 1,196 m during sea trial, although the number was even lower than the half of the vehicles maximum capacity (which is 3,000 m), but it was the first time that TORI crew finished all of the ROV operational tasks without any assistance from foreign experts. Including vehicle launch and recovery, vehicle subsea flying, selection of dive spots, operation of positioning system and support of navigational sea chart were all successfully conducted. During these dives of 2018 sea trial, ROV had completed several tasks including deep sea animal observation, manipulator sampling, tool skid function test, vehicle auto pilot, gas hydrates observation, mud volcano observation and OBS observation.

 

Different ROV tasks, (A) Coral sampling(B) OBS observation(C) animal observation(D) Vibracore sampling with assistance of manipulator