Servo drive for 700 bar deep-sea equipment tasks

17 April 2019

Elmo Motion Control, represented in the UK by Heason Technology, has recently tested a version of its miniature Gold Twitter servo drive at a simulated undersea depth of 7,000 metres.

The Gold Twitter is a miniature yet highly powerful servo drive – capable of up to 2kW continuous power output from a nominal voltage input of 48 to 170 VDC in a package size of just 35 x 30 x 14.4mm. Weighing less than 18-22 grams, the Gold Twitter has minimal mass effect when integrated on mobile equipment and with EtherCAT or CANopen interface options, it is particularly suited to a distributed motion control networking topology.

This modified version of Elmo’s Gold Twitter was developed for typical underwater applications such as deep-sea exploration, oil and gas or naval defence systems where servo drives are used to power or provide robotic functionality for remotely operated vehicles (ROVs) and other autonomous underwater equipment. For many of these areas it is not always possible or cost-effective to provide a fully controlled pressurised vessel to house the servo drive.

The drive was tested at a dedicated facility for high-pressure oil & gas technologies and verified to operate with no compromise to standard specification performance at 700 bar which is approximately 700 times greater than the pressure at sea level.

Heason Technology, with its own design and in-house systems integration capability, is very familiar with the standard Gold Twitter as part of its servo drive range. The drive has been specified as an integral part of custom designed high-precision motion systems comprising bespoke or proprietary positioning mechanics and intelligent motion controls for a wide range of applications across industry, research and defence.

One such example is a custom designed servo actuator that powers the rudder and hydroplane mechanics on a scaled submersible ROV used to evaluate the hydrodynamic design of military submarines. The fully sealed actuator is housed in an oil-filled stainless-steel case and includes active pressure compensation for undersea use. The design brief included pressure testing and certification. Its internal components, sourced from Heason’s distribution partners, include a frameless direct-drive servomotor directly coupled to high-precision and high torque zero-backlash gear system. Capable of a continuous torque output of 12 Nm at speeds of 10 rpm, and with an angular resolution of 0.1º and range of 80º, the unit is powered from an Elmo servo drive housed inside the ROV.