Home » Sometech » (a) Discuss the basic elements of an automated system. (b) Describe with neat sketch close loop and open loop control system.

(a) Discuss the basic elements of an automated system. (b) Describe with neat sketch close loop and open loop control system.

(a) Basic elements of an automated system:

1. Power to accomplish the process and operate the system.

2. A program of instructions to direct the process.

3. A control system to actuate the instructions.

Elements of Automated system

1. Power source: An automated system is used to operate some process and power is required to drive the process as well as controls. There are many sources of power available, but the most commonly used power is electricity. The actions performed by automated systems are generally of two types:

(a)Processing

(b)Transfer and positioning

In the first case, energy is applied to accomplish some processing operation on some entity. The process may involve shaping, moulding or Loading and unloading. All these actions need power to transfer the entity from one state or condition into more valuable state or condition.

The second type of actions-transfer and positioning. In these cases, the product must generally be moved from one location to another during the series of processing steps.

2. Program of instructions: The actions performed by an automated process are defined by a set of instructions known as process. The programmed instructions determine the set of actions that is to be done automatically by the system. The program specifies what automated system should do and how its various components must function in order to accomplish the desired results.

3. Control system: The control element of the automated system executes the program of instructions.

The controls in an automated system can be:

(a)Closed loop

(b)Open loop.

(b) Closed loop control system: It is also known as a feedback control system. In this system the output variable is compared with an input parameter and any difference between the two is used to drive the output into agreement with input.

1. Input parameter: as set point, represents the desired value of output.

2. Output variables: actual value of parameter.

3. Sensors: A sensor is used to measure the output variable and close the loop

4. Between input and output: It performs feedback function.

5. Controller: The controller compares the output with the input and makes the required adjustment in the process to reduce the difference between them.

6. Actuator: The adjustment being done with one or more actuator which are the hardware devices that physically carry out the control actions such. electric motor, cylinder etc.

Closed loop control system

Open loop control system: It is without the feedback loop. In this case the controls operates without measuring the output variables, so no comparison is made between the actual value of the output and desired input parameters There is always risk that the actuator will not have intended effect on the process.

Open loop control system

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