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New approach enables linear motors to move in two axes

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New approach enables linear motors to move in two axesResearchers at Philips Applied Technologies have developed a highly innovative technique that enables standard linear motors to simultaneously provide movement along two axes rather than along a single axis. In equipment such as pick-and-place machines used to assemble electronic printed circuit boards, Philips' patented NForcer Technology enables designers to reduce the number of motors and electronic drive modules required, as well as simplifying the overall mechanical design. This will result in significantly lower equipment cost. Furthermore, by reducing the mass of moving parts, it will also result in designs that achieve higher accelerations and operating speeds.

This new innovation enables horizontally-mounted linear motors to generate lift as well as lateral motion, providing both axes of motion required in pick-and-place machines from just one motor. NForcer Technology also enables the production of precision magnetically levitated platforms with six axes of controlled motion (three-dimensional shifts and tilts) by using ordinary linear motors.

Dr. Georgo Angelis, Senior Scientist at Philips Applied Technologies, states: "The beauty of this new innovation in linear motor operation is that it requires absolutely no modification to existing motor components. All you need to do is reposition the components slightly and drive them in an intelligent way."

How it works

Iron-less, multi-phase linear motors rely on the fact that a current-carrying conductor placed in a magnetic field experiences a force perpendicular to the direction of the current and the direction of the field (the Lorentz force). It is this force that creates the motion. In a conventional linear motor, the current-carrying conductors are arranged in coils, with only the vertical sides of the coils in the magnetic field. As a result, the motor only generates lateral motion. To achieve two-dimensional motion from one motor, the researchers at Philips Applied Technologies have shifted the position of the coils with respect to the magnet track so that the lower horizontal section of the coils also sits in the magnetic field, where it generates force and consequent motion in the vertical direction.

Because the NForcer Technology can be used to implement magnetic levitation, it will permit the production of fully floating, bearing-less platforms, which, unlike air-bearing platforms, can be used in a vacuum. A fully floating, magnetically levitated (bearing-less) platform with long-stroke x-axis, short-stroke y- and z-axis movements and a few milli-radians of tilt and turn can be implemented with only four horizontal magnet tracks (stators) and six forcers (rotors).

The development of Philips Applied Technologies' NForcer Technology stems from the company's long history in providing industry with advanced mechatronic systems, ranging from CD-ROM drive servo mechanisms to ultra-precise positioning platforms for silicon chip manufacturing.

Philips Applied Technologies is demonstrating its NForcer Technology at the ASPE (American Society for Precision Engineering) Annual Meeting (14-19 October 2007, Dallas, Texas, USA). These demonstrations include a single-track roller bearing pick-and-place mechanism with 200mm horizontal and 30mm vertical movements achieved with a single forcer, and a magnetically levitated platform movable with six degrees of freedom with nanometre accuracy. Both demonstrators are constructed from standard 'off-the-shelf' motor components.

15 October 2007

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