Model of a smooth step signal.
The output ( y ) remains at its initial value yin until time
is equal to tin.
Then the signal changes smoothly. After the smoth start the signal grows up linearly with a slope m.
When the output signal is close to the final value yfin, it is reached smoothly.
The parameter alfa (that has to be coprises between 0 and 1), indicates the portion of the rising
time occupied by the smooth junction.
In this case alfa = 0.1, this indicates that each junction occupy the 10 % of the total rising time.
Fixed Point not available in this model