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Unformatted text preview: 37 NYQUIST PLOT 140 37 Nyquist Plot Consider the attached images; here are a few notes. In the plant impulse response, the initial condition before the impulse is zero. The frequency scale in the transfer function magnitude plots is 10 − 3 − 10 4 radians per second. In the plot of P ( s ) loci, the paths taken approach the origin from ± 90 ◦ , and do not come close to the critical point at − 1+0 j , which is shown with an x . In the plot of P ( s ) C ( s ) loci, the unit circle and some thirty-degree lines are shown with dots. Also, the two paths in this plot connect off the page in the right-half plane. Answer the following questions by circling the correct answer. 1. The overshoot evident in the open-loop plant is about (a) 120% (b) there is no overshoot since this is not a step response (c) 70 % (d) 40% 2. The natural frequency in the open-loop plant is about (a) one Hertz (b) one radian per second- To compute this, you need a whole cycle. (c) 1.2 radians per second (d) six radians per second 3. Based on the plant behavior, P ( s ) probably has (a) no zeros and one pole (b) one zero and one pole (c) no zeros and two poles (d) one zero and two...
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- Spring '05
- Nyquist plot, Imag, downward gain margin, ±90◦