Which of the following statements is not necessarily correct for the open control system?
Right Answer is:
Less accurate than closed loop system
The systems in which output has no effect on the control action are called open-loop control systems. I
Advantages of Open Loop Control System
- Better reliability and stability
- More suitable where accurate positioning of the tools is not required
- Easily buildable
- Less costly
Disadvantages of Closed Loop Control system
- Error cannot be corrected
- Control action depend upon input command
- Presence of non-linearities can cause malfunction.
Why Open Loop control system is Less accurate
Open-loop control systems are those control systems in which the output has no effect on the control action are called open-loop control systems. In other words, in an open-loop control system, the output is neither measured nor fedback for comparison with the input. One practical example is a washing machine. Soaking, washing, and rinsing in the washer operate on a time basis. The machine does not measure the output signal, that is, the cleanliness of the clothes.
In an open-loop control system, the output is not compared with the refer once input. Thus, to each reference input, there corresponds a fixed operating condition, and as a result, the accuracy of the system depends on calibration. In the presence of disturbances, an open-loop control system will not perform the desired task. Open-loop control can be used, in practice, only if the relationship between the input and output is known and if there are neither internal nor external disturbances. Clearly, such systems are not feedback control systems. Note that any control system that operates on a time basis is an open-loop control system. For example, traffic control by means of signals operated on a time basis is another example of open-loop control.