The torque of a Brushed DC motor is proportional with the current passing through the armatures, so I want to control that current with PWM as to achieve a desired torque.

But how exactly do you control that current? I found out the transfer function I(s)/V(s); a simulation in Matlab (with a step as the input) shows an oscillating response for a while, but eventually settles at 0

So how do you do it?

 

Use an integrator (low-pass filter) to average the current over time.