MECH466 - Lecture19-FrequencyDomainSpecifications-2009W

15 200809 transient overshoot mech466 automatic

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Unformatted text preview: xample Percent overshoot For small percent overshoot, L should have larger phase margin. For illustration, we use the feedback system: For 20 C(s) C(s) G(s) G(s) Controller 1.8 OL Bode plot CL step response 1.6 Plant 0 1.4 1.2 -20 -1 10 0 1 10 10 1 -100 0.8 -120 0.6 -140 0.4 -160 -180 -1 10 2008/09 MECH466 : Automatic Control 17 0 1 10 2008/09 Typical desired OL Bode plot Steady-state accuracy SteadySensitivity Disturbance rejection 0.2 PM 10 0 0 5 Response speed For fast response, L should have larger gain crossover frequency. Transient Response speed Noise reduction 20 1.4 OL Bode plot Relative stability CL step response 0 1 Noise reduction -20 0.8 0 10 0.6 -100 Transient Overshoot -120 0.4 -140 0.2 -160 -180 -1 10 2008/09 15 18 1.2 Relative stability 10 MECH466 : Automatic Control MECH466 : Automatic Control 19 2008/09 0 10 1 10 0 0 MECH466 : Automatic Control 5 10 15 20 5 Typical desired OL Bode plot Steady-state accuracy SteadySensitivity Disturbance rejection Relative stability We require adequate GM and PM for: We safety against inaccuracies in modeling safety reasonable transient response (overshoot) reasonable Transient Response speed Noise reduction Relative stability Noise reduction Transient Overshoot Relative stability 2008/09 It is difficult to give reasonable numbers of GM It and PM for general cases, but usually, GM should be at least 6dB GM PM should be at least 45deg PM (These values are not absolute but approximate!) In controller design, we are espe...
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This document was uploaded on 03/05/2014 for the course MECH 466 at University of British Columbia.

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