simscape (planetary gear)

In the planetary gear system,

we have positioned the sun and ring gears at the input, with the carrier gear at the output.

When speed (rpm) is applied as the input, the sum of the sun and ring gear speeds results in an equivalent value at the output.(Ns+Nr=-Nc)

However, when torque is applied as the input and the ratio of NR/NS is not maintained, the value of the carrier does not add up.

The condition where the ring gear's value is twice that of the sun gear, with NR/NS equal to 2, represents a specific ratio at which this occurs.

Why doesn't the added value come out when torque is input?

[Naveed Ahmed]

Thanks for this question.

Answer 1

[Steve Miller]

The planetary gear enforces a kinematic relationship between the input and output shafts. The torque levels, however, will depend on the effective inertia of the entire system (shafts, carrier, etc.). There are situations where the relationship between torques applied and torque measured will require a little more math than simply looking at the ratio of the planetary gear.

The scenario shown below is straightforward and similar to what you describe in your post. However, if you vary the input torque to the sun gear, you will see the output torque change. You would need to look at the kinematic relationships to get a full understanding of what affects the sum of torque at the carrier shaft.

--Steve