Instantaneous DC output using Laplace transform

I am testing a feedback system in which a feedback signal from sensor is applied to a correction network and then compared with threshold values.

I need some clue on how to get around this task, I will be applying DC voltage to the network and will compare its output obtained with the one I calculated theoretically. Here is the transfer function of the network with a natural frequency of 90Hz

$$H(s)=\dfrac{1+0.145s+0.0019s^2}{1+\dfrac{0.8}{150 }s+\dfrac{1}{150²}s²}×\dfrac{1}{1+0.0012s}×\dfrac{1}{1+0.008s}$$

I calculated the output of the network by finding its inverse Laplace with step function as its input. The issue is that the output voltage obtained from solving this is a non-linear function hence changes it at every instant so how am I supposed to test the output for a particular DC input?

Any ideas?

Here is the step response I plotted using Matlab