Hi everyone,

First I need to say that it is not an homework. This is an exercise.

I need to find 2 transfer function from a block diagram, but I can't find answer b). But I know how to go from b) to c).

Here is my problem statement (this is a translation from french):

We want to know position x(t) of mass m with the help of a DC moteur and a gear system. All system elements are shown on picture 2.

a) With the use of block diagram (first picture I posted) and parameters (in my last picture), find transfer function of every system elements. Consider initial condition to zero.

b) Simplify the block diagram found in (a) to obtain the transfer function between the power supply of the motor and the speed of rotation of its shaft.

c) From the transfer functions found in (b), find one that connects the motor electric supply to the displacement of the mass x (t). Determine the order of the system.

And here is 3 picture to help solve my problem:

http://s2.postimg.org/y8ve80duh/motor.png

http://s1.postimg.org/xe4ihw7fz/transferfunction.png

http://s2.postimg.org/y8ve80duh/motor.png

Thank you very much. I have an exam monday!

JP