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Electrical engineers - some guidance?

  • 31-10-2017 12:28AM
    #1
    thepikminman
    Registered Users, Registered Users 2 Posts: 178 ✭✭


    Hey guys,

    I have an assignment due in a few days and I'm lost about what is even being asked, even after attending all lectures and studying (or trying to) for hours upon hours.

    If someone could give me some advice on where to start or a simple way to do this assignment that would be very helpful. I've tried everything by myself so far and got bascially nowhere. Thanks!

    Here's the question, it's quite a handful of work, but just some pointers on how to approach would be great! (or more would be greater :)):


    __________________________________________________________________________________________________________________________________________________________________


    Measured results of the open-loop frequency response of a position control system used in a CD read head are given in Table 2.

    Table 2 (those aren't absolute signs around the values, they're my attempt at making a table...the only absolute sign is around the Gₚ(jω) row:
    _________________________________________
    |ω (rad/s): __| 0.12 | 0.40 | 0.80 | 1.8 | 4.0|
    ||Gₚ(jω)| (dB):. |18.3 _| 7.9__|_ 1.8 | –6.2|–18.1|
    |∠Gₚ(jω) (°): __ |−93_ |−100_ |−111|−139 |−181    |

    (a) Plot the results of Table 2 on a Nichols chart, and determine the gain margin and phase margin.

    (b) Due to a need for increased accuracy, it was necessary to introduce a component of P+I control, Gc(s) = (1 + 0.5/s). Calculate how this changes the open-loop frequency response data of Table 2 at frequency values 0.4, 0.8 and 1.8 rad/s.

    (c) Plot the new open-loop frequency response values of part (b) on the same Nichols chart as part (a) and use your results to determine values for the system damping factor, ξ, and undamped natural frequency, ωn.

    (d) Discuss how is the stability of the system is changed by the introduction of the P+I controller in terms of gain margin, phase margin and percentage step response overshoot.

    __________________________________________________________________________________________________________________________________________________________________


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