Question

Describe the control systems according to the working mode.

Answer 1

A control system is a system, which provides the desired response by controlling the output ie they manages, commands. directs. directs, or regulated the behavior of the system or system.

Here, the control system is represented by a single block. Since the output is controlled by varying input the intermittent box is being termed as control System.

Example - Traffic lights control system, washing machine.

The traffic lights control system is an example of a control system. Here, a sequence of the input signals is applied to this control system and the output is one of the three lights that will be on for some duration of time. During this time, the other two lights will be off. Based on the traffic study at a particular junction, the on and off times of the lights can be determined. Accordingly, the input signal controls the output. So, the traffic lights control system operates on a time basis.

Based on various working modes/conditions control system is categorized into various systems.:-

1. Open Loop and Closed-loop system on the basis of feedback path.

Open-loop control system:-

The output is not fed back to the input, so the control action is independent of the desired output.

Here, the input is applied to a controller and it produces an actuating signal or controlling signal. This signal is given as an input to a plant or process which is to be controlled. So, the plant produces an output, which is controlled.

Closed Loop control system:-

the output is fed back to the input. So, the control action is dependent on the desired output.

The error detector produces an error signal, which is the difference between the input and the feedback signal. This feedback signal is obtained from the feedback elements by considering the output of the overall system as an input to this block. Instead of the direct input, the error signal is applied as an input to a controller, and the error is eliminated.

Although Open-loop control systems are inaccurate they are preferred as they are easy to design and are highly economical.

2. SISO and MIMO Control System on the basis of the number of inputs and outputs present in the system.

If the system consists of single input and single output termed as SISO whereas for multiple inputs and multiple outputs system is termed as MIMO.

3. Continuous and Discrete-time control systems based on the type of signal uses.

If all the signals are continuous in time termed as the continuous-time control systems, whereas in discrete control systems there exist one or more discrete-time signals.