Open loop transfer function

In summary, the open loop transfer function of a control system is typically represented by KG(s)H(s), where G(s) is the forward path gain and H(s) is the feedback gain. Despite the term "feedback" in the equation, there is no actual feedback until the loop is closed. The term H(s) represents the open loop path gain of the difference signal intended for feedback.
  • #1
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In many books i saw that open loop transfer function is given by KG(s)H(s) , where G(s) is forward path gain and H(s) is the feedback gain. But according to the definition of open loop it does not contain feedback , then why there is a term of H(s) ?


reference url
http://en.wikibooks.org/wiki/Control_Systems/Stability
 
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  • #2
G(s).H(s) is the full path gain of the loop you will use for feedback. Or to put it another way, it is the open loop path gain of the difference signal that you intend to connect in as feedback. Until you close the loop there is no feedback, so by definition G(s).H(s) must be some sort of OPEN LOOP gain.

The difference signal, v(in) - v(f), will be amplified by G(s).H(s) and added to v(in). But until we close the loop there is no feedback, so you have a signal vf(s) = G(s).H(s).vin(s)
 
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1. What is an open loop transfer function?

An open loop transfer function is a mathematical model that describes the relationship between the input and output of a system without any feedback. It represents the transfer of signals from the input to the output without any influence from the output.

2. How is an open loop transfer function different from a closed loop transfer function?

The main difference between an open loop transfer function and a closed loop transfer function is that the latter takes into account the feedback from the output to the input. This means that the output of the system can affect the input, resulting in a more complex relationship between the input and output compared to an open loop transfer function.

3. What is the purpose of an open loop transfer function?

The main purpose of an open loop transfer function is to provide a simplified model of a system, which can be used to analyze and design control systems. It allows engineers to understand the behavior of a system and make adjustments to improve its performance.

4. How is an open loop transfer function represented?

An open loop transfer function is typically represented in the form of a transfer function or a block diagram. It can also be represented using mathematical equations or graphs.

5. What factors can affect the accuracy of an open loop transfer function?

The accuracy of an open loop transfer function can be affected by various factors such as external disturbances, nonlinearities in the system, and uncertainties in the parameters. These factors can lead to discrepancies between the actual behavior of the system and the predicted behavior using the open loop transfer function.

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