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Control Systems
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CONTROL SYSTEMSPRINCIPLES OF FERMENTATION TECHNOLOGY
CONTROL SYSTEMS“A control system is a device, or set of devices, that manages,
commands, directs or regulates the behavior of other device or system using control loops”
Measuring element
Controller
Final control element
The process to be controlled
Need for Control Systems?
TYPES OF CONTROL SYSTEMS
Control Systems
Automatic
On/Off Control
Proportional Control
Integral Control
Derivative control
Manual
MANUAL CONTROL SYSTEM
Automatic Control System
ON/OFF & PROPORTIONAL CONTROL SYSTEMS
By Mudassir Sultan
ON/OFF CONTROL SYSTEM
• Simplest Feedback Control
• Used for Controlling the Process Variable
• Binary Operation
• Operates between two states
• Maybe Pneumatic or Electronic
Examples: Thermostat
ON/OFF CONTROL SYSTEM
PROPORTIONAL CONTROL SYSTEM
Actuating output is proportional to the Error
c(t) = Kcε(t) + Cs
Kc = Proportional Gain Proportional Gain = 100/Proportional Band
ε(t) = Instantaneous Error ε(t) = SP - PV
Cs = BIAS Signal
Partial Control is possible
PROPORTIONAL CONTROL SYSTEM
PROPORTIONAL CONTROL SYSTEM
INTERGRAL & DERIVATIVE CONTROL SYSTEMS
By Muhammad Salman
COMBINATION OF METHODS OF CONTROL
PI, PD & PID CONTROL SYSTEMSBy Hafiz Muhammad Bilal Fazal
P+I Control System
Proportional action to improve response time and reject disturbance.
Integral action to eliminate steady state error.
Oscillations are reduced.
Finally no offset.
P+D Control System
Proportional plus derivative control is the output response to an error will lead to reduced deviations , faster stabilization and a reduced offset.
Higher the error signal rate of change, the sooner the final control element is positioned to the desired value.
PID Control System
Combination of proportional ,integral and derivative normally provides the best control properties.
Advantages of each system are retained.
Relatively expensive.
MORE COMPLEX CONTROL SYSTEMS By Malik Zeeshan Tariq
COMPLEX CONTROL SYSTEMS
PID control is not adequate to control a disturbance.
Control maybe difficult when there is a long time lag between a change in a manipulated variable and its effect on the measured variable.
Example of a heat exchanger.
CASCADE CONTROL
The output of one controller is the set-point for another.
Each controller has its own measured variable.
In more complex cascade systems more loops maybe included.
CASCADE CONTROL OF A HEAT-EXCHANGE PROCESS
ADAPTIVE CONTROL
If one or more of the process variables or characteristics is not known and cannot be measured.
Useful in circumstances where the process dynamics are not well defined or change with time.
Controlling a batch fermentation where considerable and often complex changes may occur.
ADAPTIVE CONTROL
