This tool plots the step response of a system having a transfer function of the form (n₁s + n₂) / (s² + d₁s + d₂)

Download

.xls file (97 KB) or .zip file (27 KB)

How to use the tool

The use of this tool is quite straightforward, simply key in the values of n₁ and n₂  into the cells B8 and B9 and those of d₁ and d₂ into cells B11 and B12. Key in the maximum time in the cell B16, this sets the range of the X-axis of the chart. The step response is shown on the chart.

For example, lets take the first order transfer function 6/(1 + 3s). To plot the step response using this tool, we first note that we need a term with s² in the denominator, and with a coefficient of 1. To get this, we multiply all the terms in the numerator and denominator with s/3.

Thus, 6/(1 + 3s) = 2s / (s² + s/3)

Accordingly, we have
n₁ =2
n₂ = 0
d₁ = 1/3
d₂ = 0

See this screenshot showing the correct entries and the response to a step input from t = 0 to t = 20.