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What does Kc do?

What does Kc do?. What is Kc?. Kc is the Controller Gain of a control system. It can be adjusted to obtain a variety of system responses. Feedback Control. E(t): Input to the Controller. E(t)=R(t)-C(t). E(t) = Error of system R(t) = Set Point C(t) = Output of System (Controlled Variable).

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What does Kc do?

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  1. What does Kc do?

  2. What is Kc? • Kc is the Controller Gain of a control system. • It can be adjusted to obtain a variety of system responses.

  3. Feedback Control

  4. E(t): Input to the Controller E(t)=R(t)-C(t) • E(t) = Error of system • R(t) = Set Point • C(t) = Output of System (Controlled Variable)

  5. Relationship • E(t) is directly related to Kc because Kc adjusts the system’s input to reduce E(t). • In a proportional controller by the equation • The controlled output will always have an offset from the set point after a change of set point. • The offset is the difference between the output and the setpoint

  6. Offset • E(s) = R(s)-C(s) • By Block diagram algebra: By FVT for R(s) = 1/s (step response) E(s) is never zero unless Kc is infinity. There is always offset.

  7. Controller Operating Lines KAC 4-9-04 Offset 1 Kc D Rs Rs SSOC

  8. KQD KCU KCD

  9. Effects of Kc Kc = 24 %/cm H20 Decay Ratio=1/500

  10. Effects of Kc Kc = 48 %/cm H20 Decay Ratio=1/10

  11. Effects of Kc Kc = 67 %/cm H20 Decay Ratio=1/4

  12. As Kc Increases • The Decay Ratio increases • The frequency increases • The offset decreases • The settling time increases

  13. What does Kc Do? • Kc effects the Decay Ratio, Frequency, Settling time, Offset. • As the Kc of a system increases so does the oscillation amplitude and frequency of the system output. • There is an optimum value of Kc that minimizes offset while minimizing oscillation.

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