Servo systems drive optical storage jukeboxes

Swiss company ALP Electronics has developed so-called Disk Changer machines, with a capacity of 10,750 disks for up to 100,000 gigabytes; drives and controls are by GE Fanuc

Most of us will know or remember jukeboxes, used in pubs and cafes to play specific music titles.

The basic principle of these machines has now been integrated into an innovative machine concept designed for archiving and managing huge amounts of data.

The drive and control technology used for these machines is provided by GE Fanuc.

With today's rapid development of information technology, the archiving and management of data is becoming an increasingly critical issue.

Thus, the amount of information gathered between 10,000 BC and today is expected to double within the next two years.

Today's companies require new mechanisms and tools in order to store and manage vast quantities of data.

In addition, both private companies and institutions are legally bound to preserve data for a given period.

Based on these needs, the Swiss company ALP Electronics AG has developed so-called Disk Changer machines.

These machines use optical disks and are ideally suited to store and manage large volumes of data.

With a capacity of 10,750 disks for up to 100,000 gigabytes, ALP Electronics currently offers not only the largest but also the most reliable machine of its kind worldwide.

Designed for big libraries, broadcasting stations, national archives, medical archives and large-scale company archives, this machine allows data storage on CDs, DVDs or magneto-optical disks.

To give an impression of the total amount of information that can be stored in this machine, try to imagine it written on endless paper.

The paper roll would go twice around the world! The basic principle of this machine is simple.

The machine is connected to a network.

Any PC connected to the network is capable of carrying out data searches by transmitting a request to one of the two PCs controlling the storage machine.

Both of these PCs are run under OS 9 and work as interpreter between the network server and the PLC located in the machine.

The two computers are designed to be dual redundant, i.e whenever one fails, the other one takes over.

The disks are stored in CD racks on both sides of the machine.

Each side of the machine is equipped with a pneumatic robot which retrieves the desired disk from the rack and inserts it into one of 320 possible drives whenever instructed by the PLC to do so.

From there, the information is read, checked and transmitted to the two machine PCs or to the network server.

In just one minute, the system is able to provide approximately 100 MB of data.

Previous machines, using a tape-based technology, would take twice that time.

The insertion/withdrawal of the disks into and from the machine is carried manually using modules with a capacity of 200 disks each.

This is possible while the machine is running.

When ALP Electronics started to elaborate the machine concept, the developers were aware that they required a top-quality drive and control technology.

With GE Fanuc, they found a partner who not only supplied the products but also contributed their long experience and know-how to the development of the drive and control concept.

The concept includes two Series 90-30 PLCs, eight digital Beta servo motors and eight digital servo amplifiers.

The machine is monitored by the Cimplicity software which runs under Windows NT and collects data from 75 data points.

The communication between the two OS9 computers, the Cimplicity PC and the controllers is carried out via Ethernet TCP/IP using the SRTP protocol.

For faster installation and better maintenance, a Quickpanel Handy was integrated in the concept.

The PLCs each have 96 digital inputs and 64 digital outputs.

The PLC controls the amplifiers and motors via the DSM 302 module and was programmed in Ladder using the Windows-based VersaPro programming language.

For the robot to withdraw the CDs from the racks, the machine requires a very accurate and precise positioning of axes.

This can only be achieved by digital drive technology.

For such kind of high-precision applications, GE Fanuc has developed an intelligent solution combining PLC technology with digital drive technology.

Using the DSM 302 serial interface from GE Fanuc, the controller is able to communicate with the digital servo amplifiers/motors via the PWM (Pulse Width Modulation) protocol.

The PLC thus easily controls parameters such as torque, speed and acceleration, with only one memory location used for each parameter stored in the CPU.

As a result, maintenance becomes easier and faster.

Simple CPU uploads/downloads take care of modifications in the PLC and double words (32bit) are used to improve the positioning accuracy.

With the intelligent drive and control concept, GE Fanuc was able to offer a cost-efficient solution.

A further major reason to select GE Fanuc is explained by Yann Delamadeleine, Technical Manager at ALP Electronic.

"The reliability of GE Fanuc products is well-known.

But in the unlikely event of a problem, I can now also rely on GE Fanuc's global presence throughout the world.

For us as an export-oriented company, this can be decisive." Another statement made by Delamadeleine illustrates an important trend in the automation sector: "With GE Fanuc, we have not only received all drive and control products from a single source, but also their competent technical know-how as to planning and implementation." Good products is no longer the only thing expected from automation manufacturers.

What customers increasingly want are intelligent overall solutions.

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