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FAQ (Frequently Asked Questions)
Category:
CDS 101/110 Fall 2003
Identifiers: FN H0 H1 H2 H3 H4 H5 H6 H7 H8 L0.0 L1.1 L1.2 L10.1 L2.1 L2.2 L3.1 L3.2 L4.1 L4.2 L5.1 L5.2 L6.2 L8.1 L9.1 L9.2
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In question 1 a, the tracking error does not seem satisifed at DC, so what should I do?
Submitted by: mreiser
Submitted on: November 21, 2003
Identifier:
H7
Instead of showing the maximum freqeuncy for which the closed loop system satisfies the tracking spec., please just show us the frequency range over which tracking occurs with less than 5% error.
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In HW7, problem 2(a), should we generate the Bode plot for the plant of the plant + controller?
Submitted by: waydo
Submitted on: November 23, 2003
Identifier:
H7
For part (a) of this problem, you should generate the Bode plot for the plant P only and draw in the constraints on L (so they will be violated in some places). Then in part (b) you should design a compensator so that L meets the specifications.
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Hints, comments on number 3
Submitted by: mreiser
Submitted on: November 23, 2003
Identifier:
H7
Do I need to use a lead compensator?
for part (a) many of you have been interpreting this problem to mean: keeping the lead compensator, how can I choose K, a, and b to get robust stability and as much performance as possible for the nominal plant. This interpretation is fine, and you will probably not be able to satisfy all 5, but do your best. Alternatively, if you choose to use a higher order controller, this is fine too. You should certainly try a higher order controller for part (b). Adding poles and zeros in sisotool is a nice way to do this.
For part (c), what do I do for the time delay?
Use Pade approxmation, second order is fine.
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In problem 2, how do I come up with open loop constraints based on the third and fourth specifications?
Submitted by: mreiser
Submitted on: November 23, 2003
Identifier:
H7
This can be done, but we have not covered the necessary material in class. If you want to try it, approximate the system as second order and see if you can relate max overshoot and max gain to the phase margin. You should definitely verify that these two conditions are met, by plotting the step response and closed loop bode plot. Keep in mind that the max overshoot is related to relative stability, which is related to phase margin. Just make sure that your phase margin is not too small or else your overshoot will suffer.
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