Non zero initial value second order system simulink

Hi all,

I am simulating a second order system with the transfer function component in simulink.

This component is fed a step signal, with initial value one and step amplitude -1. That is to say the step decreases from 1 to 0 instead of the usual 0 to 1.

The output I get from the transfer function oscillates twice : once at initial time and once at the stepping time.

The second oscillation is exactly what I want. But I don't understand the presence of the first one. It's as if at the initial time, the source signal is not fixed at 1 but stepping from zero to 1 instantly.

How can I force that input source signal to have an actual initial value of one ?

Thank you for your answers.

Answer 1

[Mandar Patwardhan]

Go to the configuration parameters and consider reducing the step size to a smaller value and check if you still see the initial value stepping from zero to 1 instantly.