15 October, 2007

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Rethinking the way linear motors are driven allows a single motor to generate movement in two directions, providing much simplified and higher performance motion systems.

 

Researchers at Philips Applied Technologies have developed a highly innovative technique that allows standard linear motors to simultaneously provide movement along two axes rather than along a single axis. In equipment such as the ‘pick-and-place’ machines used to assemble electronic printed circuit boards, Philips’ patented ‘NForcer Technology' will allow designers to reduce the number of motors and electronic drive modules required as well as simplifying overall mechanical design. This will result in significantly lower equipment cost. By reducing the mass of moving parts, it will also allow designers to produce 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 (3-dimensional shifts and tilts) by using ordinary linear motors.

 

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

 

Principle of operation

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 2-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 Philips’ NForcer Technology can be used to implement magnetic levitation, it will allow the production of fully floating, bearing-less platforms, which unlike air-bearing solutions can be used in 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 solutions, ranging from CD-ROM drive servo mechanisms to ultra-precise positioning platforms for silicon chip manufacturing.

 

Figure 1

 

Philips Applied Technologies is demonstrating its NForcer Technology at this year’s ASPE (American Society for Precision Engineering) Annual Meeting (October 14 - 19, 2007, Dallas, Texas). These demonstrations include a single-track roller bearing pick-and-place mechanism with 20-cm horizontal and 3-cm vertical movements achieved with a single forcer, and a magnetically levitated platform movable in six degrees of freedom with nanometer accuracy (see Figure 1). Both demonstrators are constructed from standard ‘off-the-shelf’ motor components.