The objective of the control system is to control the variable (c) in a prescribed manner by the actuating signal (e) through the elements of the control system.
Type of control system
- Open-Loop Systems (Non-Feedback System)
The open-loop system is capable of adapting to a variety of operating conditions and is able to respond to a class of input satisfactorily. In this feedback isn’t present. There is no error detection and is generally stable.
But the operation is affected by the non-linearities. This type is more prone to inaccuracies since accuracy depends on the calibration of input. The open-loop is easier o construct and has less maintenance.
- Closed-Loop Systems (Feedback System)
In closed-loop systems, in order to obtain more accurate control, the controlled signal is fed back and compared with the reference input. Then, an actuating signal proportional to the difference of the output and the input is sent through the system to correct the error. In this type, feedback is present and therefore, errors are detected.
It is unstable. Accuracy of the system is dependent on feedback therefore, it’s more accurate. This type of is adjusting in nature and doesn’t get affected by the non-linearities. This system is complicated and requires more maintenance.
Types of Feedback Control System
- Linear vs. Non-linear System
The classification is based on the methods of analysis and design. These methods has the magnitudes of the signals which are limited to a range in which system components exhibit linear characteristics (linear).
But, when the magnitudes of the signals are extended outside the range of the linear operation it’s no longer linear, thus,to improve performance or more effective control non-linearities are introduced.
- Time-Invariant vs. Time-Variant System
When the parameters of a control system are stationary with respect to time during the operation, we have a time-variant system if it drifts or varies with time to some extent.
- Continuous Data
A continuous data system is one in which signals are various part of the system are all function of the continuous-time variable (t).
- Sampled Data & Digital
These are different from the continuous data systems in that the signals at one or more points of the system are in the form of either a pulse train or a digital code.