Control System
• Control is a series of actions directed for making a system variable adheres to a reference
value (can be either constant or variable)
• The reference value when performing control is the desired output variable
• Process, as it is used and understood by control engineers, means the component to be
controlled.
• Fundamental structures of control are classified based on the information used along the
control process:
1. Open-loop control (Feedforward)
2. Closed-loop control (Feedback)
Difference:
In open-loop control, the system does not measure the actual output and there is no
correction to make the actual output to be conformed with the reference value.
In feedback control, the system includes a sensor to measure the actual output and uses its
feedback to influence the control process.
Examples: Open-loop or feedback control?
Examples: Open-loop or feedback control?
+/In open-loop control system
+ Generally simpler than closed-loop control
+ Does not require sensor to measure the output
+ Does not, of itself, introduce stability problem
-
Has lower performance to match the desired output
+/In feedback control system
-
More complex than open-loop
Must have steady-state error
Depends on the accuracy of the sensor
May have stability problem
- Process controlled by well-designed feedback control can respond to
foreseen events
- Eliminates the need of human to adjust the control variable
- Gives much better performance with its ability to meet transient response
objectives and steady-state error objectives
Examples: Open-loop or feedback control?
Thank YOU.