A control system is a combination of elements arranged in a planned manner wherein each elements causes an effect to produce an effect a desired output. This cause and effect relationship is governed by a mathematical relation.
If the aforsaid mathematical relation is linear the control system is termed as linear control system. For a linear system the cause (independent variable or input) and the effect (dependent variable or output) are proportionally related and principle of superposition is applicable throughout the operating range of a system.
In a control system the cause acts through a control process which in turn results into an effect.
There may be a variety of systems based on the principle mentioned above but all the systems have many features in common and as such common approach for the study and analysis of control systems is possible.
There may be variety of systems based on the principle mentioned above but all the systems have many features in common and such common approach for the study and analysis of control systems is possible.
Control are systems are in many applications for example, systems for the control of position, velocity, acceleration, pressure, voltage and current etc.
An example of control system
Control of a room temperature is achieved by switching ON and switching OFF of a power supply to the heating appliance. Thus power supply to an appliance is switched ON, when the room temperature is felt low and switched OFF, when the desired temperature is reached.
Open-Loop Control System
Having explained the concept of control action, a control system can described by a block diagram as shown in Figure below;
The input r controls the output c through a control action process. In the block diagram shown in figure above, it is observed that the output has no effect on the control action. Such a system is termed as open-loop control system.
In an open-loop control system the output is neither measured nor fedback for comparison with the input. Faithfulness of an open-loop control system depends on on the accuracy of input calibration.
Closed-Loop Control System
In a closed-loop control system the output has effect on control action through a fedback as shown in figure below and hence closed-loop control systems are also termed as feedback control systems.
The control action is actuated by an error signal e which is the difference between the input signal r and output signal c. This process of comparison between the output and input maintains the output and input maintains the output at a desired level through control action process.
The control systems without involving human intervention for normal operation are called automatic control systems.
A closed-loop (feedback) control system using a power amplifying device prior to controller and the output of such a system being mechanical i.e. position, velocity, acceleration is called servomechanism.
In an open-loop control system the output is neither measured nor fedback for comparison with the input. Faithfulness of an open-loop control system depends on on the accuracy of input calibration.
Closed-Loop Control System
In a closed-loop control system the output has effect on control action through a fedback as shown in figure below and hence closed-loop control systems are also termed as feedback control systems.
The control systems without involving human intervention for normal operation are called automatic control systems.
A closed-loop (feedback) control system using a power amplifying device prior to controller and the output of such a system being mechanical i.e. position, velocity, acceleration is called servomechanism.
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