行星齿轮系
周转轮系
外摆线轮系

[ noun ]
a system of epicyclic gears in which at least one wheel axis itself revolves about another fixed axis
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epicyclic \ep`i*cyc"lic\, epicyclical \ep`i*cyc"lic*al\, a.
Pertaining to, resembling, or having the motion of, an
epicycle.

{Epicyclic train} (Mach.), a train of mechanism in which
epicyclic motion is involved; esp., a train of spur
wheels, bevel wheels, or belt pulleys, in which an arm,
carrying one or more of the wheels, sweeps around a center
lying in an axis common to the other wheels.