Medical Device Link .

Medical Technology on the Move Low-inertia motors and integrated motion control systems enhance medical and diagnostic devices. How difficult is it to achieve short-distance moves in high-accuracy motor-driven applications? �It�s not difficult at all,� says Dean Crumlish, senior applications engineer at (Canton, MA, USA), �provided, of course, that time is not an issue.� Stepping in rapid succession through a sequence of precise x and y coordinates only a few centimeters apart becomes increasingly difficult as speed and precision demands rise. Positioning tasks in biomedical applications are especially challenging. Travel is scaled down to millimeters, accuracy tightened to microns, and positioning time is counted in milliseconds. Traditional instruments for positioning slides, test tubes, and microarrays have depended on leadscrew mechanisms. �Today�s demand for higher throughput�which translates into higher acceleration, speed, and accuracy�has run into mechanical limitations,� says Crumlish. Friction and rotational inertia slow down the process at the expense of both accuracy and cost. Enter Copley�s direct-drive Micro Linear motors, which reportedly achieve fast throughput and high reliability in a low-cost package. Their design is very simple. It consists of two basic parts, the thrust rod and the forcer. The thrust rod contains high-intensity permanent magnets. The load-carrying forcer is supported by low-friction bearings and incorporates electrical drive coils in a lightweight polymer. The forcer surrounds the thrust rod, and is propelled along the thrust rod�s length by digitally controlled magnetic fields. Tools for holding slides and test tubes are mounted directly onto the forcer. The motor�s tubular design features a 0.016-in. symmetrical air gap between the fixed and moving components. This gap introduces a very significant application benefit: it obviates the need for exact alignment between the forcer and the thrust rod. By relaxing the force/rod concentricity specifications, the gap simplifies the motor�s integration into high-performance positioning stages. Sinusoidal coil excitation