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Measurement and Process Theory > Chapter 37 > Flashcards

Chapter 37 Flashcards

1
Q

What is controller tuning?
Controller tuning is the____ determining the tuning _______ for the PID controller _______ gain, ________time, and _______ time to obtain a desired controller response to process disturbances.

A

What is controller tuning?
Controller tuning is the__process__ determining the tuning _____coefficients___ for the PID controller ______proportional_ gain, _____integral___time, and _______derivative_ time to obtain a desired controller response to process disturbances.

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2
Q

What are common concerns with controller tuning?
1._______ the______ tuning
coefficients,
2._______ appropriate ________standards.
3. Using _______ controller
4. ______a _______ tuning method.

A

Common concerns with controller tuning are
1.Selecting the proper tuning
coefficients,
2.Developing appropriate performance standards.
3. Using self-tuning controller
4. Choosing a manual tuning method.

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3
Q

What is the symbol for controller gain?

A

(Kc)

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4
Q

What is the symbol for Proportional gain?

A

(Kp)

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5
Q

What is the symbol forProportional Band?

A

(PB)

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6
Q

What is the symbol for Reset Rate?

A

(T1)

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7
Q

What is the symbol for Reset Gain?

A

(R1)

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8
Q

What is the symbol for Reset Gain?

A

(K1)

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9
Q

What is the symbol for Derivative Time?

A

(TD)

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10
Q

What is the symbol for Derivative gain?

A

(KD)

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11
Q

What are performance standards?

Performance Standards are a way of measuring the effectiveness of controller tuning and controller action.

A

Performance Standards are a way of measuring the effectiveness of controller tuning and controller action.

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12
Q

What is a Performance Standard defined as?

A

A closed loop response of a second-order system.

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13
Q

What are the three common controller Performance Standards?

A
  1. Decay Ratio
  2. Overshoot
  3. Dead Time
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14
Q

Explain Decay Ratio

A

Decay Ratio-
Is a measurement of how quickly an overshoot decays from one oscillation to the next as the controller brings the process to the setpoint.

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15
Q

What is the most common Decay Ratio Performance Standard?

A

The One-Quarter Decay Ratio

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16
Q

Explain One-quarter decay ratio.

A

One-Quarter Decay Ratio-
Is a response where the amount of overshoot decays to one-fourth of the previous amplitude of the overshoot every whole cycle after being upset by a disturbance.

17
Q

Why is the one-quarter decay ratio so popular?

A

It is very easy to judge when it is obtained.

18
Q

Explain overshoot

A

Overshoot-
Is the change of a process variable (PV) that exeeds the upper dead band value when there is a disturbance to the system.

19
Q

Define Dead Time.

A

Dead Time-
Is the period of time that occurs between the time a change is made to a process and the time the first response to that change is detected.

20
Q

Explain Rise Time.

A

Rise Time-

The length of time required for a PV to cross the ultimate value after a step input change, such as the setpoint change.

21
Q

Explain Dynamic Response Time.

A

Dynamic Response Time-

The length of time required for a PV to remain within 5% of its ultimate value following a step input change.

22
Q

Explain Gain Margin.

A

Gain Margin-
The factor by which controller gain may be increased before instability occurs and therefore is a measure of relative stability.

23
Q

Explain Self-tuning Controller.

A

Self-tuning Controller-
A controller that has built-in algorithms or pattern recognition techniques that periodically test the process and make changes to the controller tuning settings while the process is operating.

24
Q

Explain Stand-alone Controller.

A

Stand-alone Controller-
A controller that has its powers supplies, input signal processing, controller functions, input signals, and displays contained in the same case.

25
Q

What are the three pretuning checks that must be made to a control loop prior to placing it in operation.
1.
2.
3.

A
  1. First ensure that the controller action, direct or reverse, is selected correctly.
  2. Second, determine which controller functions are needed for the process.
  3. Third, determine the initial tuning values that are to be used for the chosen controller functions.
26
Q

Explain the Setpoint Step Change Method.

A

Setpoint Step Change Method-

A manual tuning method that consists of making small changes in the setpoint and observing the responses.

27
Q

What are the six steps to tune a controller with the Setpoint Step Change Method?

A
  1. The controller must be in auto mode and the measurement should be steady.
  2. Start by adjusting the proportional gain.
  3. Repeat step 2 until the controller response is satisfactory.
  4. At this point integral time can be adjusted.
  5. Repeat step 4 until the controller is satisfactory.
  6. If a derivative function is needed in the controller, we it to a value in minutes no larger that the integral time.
28
Q

Explain the Tuning Map Method.

A

Tuning Map Method-

A procedure that compares process curves to one of numerous typical closed loop[ response curves.

29
Q

What are the advantages and disadvantages of the

Tuning Map Method?

A

The advantage of this method is that all the controller parameters can be adjusted at the same time.

The disadvantage of this method is that it can be very difficult to match the present controller response to the correct response on the tuning maps.

30
Q

What is the most common tuning methods?

A

The most common tuning methods are the

  1. Zieglar-Nichols open-loop tuning method or the 2.process reaction curve method and the
  2. Zieglar-Nichols closed-loop tuning method or ultimate period method.

Both methods make changes to the process and measure process parameters related to how the system responds to the changes.

31
Q

Explain Zieglar-Nichols Closed-loop Tuning.

A

Zieglar-Nichols Closed-loop Tuning-

A method of tuning a controller by increasing the gain until the system cycles at the point of instability.

32
Q

What is Ultimate Gain?

A

Ultimate Gain-

Is a closed loop proportional gain at the point of oscillation.

33
Q

What is Ultimate Period?

A

Ultimate Period-

The closed-loop cycle time at the point of oscillation.

34
Q

Explain Zieglar-Nichols Open-loop Tuning

A

Zieglar-Nichols Open-loop Tuning-

A method of tuning a controller based on open loop response to a step input.

35
Q

What is an advantage of Zieglar-Nichols Open-loop Tuning?

A

An advantage of this method is that it is safer than the closed loop method because it does not force the process into oscillation.

36
Q

What is an disadvantage of Zieglar-Nichols Open-loop Tuning?

A

A disadvantage is that it is sometimes difficult to identify all the key parameters with enough accuracy to establish the correct tuning values.

Measurement and Process Theory (5 decks)

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