process control loops and wireless instrumentation Flashcards
Start with closed-loop system with a proportional controller.
Ziegler-Nichols Tuning Method
4 steps of Ziegler-Nichols Tuning Method
- Begin with a low value of gain, Kp
- Reduce the integrator and derivative gains to 0
- 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.
- Note that the value Kcr and the corresponding period of sustained oscillation, Pcr sustained oscillation with period Pcr. (Pcr is measured in sec.)
state the table of Ziegler-Nichols Tuning Method
Advantages of Ziegler-Nichols Tuning
- It does not require expert knowledge.
- It does not require model / simulation of system.
- Often produces good initial Kp,Ki,Kd.
Disadvantages of Ziegler-Nichols Tuning
- It is not mathematically rigorous.
- Requires a stable system.
- If you do not have a model / simulation, real experiment could be costly.
- Requires a system that can be driven unstable with increasing proportional gain.
state the table of variables in Ziegler-Nichols Tuning
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.
feedback loop
vary in speed—that is, they can respond to changes in load or to control action
slowly or quickly.
Pressure control loops
High-volume systems tend to change more slowly than low-volume systems .
T OR F
T
The speed required in a pressure control loop may be dictated by the volume of the
process fluid.
T OR F
T
are regarded as fast loops that respond to changes quickly.
flow control loops
must have fast sampling and response times.
flow control equipment
tend to be rather sensitive devices, they can produce rapid fluctuations or noise in the control signal.
flow transmitters
The speed of changes in a level control loop largely depends
on the size and shape of the process vessel
and the flow rate of the input and outflow pipes.
Manufacturers may use one of many different
measurement technologies to determine level including ….WHAT?
including radar, ultrasonic, float gauge, and pressure
measurement.
are not very quick to respond because it takes time to change the temperature
of a liquid or gas in a process.
Temperature control loops
We measure temperature using sensors like
RTDs or thermocouples.
To speed things up, we often use a strategy called
“feedforward control.”
These sensors send information to
controllers, which can adjust things to keep the temperature on track.
Temperature control loops
is a control system that anticipates load disturbances and controls them before they
can impact the process variable.
Feedforward control
_________ the user must have a mathematical
understanding of how the manipulated variables will impact the process variable.
For feedforward control to work,
are often combined with feedback systems.
feedforward systems
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
Feedforward Plus Feedback Control
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.
Cascade Control
it determines the setpoint of the summing controller in the secondary loop
The controller of the primary loop
are those processes that are taken from start to finish in batches.
Batch processes
often involve getting the correct proportion of ingredients into the batch.
Batch processes
are used at various stages of batch processes.
Level, flow, pressure,
temperature, and often mass measurements
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.
Ratio Control
refers to a control system in which the more important of two variables will be
maintained.
Selective control
used to allow for an air-rich mixture,
but never a fuel-rich mixture.
Selective control
is most often used when equipment must be protected or safety maintained, even at the cost of not maintaining an optimal process variable setpoint
Selective control
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.
Selective control
For example, mixing
the ingredients for a juice drinks is often a
batch process.
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
multivariable loops
involving just one controlled variable, for instance, temperature
single control loop
Examples of Single Control
Loops
-Pressure Control Loops
-Flow Control Loops
-Level Control Loops
-Temperature Control Loops
process control loops example
-feedback control
-single control loops
-Multi-Variable / Advance
Control Loops
Multi-Variable / Advance
Control Loops examples
-Feedforward Control
-Feedforward Plus Feedback Control
-Cascade Control
-Batch Control
-Ratio Control
-Selective Control
-Fuzzy Control
is a form of adaptive control in which the controller uses fuzzy logic to make decisions
about adjusting the process.
Fuzzy Control
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.
Fuzzy logic
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.
The essential idea of fuzzy control
used to describe autonomous battery powered sensor systems that integrates wireless technology to enables remote sensor values to be reported to a central hub.
WIRELESS INSTRUMENTATION
WIRELESS INSTRUMENTATION SYSTEMS TYPICALLY CONSIST OF
THREE MAIN COMPONENTS
-Sensors and instruments
-Wireless transmitters
-Wireless receiver and gateway
These devices measure the desired process variables, such as
temperature, pressure, flow, or level.
Sensors and instruments
These devices convert the sensor signals into digital data and transmit it wirelessly to a receiver.
Wireless transmitters
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.
Wireless receiver and gateway
ADVANTAGES OF WIRELESS
INSTRUMENTATION
-REDUCED INSTALLATION COSTS
-INCREASED FLEXIBILITY
-IMPROVED SAFETY
-ENHANCED ASSET MANAGEMENT
Wireless systems are typically less expensive to install than wired systems, as they eliminate the need for wiring and conduit.
REDUCED INSTALLATION COSTS
Wireless systems can be installed in areas where wiring is difficult or
impossible, such as hazardous environments or moving machinery.
INCREASED FLEXIBILITY
Wireless systems reduce the risk of electrical shock and other hazards associated with wired systems.
IMPROVED SAFETY
Wireless systems can provide real-time data on the condition of
assets, which can help to improve maintenance and planning.
ENHANCED ASSET MANAGEMENT
TYPES OF WIRELESS INSTRUMENTATION
-WIRELESS TEMPERATURE SENSORS
-WIRELESS FLOW SENSORS
-WIRELESS LEVEL SENSORS
-WIRELESS VIBRATION SENSORS
-WirelessHART
-ISA100.11a
-Wi-Fi
-Cellular
-Satellite
Applications in Industries of wireless instrumentation
-Oil and Gas
-Manufacturing
-Healthcare
-Agriculture
-Transportation
Challenges and Considerations of wireless instrumentation
-Signal Interference
-Battery Life
-Security
HOW WILL YOU IMPLEMENT WIRELESS
INSTRUMENTATION?
eliminates complex, hardwired
installations and makes it easy to deploy and monitor
sensor networks across a wide range of application
WHAT CAN YOU CONCLUDE REGARDING
WIRELESS INSTRUMENTATION?
-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.
