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Represent set of carrier, planet, and ring gear wheels with specified ring-planet gear ratio




The Ring-Planet gear block represents a set of carrier, planet, and ring gear wheels. The planet is connected to and rotates with respect to the carrier. The planet and ring corotate with a fixed gear ratio that you specify and in the same direction with respect to the carrier. A ring-planet gear is, along with a planet-planet gear, a basic element of a planetary gear set.

Axis Motions and Constraints

The Ring-Planet block imposes one kinematic and one geometric constraint on the three connected axes:

rRωR = rCωC + rPωP , rR = rC + rP

In terms of the ring-to-planet gear ratio gRP = rR/rP, the effective kinematic constraint is

gRP·ωR = ωP + (gRP – 1)ωC ,

reducing the three axes to two independent degrees of freedom.

The gear ratio is also the ratio of the number of teeth on each gear and the ratio of the torques in each axis, gRP= NR/NP = τRP.

    Warning:   All gear ratios must be strictly positive. If any gear ratio equals 0 or becomes negative at any time, a Simscape™ Driveline™ simulation stops with an error.

    The ring-planet gear ratio gRP must be strictly greater than one.

Ring-Planet Gear Set

Dialog Box and Parameters

Ring (R)/Planet (P) gear ratio

Ratio gRP of the ring gear wheel radius to the planet gear wheel radius. This gear ratio must be strictly greater than 1. The default value is 2.


The drive_ring_planet_pic example illustrates the ring-planet gear with an animation.

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