LVIT'S for Subsea ROVs - Linear Position Sensors

Hello, and thank you for choosing Harold G. Schaevitz Industries - Alliance Sensors Group. Today we will be discussing the use of LVIT position sensor technology in Submersible Remotely Operated Vehicles (ROVs).

LVITs (Linear Variable Inductance Transducers) are contactless linear position sensors that offer high reliability, durability, and performance at reasonable cost. These features make them ideal sensors for various internal systems functions in many Remotely Operated Vehicles (ROVs) for subsea activities. 

Typical ROV system functions include maneuvering controls; rudder and directional positioning controls; stability augmentation; and tool gripper or robotic arm operation. LVITs can also be used with interactive manual controls in a ROV's remote control console.

In most ROV applications, an LVIT position sensor is a feedback element in a closed-loop servo system. In a typical example, LVIT sensors may be mechanically connected to gimbals on the propeller shaft to provide feedback to the ECU that is operating the gimbals' servos. When used in ROV steering systems, LVITs can give position feedback about the vehicle's rudder and diving planes orientation that comports with the algorithms being used within the ROV's position control system.

One style of LVIT position sensors that works very well with ROV tool grippers is ASG's SSx-7 series of subsea sensors, available for SAE or ISO O-ring port mounting to function within the hydraulic actuators operating the ROV's grippers. The SSx-7 series are very robust sensors that can be used directly in sea water to depths of 11,000 feet (3,300 m) or in PBOF environments up to 5000 psig (350 bar). ASG also offers the MHE-7 series of internally-embedded cylinder position sensors. All in-cylinder sensors utilize a gun-drilled blind hole down the center of the hydraulic cylinder rod to measure the actuator position. The SSx-7 and MHE-7 in-cylinder LVITs are available in ranges from 1 inch (25 mm) to 36 inches (900 mm).

The contactless inductive nature of LVITs is a standout feature of these low cost, high reliability position sensors. Being contactless means there is no internal electrical contact that can wear out, particularly from vibration. Also, the fact that LVITs are DC in, DC out devices minimizes the need for any auxiliary electronics. LVITs are also available with various bus-ready digital outputs to connect to many common microcontrollers. And their low input power requirement makes LVITs well suited to subsea operation.

A really important advantage for LVIT position sensors in ROVs is their very favorable stroke-to-length ratio, which makes it easy to fit LVITs into an ROV’s internal mechanical systems with limited space. A further feature is the ability of ASG to develop customized subsea sensors in small quantities, including various subsea connectors, O-ring port fittings, alternative materials of construction, and digital I/Os.

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