MIT6_003S10_lec13

MIT6_003S10_lec13 - .003 Signals and Systems T Feedback and...

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Unformatted text preview: .003: Signals and Systems T Feedback and Control arch 18, 2010 Feedback and Control Feedback: simple, elegant, and robust framework for control. + − X Y E S C controller plant sensor e started with robotic driving. d i = desiredFront d o = distanceFront Feedback and Control Using feedback to enhance performance. Examples: • improve performance of an op amp circuit. • control position of a motor. • reduce sensitivity to unwanted parameter variation. • reduce distortions. • stabilize unstable systems − magnetic levitation − inverted pendulum Feedback and Control Reducing sensitivity to unwanted parameter variation. Example: power amplifier power amplifier MP3 player F speaker 8 <F < 12 Changes in F (due to changes in temperature, for example) lead to undesired changes in sound level. Feedback and Control Feedback can be used to compensate for parameter variation. power amplifier F MP3 player K β + 8 <F < 12 speaker X Y − KF H ( s ) = 1 + βKF If K is made large, so that βKF 1 , then 1 H ( s ) ≈ β independent of K or F ! Feedback and Control Feedback reduces the change in gain due to change in F . F MP3 player 100 1 10 + 8 <F < 12 X Y − 10 20 8 <F < 12 F Gain to Speaker F (no feedback) 100 F 1 + 100 F 10 (feedback) 10 20 heck Yourself F MP3 player K β + power amplifier 8 <F < 12 speaker X Y − Feedback greatly reduces sensitivity to variations in K or F . lim K →∞ H ( s ) = KF 1 + βKF → 1 β What about variations in β ? Aren’t those important? heck Yourself hat about variations in β ? Aren’t those important? The value of β is typically determined with resistors, whose values are quite stable (compared to semiconductor devices). rossover Distortion Feedback can compensate for parameter variation even when the variation occurs rapidly....
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This note was uploaded on 12/14/2011 for the course EE 6.003 taught by Professor Freeman during the Fall '11 term at MIT.

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MIT6_003S10_lec13 - .003 Signals and Systems T Feedback and...

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