Chapter 7: System Time Response Characteristics. In this chapter:. W e investigate the time response of a sampled data system and compare it with the response of a similar continuous system.
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System Time Response Characteristics
The time response of both discrete-time system and its continuous-time equivalent are shown.
where ωnis the undamped natural frequency of the system and ζ is the damping ratio of the system.
When a second-order system is excited with a unit step input, the typical output response is as shown in Figure 7.3. Based on this figure, the following performance parameters are usually defined: maximum overshoot; peak time; rise time; settling time; and steady-state error.
Let s = σ + jωdescribes a point in the s-plane. Then, this point is mapped into z-plane as
If ω is kept constant and σ is increased in the left-hand s-plane, the pole locations in the z-plane move towards the origin, away from the unit circle.
As shown in Figure 7.6, lines of constant σ in the s-plane are mapped into circles in the z-plane with radius eσT. If the line is on the left-hand side of the s-plane then the radius of the circle in the z-plane is less than 1. If on the other hand the line is on the right-hand side of the s-plane then the radius of the circle in the z-plane is greater than 1.