Researchers at Philips Applied Technologies, Dallas, Tex., (www.apptech.philips.com) have developed a technique that lets standard linear motors 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 let designers reduce the number of motors and electronic drive modules required as well as simplifying overall mechanical design. This results in significantly lower equipment cost by reducing the mass of moving parts, and lets machines run with higher accelerations and operating speeds.

The technology lets horizontally-mounted linear motors 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 allows producing precision magnetically levitated platforms with six axes of controlled motion (3D shifts and tilts) by using ordinary linear motors.

“This innovation in linear motor operation requires no modification to existing motor components,” says Georgo Angelis, Senior Scientist at Philips Applied Technologies. “All you need to do is reposition the components slightly and drive them in an intelligent way.”

How it works

Ironless, multi-phase linear motors rely on the fact that a current-carrying conductor in a magnetic field gets pushed perpendicular to the direction of the current and the direction of the field (the Lorentz force). This latter force 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 2D motion from one motor, Angelis' team shifted the position of the coils with respect to the magnet track so 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 allows producing fully floating, bearing-less platforms, which unlike air-bearing solutions, can be used in vacuum. Angelis says a 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).