Developed at NASAÂ’s Marshall Space Flight Center (Huntsville, AL), a micro-commanding rotational-position-control system offers the advantage of less mechanical complexity, susceptibility to mechanical resonances, power demand, bulk, weight, and lower cost, relative to prior rotational-position-control systems based on stepping motors and gear drives. This system includes a digital-signal-processor (DSP)-based electronic controller, plus a shaft-angle resolver and a servomotor mounted on the same shaft.

Heretofore, micro-stepping has usually been associated with stepping motors, but in this system, the servomotor is micro-commanded in response to rotational-position feedback from the shaft-angle resolver.
For more information, see page 32 of the March issue of NASA Tech Briefs, or click here.

Medical scientists at Johns Hopkins University (Baltimore, MD) have constructed the “PneuStep,” a prototype pneumatic step motor that is the first of its kind. The motor was developed as part of a project for a robot that could operate precisely within the closed bore of high-intensity MRI equipment. The pneumatic nature of the step motor was seen as ideal in the magnetic environment of an MRI machine. The motor is constructed of dielectric and nonmagnetic material, using air formotion and light for fiber optic encoding. A robot actualized by PneuStep motors has been completed and is currently under evaluation.
The PneuStep is designed so that the end-to-end motion of the piston with its cylinder is always exact. The step motor is designed to collect small end-to-end motion strokes in rotary motion. An end-of-stroke motion makes a step. The PneuStep prototype has been constructed in two sizes.
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