FEEDBACK

FEEDBACK

FEEDBACK

The mechanism of feedback has a very simple definition: “the returns to the input of a part of the output”. The control of a system requires getting information from the output back to the input of a system and this is called feedback. Thus, feedback is the function that provides the information on the deviation of output from standard and delivers this information as input into this process from which the output was derived. Feedback element is the arrangement for collecting information on the comparison of output to control standard and for delivering this information as input to the system so that deviation from expected output can be corrected through the management process.

A feedback loop is to be added to this basic system to achieved control. Then output of the system is compared with the desired output, better we call it, standard. If any deviation is found between the two, signals are passed to the input and consequently adjustments are made in the processing activities to get the desired output.

KINDS OF FEEDBACK

1. OPEN LOOPS

This system is set up to achieve one purpose and there is no feed back of information. In this system, with inputs, process and outputs that have no connection or information flow from the output back to the input. Here control depends on inputs and process being correct. Nobody collects data regarding output and compare it with the standard.

2. CLOSED LOOPS

In a closed loop control system information about the process or output is fed back to a controller who adjusts the input and system as necessary.

CLASSIFICATION OF THE FEEDBACK CONTROL SYSTEM

1. POSITIVE FEEDBACK CONTROL

In every feedback loop, as the name suggests, information about the result of transformation or an action is sent back to the input of the system in the form of input data. If these new data facilitate and accelerate the transformation in the same direction as the preceding results, they are positive feedback-their effects are cumulative. If we call a feedback mechanism positive if the resulting action goes in the same direction as the condition that activates it.

Positive feedback reinforces the direction in which the system is moving. In other words in a positive feedback system an action or adjustment is repeating to until the desired output is achieved. For example a programmer can apply the concept of modular programming structure in developing a program. The modular approach is first applied on small projects. If the result is found to be encouraging i.e. positive feedback, he again tries to apply the concept still on a larger project. This process continues until he finishes his project yielding the desired results.

In the feedback control system, changes or adjustments are made not in the output only. If the standard is not achievable in spite of putting all efforts, the organization may change its standards or goals. Organizations are operating to achieve certain goals. If the goals are not achievable, the organization has to change the system itself to attain new goals.

2. NEGATIVE FEEDBACK CONTROL

A system whose performance is deviating from the attainments of its goal generates negative feedback. The one generally used in cybernetics is negative feedback, and these acts oppose the input. For example, the external temperature rises the system will activate a cooling system to maintain the refrigerator temperature as required output.

It allows the system to operate with in certain limits of performance. A system is said to be out of control if it functions outside the allowable limit. In this case there will be a failure of control mechanisms. The aim of negative feedback control system is to convert a system into a self regulating and self monitoring system.

Negative feedback control can be achieved by:-

1. Detecting feedback with sensor
2. Measure the size, quantity or intensity of feedback.
3. Comparing the results to the established standards of performance.
4. Transmitting control signals that initiate corrective action to adjust the activities of other system components.
5. Bringing the system performance under control.

The following four elements are included in a negative feedback control system:-

1. A characteristic or condition to be controlled. It should be a measurable standard.
2. A sensor for measuring this condition or output.
3. A consol unit to compare the output with the standard.
4. An activating unit which generates a corrective input signal to the process.