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Fibre optic servo bus spans 400m

01 January, 2005

Fibre optic servo bus spans 400m

In 2002, GE Fanuc Automation decided to make a concerted attack on the motion controls market, using a combination of its own control technology and drives produced by its co-owner, Fanuc. At the recent SPS/IPC/Drives show in Germany, it demonstrated some of the first fruits of this strategy.

The key component so far is a four-axis motion controller which communicates by fibre optics to servo motors that can be daisy-chained together over a distance of up to 400m. The DSM324i controller is tightly integrated with GE Fanuc`s PACSystems RX31 programmable automation controller, although it can also be used with an industrial PC or a Series 90-30 PLC.

The 32-bit controller can be used in a centralised or a distributed architecture and offers a choice of incremental or absolute positioning feedback. An electronic gearbox or cam function can follow a master encoder, another axis, or a time-based master source in the control module.

The fibre optic servo bus allows the system`s "almost dumb" servo amplifiers to be up to 100m apart. It is said to cut wiring costs and, unlike Sercos, does not need to be configured.

Fanuc has produced a new range of servo motors to match the controllers. Their built-in encoders incorporate electronic identification boards, which allow plug-and-play installation.

The motors, spanning torque ratings from 0.2-22Nm, are said to be smaller, faster, and more powerful than their predecessors, while operating with a lower inertia. The smallest model is 60mm long including its absolute encoder, and has a flange width of 40mm. It has a top speed of 5,000 rpm.

Fanuc Already produces 60,000 servo motors every month and is planning to step its output up to 100,000 a month this year.

In the next phase of its motion developments, GE Fanuc plans to integrate a multi-axis controller with a PAC system controller and offer motion programming based on PLCopen standards. It is also planning to support interfaces such as Sercos and Profibus Motion.

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