Many of today’s precision applications necessitate gears capable of dramatic speed reductions, power densities, and transmission accuracies. Leading choices in these designs include trochoidal and cycloidal gearing as well as gearsets relying on wave-inducing subcomponents having an elliptical or Reuleaux or other polygonal shape.
Recall from geometry that trochoidal and cycloidal gearing includes elements that rotate and trace curves around some other element. More specifically, cycloids traced by a point on a rolling element’s circumference include epicycloids (for which the element rolls along the outside of a sun gear or other reference component) and hypocycloids for which the element rolls within a ring or other reference component. In contrast, trochoids (and their subtypes) are traced not by a point on the rolling element’s circumference but rather some point within or without. One particularly common subtype of epicyclic gearing is planetary gearing.
In the following articles, the editors of Design World explain the variations of (and applications for) these strain-wave and cycloidal gear offerings in high-end machine tool, aerospace, material handling, and robotic applications.