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28 A. TUNÇER, G.T. TAYYAR and Y. ÜNSAN

Figure 5.2 Open-loop system [17]

Figure 5.3 Closed-loop system [17]

Elements of a simple closed-loop can be sorted as follows;

 Comparison Element:
This element calculates an error value from the required value of the controlled variable
and the achieved value provided from the feedback signal.

 Control Element:
Control element determines whether to increase or decrease the value of the input
according to the calculated error value. Basically determines the course of action
according to the error.

 Correction Element:
Correction Element is the actuating component which produces the change designated by
the control element, e.g. an actuator, a motor or an air condition unit.

 Process:
Process is the system containing the variable that is being controlled. E.g. driven length of
an actuator, rpm of a motor or temperature inside a vessel.

 Measurement Element:
Measurement element is the measurement signal from the controlled variable in the
process.

Figure 5.4 Closed loop elements [17]

GiDB|DERGi Sayı 7, 2016