310202a Intro To Automatic Control Flashcards
List the two types of control strategies
- Feedback control
- Feed forward control
Explain how a feedback control strategy responds to a disturbance
When an error or disturbance occurs in a feedback control strategy, the control system reacts to reduce the magnitude of the error by changing the manipulated variable
How does a feed forward control strategy respond to a disturbance??
In a feedforward control strategy, the disturbances are measured first and then the manipulated variables are changed to keep the controlled variable at its required value.
List 3 reasons for implementing automatic control for an industrial size plant.
Any three of the following are correct
1. Increases economic productivity
2. Improves efficiency in the use of materials and resources
3. Improves product quality
4. Improves safety
5. Reduces labor requirements
6. Reduces pollution
7. Maximizes profitability
Where is this device located?
Located in the field
Where is this device located
Located on front of central or main console
Where is this device located
Located in rear of central or main panel
Where is this device located
Located on front of secondary or local panel console
Where is this device located
Located in rear of secondary or local panel
For a feedback controller that is in manual, explain what effect adjusting the controller’s set point would have on the process.
Adjusting the controller set point has no effect as the control algorithm is not connected to the controller’s output (CO)
State 4 situations when an operator may operate a feedback control loop in manual rather than auto
- During startup or shutdown of a process
- When automatic control is not providing satisfactory control
- When maintenance is being performed on a component of the loop
- During emergency situations
For a feedback controller that is in manual, explain what effect adjusting the controller’s manual output would have on the process
Adjusting the controller manual output changes the signal to the final control element (FCE), which changes the controlled variable (CV)
For a bumpless transfer to occur when switching from manual to auto, what two conditions must be met first?
- The manual control output(CO) must match the controller output(CO) from the controller algorithm
- The set point(SP) must match the process variable(PV)
For a seamless bumpless transfer to occur when switching from auto to manual, what condition must be met?
The manual control output(CO) must match the control output(CO) from the controller algorithm
What is set point tracking?And why would this be programmed into a digital controller?
Set point tracking is when a digital controller is programmed to make the set point(SP) equal to the process variable(PV) when in manual, since the error is 0, the control algorithm does not calculate any change in its output value when the controller is switched to auto
What type of signal does this symbol represent
Instrument connections to process and equipment, process impulse lines and analyze sample lines
What type of signal does this symbol represent
Electronic or electrical signal continuously variable or binary, function diagram binary signal
What type of signal does this symbol represent
Pneumatic signal continuously variable or binary
What type of signal does this symbol represent
Communication link or bus connecting two or more independent micro processor or computer-based systems.
What type of signal does this symbol represent
Filled thermal element capillary tube filled sensing line between pressure seal and instrument.
What type of signal does this symbol represent
Hydraulic signal
What is a direct acting controller?
A controller is direct acting if its output, which is the controller output (CO) increases in response to an increasing measured signal (PV)
What is a reverse acting controller?
A controller is reverse acting if its output (CO) decreases in response to an increasing measured signal (PV)
What is a direct acting final control element? (FCE)
The final control element (FCE) is direct acting if an increase in controller output (CO) causes an increase in the output flow (f)
What is a reverse acting final control element?
The final control element (FCE) is reverse acting if an increasing input signal (CO) causes a decrease in the output flow (f)
What is a direct acting transmitter?
A transmitter is direct acting when an increasing input signal causes an increase in its output signal
What is a reverse acting transmitter?
A transmitter is reverse acting when an increasing input signal causes a decrease in its output signal
What is a direct acting process?
The process is direct acting when increasing input (f) causes an increase in the output (CV)
What is a reverse acting process?
The process is reverse acting when an increasing input (f) causes a decrease in the output (CV)
If the combination of the final control element (FCE), the process and transmitter are positive, what must controller be? Directing acting or reverse acting?
A controller must be reverse acting when the combination of the final control element, the process and the transmitter are positive
If the combination of the final control element (FCE), the process and transmitter are negative, what must controller be? Directing acting or reverse acting?
The controller must be direct acting if the combination of the final control element, the process and the transmitter is negative.
A direct acting controller receives a process variable (PV) signal of 80%
The set point (SP) of the controller is 85%
What is the controller error produced?
-5%
A reverse acting controller with a set point (SP) of 35% receives a process variable (PV) of 50%
What is the controller error produced?
-15%
A direct acting controller with a set point (SP) of 60% receives a process variable (PV) of 70%
What is the controller error produced?
10%
A controller installed in a loop is set to manual.
This means the loop is closed
True or false?
False
What 4 components are required to make up a control loop?
- Controller
- Process being controlled
- Measuring element
- Final control element
