Basic elements in control systems
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The document presents an overview of control systems, detailing their purpose, types, and key differences between open loop and closed loop systems. Control systems are essential for ensuring the accurate and optimal performance of automatic systems across various applications. Important distinctions include feedback presence and dependency on desired output, highlighting the complexities of closed loop systems compared to open loop systems.
Basic elements in control systems
- 1. Basic elements in control systems Presented by Mr. C.S.Satheesh, M.E., Assistant Professor, Department of EEE, Muthayammal Engineering College (Autonomous), Namakkal (Dt), Rasipuram – 637408 MUTHAYAMMAL ENGINEERING COLLEGE (An Autonomous Institution) (Approved by AICTE, New Delhi, Accredited by NAAC, NBA & Affiliated to Anna University), Rasipuram - 637 408, Namakkal Dist., Tamil Nadu, India.
- 2. Why do we study the control system? To design controllers for a system based on its own properties. It is the basis for ensuring that every automatic system performs its ordained task accurately, efficiently and quickly(optimally)despite being subjected to varying environmental conditions. 2
- 3. Purpose of control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large Industrial control systems which are used for controlling processes or machines. 3
- 4. System 4 When a number of elements or components are connected in a sequence to perform a specific function, the group thus formed is called system
- 5. Control systems 5 A control system is a system, which provides the desired response by controlling the output. The following figure shows the simple block diagram of a control system.
- 6. Contd… Here, the control system is represented by a single block. Since, the output is controlled by varying input, the control system got this name. We will vary this input with some mechanism. In the next section on open loop and closed loop control systems, we will study in detail about the blocks inside the control system and how to vary this input in order to get the desired response. Types of Control Systems: Open Loop Control Systems Closed Loop Control Systems 6
- 7. Open loop control systems 7 The following figure shows the block diagram of the open loop control system. In open loop control systems, output is not fed-back to the input. So, the control action is independent of the desired output. Here, an 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. The traffic lights control system which we discussed earlier is an example of an open loop control system.
- 8. Closed loop control systems 8
- 9. Contd… In closed loop control systems, 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 block (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. So, the controller produces an actuating signal which controls the plant. In this combination, the output of the control system is adjusted automatically till we get the desired response. Hence, the closed loop control systems are also called the automatic control systems. Traffic lights control system having sensor at the input is an example of a closed loop control system. 9
- 10. Difference Between Open loop & Closed loop Control Systems S.No Open Loop Control Systems Closed Loop Control Systems 1. Control action is independent of the desired output. Control action is dependent of the desired output. 2. Feedback path is not present. Feedback path is present. 3. These are also called as non- feedback control systems. These are also called as feedback control systems. 4. Easy to design. Difficult to design. 5. These are economical. These are costlier. 6. Inaccurate. Accurate. 10
- 11. References : A.Nagoorkani, Control Systems, RBA Publications. 11
- 12. Thank You 12