Three time-domain parameters often used to describe the step response are rise time, delay time, and overshoot. Rise timeðTRÞ is the time interval required for the step response to rise from 10% to 90% of its steady-state value gð∞Þ. Delay timeðTDÞ is the time interval required for the step response to reach 50% of its steady-state value. Overshoot is the difference between the peak value of the step response and its steadystate value. Overshoot is usually expressed as a percentage of the steady-state value, namely

Figure 11–25 illustrates these descriptors for a typical step response.
Step response descriptors are used to specify the performance of both analog and digital systems. Rise time governs how rapidly the system responds to an abrupt change in the input. Delay time controls the time between the application of an abrupt change and the appearance of a significant change in the output. Overshoot indicates the amount of damping

present in the system. Lightly damped oscillations produce large overshoots and may cause erroneous state changes in digital systems.
Rise time, delay time, and overshoot can be determined experimentally or calculated using modern computer tools. How to use MATLAB to find these parameteres can be found in Web appendix D.

Transcribed Image Text:

Overshoot 8max-8(00) = x100 g(00)