Step and Impulse Response of a Second-Order System

Consider a second-order process, where the transfer function is given by , where is the process time constant and is the damping coefficient.

This Demonstration shows the response of this process when subject to a step input of amplitude (i.e., , where is the unit step function) or an impulse input of amplitude (i.e., , where is the Dirac delta function). The response is obtained by Laplace inversion using the Mathematica built-in function, InverseLaplaceTransform.

When , one gets an underdamped response with oscillatory behavior. Critically damped and overdamped systems result when and , respectively. For these last two cases, the response does not exhibit oscillations. A critically damped response returns to steady state faster than an overdamped response when the system is subject to an impulse input.