1. List any four objectives of process control.?
Suppressing the influence of external disturbances, Optimizing the performance, Increasing the Productivity, Cost effective
2. Define process?
Any system comprised of dynamic variables usually involved in manufacturing and production operations. It is defines as a series of operations during which some materials are placed in more useful state.
3. What is manipulated variable?
It is a variable which is altered by the automatic control equipment so as to change the variable under and make it conform with the desired value.
4. Define Controlled variable?
It is the quantity of control system which is directly measured and controlled.
5. What do you mean by self regulation?
The output will move from one steady state to another for the sustained change in input. This means that for change in some input variable the output variable will rise until it reaches a steady state (inflow = outflow). It is the tendency of the process to adopt a specific value of controlled variable for nominal load with no control operations.
6. Why do we need mathematical modeling of process?
The physical equipment of the chemical process we want to control have not been constructed. Consequently we cannot experiment to determine how the process reacts to various inputs and therefore we cannot design the appropr iate control system. If the process equipment needs to be available for experimentation the procedure is costly. Therefore we need a simple description of how the process reacts to various inputs, and this is what the mathematical models can provide to the control designer.
7. Name different test inputs?
Step, Ramp, Impulse, Sinusoidal, Pulse inputs
8. Name a process giving inverse response?
Drum boiler system, in which the flow rate of the cold feed water is increased by a step the total volume of the boiling water and consequently the liquid level will decreased for a short period and then it will start increasing.
9. Define interacting system and give an example?
Load changes in first process affects the second process and vise versa when both are connected in series nature is called interacting system. Eg. Two level tanks are connected in series.
10. What is meant by non-self regulation?
A system that grows without limit for a sustained change in input (constant outflow or outflow independent of inflow condition).
11. Write any two characteristics of first order process modeling?
The smaller the value of time constant the steeper the initial response of the system. A first order lag proce ss is self regulating the ultimate value of the response equal to Kp (steady state gain of the process) for a unit step change in the input.
12. Distinguish between continuous process and batch process?
A process in which the materials or work flows more or less continuously through a plant apparatus while being treated is termed as continuous process. The problem of continuous process is due to load changes. (e.g.) storage vessel control. A process in which the materials or work are stationary at one physical location while being treated is termed as batch process. (e.g.) furnace.
13. Explain the function of controller?
The element in a process control loop that evaluated error of the controlled variable and initiates corrective action by a signal to the controlling variable.
14. What is the purpose of final control element?
Components of a control system (such as valve) is used to directly regulates the flow of energy or materials to the process. It directly determines the value of manipulated variable.
15. Define Process control?
It is the scheme that describes how much the manipulated variable should change inorder to bring the controlled variable back to the setpoint.
16. List the two types of process control?
i) Direct process control – Controlled variable directly indicates the performance of the process
Eg. Water heater system
ii) In Direct Process control the performance of the process. – Controlled variable indirectly indicates
Eg. Annealing
17. What is Servo operation and Regulatory operation?
If the purpose of the control system is to make the process follow the changes in setpoint as quick as possible, then it is servo operation.
18. What is mathematical modeling?
Set of equations that characterize the process is termed as Mathematical Modelling.
19. Define an non-interacting system?
The dynamic behaviour one tank is affected by the other, but the reverse is not true, then it is noninteracting system. Here the liquid heads are independent of each other.
20. Define an interacting system?
The dynamic behavior one tank is affected by the other, but the reverse is also true, then it is noninteracting system. Here the liquid heads are dependent of each other.
21. Mention two drawbacks of derivative action?
(i) The output of controller is zero at constant error condition.
(ii)It will amplify the noise present in the error signal.
22. What are the steps involved to design a best controller?
Define appropriate performance criterion (ISE, IAE, ITATE). Compute the value of the performance
criterion using a P, PI, or PID controller with the best setting for the adjusted parameters Kp, Ti, Td. Select controller which give the best value for the performance criterion.
23. Define proportional control mode?
A controller mode in which the controller output is directly proportional to the error signal
P=Kpep+p0
Where
P-controller output
Kp= Propotional gain,
ep=error in percent of variable range,
P0- Bias.
24. Define proportional band?
Proportional band is def ined as the change in input of proportional controller mode required to produce a full-scale change in output
25. Define offset?
It is the steady state deviation (error) resulting from a change in value of load variable.
26. Define error (deviation)?
It is the difference at any instant between the value of controlled variable and the set point. E=S.PP.V
27. Why is the electronic controller preferred to pneumatic controller?
Electronic signals operate over great distance without time lags. Electronic signals can be made compatible with digital controllers. Electronic devices can be designed to be essentially maintenance free. Intrinsic safety techniques eliminate electrical hazards. Less expensive to install. More energy efficient. Due to the above said properties electronic controllers are preferred to pneumatic controller.
28. Explain the function of controller.?
The element in process control loop that evaluates error of the controlled variable and initiates corrective action by a signal to the controlling variable.
29. Write any two limitations of single speed floating control.?
The present output depends on the time history of errors and such history is not known, the actual value of controller output floats at an undetermined value. If the deviation persists controller saturates at either 100% or 0% and remain there until an error drives it towards opposite extreme.
Suppressing the influence of external disturbances, Optimizing the performance, Increasing the Productivity, Cost effective
2. Define process?
Any system comprised of dynamic variables usually involved in manufacturing and production operations. It is defines as a series of operations during which some materials are placed in more useful state.
3. What is manipulated variable?
It is a variable which is altered by the automatic control equipment so as to change the variable under and make it conform with the desired value.
4. Define Controlled variable?
It is the quantity of control system which is directly measured and controlled.
5. What do you mean by self regulation?
The output will move from one steady state to another for the sustained change in input. This means that for change in some input variable the output variable will rise until it reaches a steady state (inflow = outflow). It is the tendency of the process to adopt a specific value of controlled variable for nominal load with no control operations.
6. Why do we need mathematical modeling of process?
The physical equipment of the chemical process we want to control have not been constructed. Consequently we cannot experiment to determine how the process reacts to various inputs and therefore we cannot design the appropr iate control system. If the process equipment needs to be available for experimentation the procedure is costly. Therefore we need a simple description of how the process reacts to various inputs, and this is what the mathematical models can provide to the control designer.
7. Name different test inputs?
Step, Ramp, Impulse, Sinusoidal, Pulse inputs
8. Name a process giving inverse response?
Drum boiler system, in which the flow rate of the cold feed water is increased by a step the total volume of the boiling water and consequently the liquid level will decreased for a short period and then it will start increasing.
9. Define interacting system and give an example?
Load changes in first process affects the second process and vise versa when both are connected in series nature is called interacting system. Eg. Two level tanks are connected in series.
10. What is meant by non-self regulation?
A system that grows without limit for a sustained change in input (constant outflow or outflow independent of inflow condition).
11. Write any two characteristics of first order process modeling?
The smaller the value of time constant the steeper the initial response of the system. A first order lag proce ss is self regulating the ultimate value of the response equal to Kp (steady state gain of the process) for a unit step change in the input.
12. Distinguish between continuous process and batch process?
A process in which the materials or work flows more or less continuously through a plant apparatus while being treated is termed as continuous process. The problem of continuous process is due to load changes. (e.g.) storage vessel control. A process in which the materials or work are stationary at one physical location while being treated is termed as batch process. (e.g.) furnace.
13. Explain the function of controller?
The element in a process control loop that evaluated error of the controlled variable and initiates corrective action by a signal to the controlling variable.
14. What is the purpose of final control element?
Components of a control system (such as valve) is used to directly regulates the flow of energy or materials to the process. It directly determines the value of manipulated variable.
15. Define Process control?
It is the scheme that describes how much the manipulated variable should change inorder to bring the controlled variable back to the setpoint.
16. List the two types of process control?
i) Direct process control – Controlled variable directly indicates the performance of the process
Eg. Water heater system
ii) In Direct Process control the performance of the process. – Controlled variable indirectly indicates
Eg. Annealing
17. What is Servo operation and Regulatory operation?
If the purpose of the control system is to make the process follow the changes in setpoint as quick as possible, then it is servo operation.
18. What is mathematical modeling?
Set of equations that characterize the process is termed as Mathematical Modelling.
19. Define an non-interacting system?
The dynamic behaviour one tank is affected by the other, but the reverse is not true, then it is noninteracting system. Here the liquid heads are independent of each other.
20. Define an interacting system?
The dynamic behavior one tank is affected by the other, but the reverse is also true, then it is noninteracting system. Here the liquid heads are dependent of each other.
21. Mention two drawbacks of derivative action?
(i) The output of controller is zero at constant error condition.
(ii)It will amplify the noise present in the error signal.
22. What are the steps involved to design a best controller?
Define appropriate performance criterion (ISE, IAE, ITATE). Compute the value of the performance
criterion using a P, PI, or PID controller with the best setting for the adjusted parameters Kp, Ti, Td. Select controller which give the best value for the performance criterion.
23. Define proportional control mode?
A controller mode in which the controller output is directly proportional to the error signal
P=Kpep+p0
Where
P-controller output
Kp= Propotional gain,
ep=error in percent of variable range,
P0- Bias.
24. Define proportional band?
Proportional band is def ined as the change in input of proportional controller mode required to produce a full-scale change in output
25. Define offset?
It is the steady state deviation (error) resulting from a change in value of load variable.
26. Define error (deviation)?
It is the difference at any instant between the value of controlled variable and the set point. E=S.PP.V
27. Why is the electronic controller preferred to pneumatic controller?
Electronic signals operate over great distance without time lags. Electronic signals can be made compatible with digital controllers. Electronic devices can be designed to be essentially maintenance free. Intrinsic safety techniques eliminate electrical hazards. Less expensive to install. More energy efficient. Due to the above said properties electronic controllers are preferred to pneumatic controller.
28. Explain the function of controller.?
The element in process control loop that evaluates error of the controlled variable and initiates corrective action by a signal to the controlling variable.
29. Write any two limitations of single speed floating control.?
The present output depends on the time history of errors and such history is not known, the actual value of controller output floats at an undetermined value. If the deviation persists controller saturates at either 100% or 0% and remain there until an error drives it towards opposite extreme.
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