Technical data

Table Of Contents
Glossary
System Software for S7-300/400 System and Standard Functions - Volume 2/2
Glossary-2
A5E00739858-01
Blending Control
Blending control involves a controller structure in which the setpoint for the total
amount SP is converted to percentages of the individual components. The total of
the blending factors FAC must be 1 (= 100 %).
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Controller 1 Process 1
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Process 4
Controller 4
FAC1
SP1
FAC4
SP4
SP1
LMN1
PV1
LMN4
PV4
Block-Related Message
A message that is configured for a message-capable block (FB or DB).
Cascade Control
Cascade control involves a series of interconnected controllers, in which the
master controller adjusts the setpoint for the secondary (slave) controllers
according to the instantaneous error signal of the main process variable.
A cascade control system can be improved by including additional process
variables. A secondary process variable PV2 is measured at a suitable point and
controlled to the reference setpoint (output of the master controller SP2). The
master controller controls the process variable PV1 to the fixed setpoint SP1 and
sets SP2 so that the target is achieved as quickly as possible without overshoot.
Secondary loop
Main loop
Controller 2
Process 2
Controller 1
PV1
SP1
SP2
PV2
ProcessControl
Process 1
Disturbance variable
Master controller
Slave controller
LMN