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Novel linear motor system `will open up new machine concepts`
Published:  30 April, 2012

At the recent Hannnover Fair, Beckhoff unveiled a linear motion system that, it says, combines previously distinct advantages of rotary and linear systems. It claims that the XTS (eXtended Transport System) turns previous linear motor principles on their head, and will make completely new machine concepts possible.

The system can move one or more cable-free carriages (known as “movers”) at speeds of up to 4m/s along arbitrary and flexible paths. It comprises: 
•  a modular linear motor with integral power electronics and displacement measurement;
•  one or more cable-free movers;
•  a mechanical guide rail; and
•  an industrial PC running Beckhoff’s TwinCat control software 

The movers contain magnetic plates that interact with coils in the static motor modules to generate propulsive forces. They absorb the attractive forces of the magnets on both sides, allowing rollers on the movers, with low-wear plastic surfaces, to move at high speeds along the guide rails. A robust encoder conveys the mover position to the motor module.

Any number of movers can share one path. They can accelerate, brake, position and synchronise themselves. They can also:
•  take up absolute positions, or position themselves relative to each other;
•  group themselves and accumulate;
•  create clamping forces;
•  drive through curves and along straights;
•  recover energy through regenerative braking; and
•  transport items using both the outward and return paths. 

The motor modules, which contain the electromagnetic coils and all other active components, form complete units with the movers and guide rails. They contain no moving parts and are not subject to wear. The only items needed to complete an installation are a power supply and an EtherCat connection. Complex wiring and drag chains are not needed.

The number and type of components chosen determines the geometry, length and radii of an installation. The outward and return paths, as well as the curves, can be used to transport materials, thus making most effective use of the available space. This reduces the need for hardware and for production space.

Beckoff asserts that the new linear system (shown in close-up above) will open new possibilities for drive technologies. It will, for example, provide linear motor characteristics on an endless path. The modular structure will allow simple adaptations to suit an application. Project engineering and assembly costs should be low, and the system will not need much space or power.

One application area that Beckhoff sees as being particularly promising is high-speed materials-handling. The XTS will be able to push products, adjust their spacing, reduce or increase their speed, and perform actions such as clamping, lifting, closing, rotating and screwing caps into position.

The system will be able to isolate irregular product flows and transfer them at constant intervals and constant speed from one workstation to the next. Products can be picked up and moved rapidly between the workstations, as long as the path is free. Alternatively, they can move to their destination in a travelling buffer. At slow workstations, products can be processed in parallel in groups.

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