Controls Last Quiz

Question 1

Ziegler-Nichols Pros

Answer 1

• Fast
• Simple
• No model needed

Question 2

Ziegler-Nichols Cons

Answer 2

• Requires large oscillations in MV and CV
• Hard to tell between sustained oscillation and unstable

Question 3

Cianone - Marlin Pros

Answer 3

-Fast
- Simple
- Individual parameters

Question 4

Cianone - Marlin Cons

Answer 4

• Needs FOPDT model

Question 5

Cohen - Coon needs:

Answer 5

• FOPDT
• minimum ISE
• QAD

Question 6

Direct Acting Actuator + Positive Gain = ??

Answer 6

Reverse Acting PID

Question 7

Direct Acting Actuator + Negative Gain = ??

Answer 7

Direct Acting PID

Question 8

Reverse Acting Actuator + Positive Gain = ??

Answer 8

Direct Acting PID

Question 9

Reverse Acting Actuator + Negative Gain = ??

Answer 9

Reverse Acting PID

Question 10

What tuning method is best for a fast responding loop (<10 min)?

Answer 10

Field Tuning

Question 11

What tuning method is best for a slow responding loop (>10 min)?

Answer 11

ATV Tuning

Question 12

What is Filtering good for?

Answer 12

Useful for D action and strong P action

Question 13

Filtering Pros

Answer 13

• memory efficient
• simple

Question 14

Filtering Cons

Answer 14

• doesn’t reject outliers
• doesn’t reject certain frequencies

Question 15

Which of the following: IAE, ITAE, ISE, ITSE, penalize large error?

Answer 15

ISE and ITSE

Question 16

What are the steps to field tuning?

Answer 16

1. Turn off D action and I action
2. Estimate Kc = 1/2Kp
3. Increase Kc until criteria is met
4. For PI, decrease Kc by 10%
5. Estimate Tau-I = 5 Tau-P
6. Decrease Tau-I until criteria is met

Question 17

How do Kc, Tau-I, and Tau-D change as controller aggressiveness increases?

Answer 17

Kc increase, Tau-I decreases, and Tau-D increases

Question 18

What happens to the dynamics as controller aggressiveness increases?

Answer 18

Overdamped -> critically damped -> decaying oscillations -> sustained oscillations -> unstable

Question 19

When do you want P-only control?

Answer 19

For a fast responding system that is naturally integrating
i.e. level and pressure

Question 20

When do you want PI control?

Answer 20

For a non-sluggish system that requires no offset
i.e. flow, temp, pressure, comp

Question 21

When do you want PID control?

Answer 21

For a sluggish system that requires no offset
Needs a low noise sensor
i.e. temp and comp

Question 22

What is bias?

Answer 22

Bias is the initial value sent to the actuator when the PID controller is turned on

Question 23

ATV tuning method pros

Answer 23

• Relatively fast
• Does not upset the system
• Automatic