process control loops and wireless instrumentation

Question 1

Start with closed-loop system with a proportional controller.

Answer 1

Ziegler-Nichols Tuning Method

Question 2

4 steps of Ziegler-Nichols Tuning Method

Answer 2

1. Begin with a low value of gain, Kp
2. Reduce the integrator and derivative gains to 0
3. Increase Kp from 0 to some critical value Kp = Kcr at which sustained oscillations occur. If it does not occur then another method has to be applied.
4. Note that the value Kcr and the corresponding period of sustained oscillation, Pcr sustained oscillation with period Pcr. (Pcr is measured in sec.)

Question 3

state the table of Ziegler-Nichols Tuning Method

Question 4

Advantages of Ziegler-Nichols Tuning

Answer 4

1. It does not require expert knowledge.
2. It does not require model / simulation of system.
3. Often produces good initial Kp,Ki,Kd.

Question 5

Disadvantages of Ziegler-Nichols Tuning

Answer 5

1. It is not mathematically rigorous.
2. Requires a stable system.
3. If you do not have a model / simulation, real experiment could be costly.
4. Requires a system that can be driven unstable with increasing proportional gain.

Question 6

state the table of variables in Ziegler-Nichols Tuning

Question 7

measures a process variable and sends the measurement to a controller for
comparison to setpoint. If the process variable is not at setpoint, control action is taken to return the
process variable to setpoint.

Answer 7

feedback loop

Question 8

vary in speed—that is, they can respond to changes in load or to control action
slowly or quickly.

Answer 8

Pressure control loops

Question 9

High-volume systems tend to change more slowly than low-volume systems .

T OR F

Answer 9

T

Question 10

The speed required in a pressure control loop may be dictated by the volume of the
process fluid.

T OR F

Answer 10

T

Question 11

are regarded as fast loops that respond to changes quickly.

Answer 11

flow control loops

Question 12

must have fast sampling and response times.

Answer 12

flow control equipment

Question 13

tend to be rather sensitive devices, they can produce rapid fluctuations or noise in the control signal.

Answer 13

flow transmitters

Question 14

The speed of changes in a level control loop largely depends

Answer 14

on the size and shape of the process vessel
and the flow rate of the input and outflow pipes.

Question 15

Manufacturers may use one of many different
measurement technologies to determine level including ….WHAT?

Answer 15

including radar, ultrasonic, float gauge, and pressure
measurement.

Question 16

are not very quick to respond because it takes time to change the temperature
of a liquid or gas in a process.

Answer 16

Temperature control loops

Question 17

We measure temperature using sensors like

Answer 17

RTDs or thermocouples.

Question 18

To speed things up, we often use a strategy called

Answer 18

“feedforward control.”

Question 19

These sensors send information to
controllers, which can adjust things to keep the temperature on track.

Answer 19

Temperature control loops

Question 20

is a control system that anticipates load disturbances and controls them before they
can impact the process variable.

Answer 20

Feedforward control

Question 21

_________ the user must have a mathematical
understanding of how the manipulated variables will impact the process variable.

Answer 21

For feedforward control to work,

Question 22

are often combined with feedback systems.

Answer 22

feedforward systems

Question 23

Controllers with summing functions are
used in these combined systems to total the input from both the feedforward loop and the feedback loop, and send a unified signal to the final control element

Answer 23

Feedforward Plus Feedback Control

Question 24

is a control system in which a secondary (slave) control loop is set up to control a
variable that is a major source of load disturbance for another primary (master) control loop.

Answer 24

Cascade Control

Question 25

it determines the setpoint of the summing controller in the secondary loop

Answer 25

The controller of the primary loop

Question 26

are those processes that are taken from start to finish in batches.

Answer 26

Batch processes

Question 27

often involve getting the correct proportion of ingredients into the batch.

Answer 27

Batch processes

Question 28

are used at various stages of batch processes.

Answer 28

Level, flow, pressure, temperature, and often mass measurements

Question 29

Imagine a process in which an acid must be diluted with water in the proportion two parts water to one part acid. If a tank has an acid supply on one side of a mixing vessel and a water supply on the other, - a control system could be developed to control the ratio of acid to water, even though the water supply itself may not be controlled.

Answer 29

Ratio Control

Question 30

refers to a control system in which the more important of two variables will be maintained.

Answer 30

Selective control

Question 31

used to allow for an air-rich mixture, but never a fuel-rich mixture.

Answer 31

Selective control

Question 32

is most often used when equipment must be protected or safety maintained, even at the cost of not maintaining an optimal process variable setpoint

Answer 32

Selective control

Question 33

For example, in a boiler control system, if fuel flow outpaces air flow, then uncombusted fuel can build up in the boiler and cause an explosion.

Answer 33

Selective control

Question 34

For example, mixing the ingredients for a juice drinks is often a

Answer 34

batch process.

Question 35

are control loops which a primary controller controls one process variable by sending signals to a controller of a different loop that impacts the process variable of the primary loop

Answer 35

multivariable loops

Question 36

involving just one controlled variable, for instance, temperature

Answer 36

single control loop

Question 37

Examples of Single Control Loops

Answer 37

-Pressure Control Loops -Flow Control Loops -Level Control Loops -Temperature Control Loops

Question 38

process control loops example

Answer 38

-feedback control -single control loops -Multi-Variable / Advance Control Loops

Question 39

Multi-Variable / Advance Control Loops examples

Answer 39

-Feedforward Control -Feedforward Plus Feedback Control -Cascade Control -Batch Control -Ratio Control -Selective Control -Fuzzy Control

Question 40

is a form of adaptive control in which the controller uses fuzzy logic to make decisions about adjusting the process.

Answer 40

Fuzzy Control

Question 41

is a form of computer logic where whether something is or is not included in a set is based on a grading scale in which multiple factors are accounted for and rated by the computer.

Answer 41

Fuzzy logic

Question 42

to create a kind of artificial intelligence that will account for numerous variables, formulate a theory of how to make improvements, adjust the process, and learn from the result.

Answer 42

The essential idea of fuzzy control

Question 43

used to describe autonomous battery powered sensor systems that integrates wireless technology to enables remote sensor values to be reported to a central hub.

Answer 43

WIRELESS INSTRUMENTATION

Question 44

WIRELESS INSTRUMENTATION SYSTEMS TYPICALLY CONSIST OF THREE MAIN COMPONENTS

Answer 44

-Sensors and instruments -Wireless transmitters -Wireless receiver and gateway

Question 45

These devices measure the desired process variables, such as temperature, pressure, flow, or level.

Answer 45

Sensors and instruments

Question 46

These devices convert the sensor signals into digital data and transmit it wirelessly to a receiver.

Answer 46

Wireless transmitters

Question 47

The receiver collects the data from the transmitters and forwards it to a central monitoring system, such as a distributed control system (DCS) or programmable logic controller.

Answer 47

Wireless receiver and gateway

Question 48

ADVANTAGES OF WIRELESS INSTRUMENTATION

Answer 48

-REDUCED INSTALLATION COSTS -INCREASED FLEXIBILITY -IMPROVED SAFETY -ENHANCED ASSET MANAGEMENT

Question 49

Wireless systems are typically less expensive to install than wired systems, as they eliminate the need for wiring and conduit.

Answer 49

REDUCED INSTALLATION COSTS

Question 50

Wireless systems can be installed in areas where wiring is difficult or impossible, such as hazardous environments or moving machinery.

Answer 50

INCREASED FLEXIBILITY

Question 51

Wireless systems reduce the risk of electrical shock and other hazards associated with wired systems.

Answer 51

IMPROVED SAFETY

Question 52

Wireless systems can provide real-time data on the condition of assets, which can help to improve maintenance and planning.

Answer 52

ENHANCED ASSET MANAGEMENT

Question 53

TYPES OF WIRELESS INSTRUMENTATION

Answer 53

-WIRELESS TEMPERATURE SENSORS -WIRELESS FLOW SENSORS -WIRELESS LEVEL SENSORS -WIRELESS VIBRATION SENSORS -WirelessHART -ISA100.11a -Wi-Fi -Cellular -Satellite

Question 54

Applications in Industries of wireless instrumentation

Answer 54

-Oil and Gas -Manufacturing -Healthcare -Agriculture -Transportation

Question 55

Challenges and Considerations of wireless instrumentation

Answer 55

-Signal Interference -Battery Life -Security

Question 56

HOW WILL YOU IMPLEMENT WIRELESS INSTRUMENTATION?

Answer 56

eliminates complex, hardwired installations and makes it easy to deploy and monitor sensor networks across a wide range of application

Question 57

WHAT CAN YOU CONCLUDE REGARDING WIRELESS INSTRUMENTATION?

Answer 57

-it is much easier to deploy in the field relative to their conventional counterparts. -Wired systems can take days or weeks to properly install. scale, troubleshoot and commission. -Wireless instruments require only the sensor to be installed in the process, saving hours or days and valuable resources.