Open loop transfer function this circuit

Hello, Could you please help me get the Modeling of this circuit I'm so weak at modeling and i want to Try Pid on it afterward.

[M]

What kind of model are you using ? What are your inputs ? outputs ?

[Zack El]

My input is the Variable resistor and the output is the motor when i change the value of the resistor the motor speed changes.

[M]

And what is the relationship between these two variables ? To simulate (and control) your system, you should be able to represent it with an equation.

[Zack El]

That is what I need the equation. So let's assume that the output is V and it's equal to the volt in the fixed resistor so the output is the Fixed resistor.

Answer 1

[Birdman]

I prepared a model. What I basically did is modelling the voltage divider part of yours with a MATLAB Function(please see the content of it in model) and DC motor part with Transfer Fcn blocks. I set the both resistors to be changeable during the simulation(gave them as inputs to the function) and by a slider parameter, you can also change the weight of the variable resistor during simulation and instantly see the results on Scope. Change this model according to your needs and I believe it will be easy to implement PID on it afterwards. Note that I set the simulation time to Inf so that you can easily observe what happens to the speed of the motor when you change the resistor's value by its parameter.

Hope this helps.

[Zack El]

Thanks a lot I will try this.