# Viscous drag parallel to the axis of rotation: Control Systems

#### kostoglotov

1. Homework Statement

https://i.imgur.com/WPAKuf4.png

seeking $G(s) = \frac{\theta_2(s)}{\tau(s)}$

2. Homework Equations

3. The Attempt at a Solution

What does it mean when the viscous drag is parallel to the axis of rotation?

It also turns out that this system needs two equations. I can sort of see why, even though it doesn't have two masses, I'm not 100% sure though, how to break this system up into two equations, where and how to make the break.

Any help at all would be very appreciated, thank you :)

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#### Nidum

Gold Member
That is a truly awful diagram .

Nevertheless it is possible to work out what the various bits do if we assume that this is a purely rotary system .

Those damper terms and the energy accumulator term all act in a rotary sense and not in the linear sense depicted . You can infer this anyway from their dimensions - they are all quoted as being per radian .

#### rude man

Homework Helper
Gold Member
1. Homework Statement

View attachment 210469

https://i.imgur.com/WPAKuf4.png

seeking $G(s) = \frac{\theta_2(s)}{\tau(s)}$

2. Homework Equations

3. The Attempt at a Solution

What does it mean when the viscous drag is parallel to the axis of rotation?
poor statement but just assume there is rotational drag torque in those three places.

It also turns out that this system needs two equations. I can sort of see why, even though it doesn't have two masses, I'm not 100% sure though, how to break this system up into two equations, where and how to make the break.
I would label the right-hand side of the rotor θ1, then you can have θ1/τ as the 1st equation and θ21 as the 2nd equation, then multiply the two transfer functions to get θ2/τ.