![]() The complete open-loop transfer function( also known as forward transfer function) is no longer in between input \$u(s)\$ and output \$y(s)\$ but set point (reference) value of the output \$r(s)\$ and \$y(s)\$: ![]() Open-loop control procedure does not rely on measurements of the controlled variables and assumes that system behavior is well known and deterministic, therefore it can be controlled without any knowledge what happens with the output value \$y(s)\$. There are two types of control you can apply to the physical system defined as the one above: In the general, the transfer function's behavior, poles and zeros, time constants and characteristic frequencies are different then you want them to be and there for therefore you need a controller. Unstable - at least one pole is positive or equal to zero.DC motor (shaft velocity, armature current).Transfer functions can be stable and unstable: From the transfer function you can ideally find out everything you need to know about the system from the point of view of the control engineer, but that often is not a case. If you have a dynamical system with input \$u(s)\$, output \$y(s)\$ defined as:ĭynamical systems described with transfer functions are idealized, generalized and abstracted, many different systems can be described with the same transfer function. ![]() I just wanted to make things a bit more clear here because it seems that the idea of open loop/closed loop/forward transfer function has got a bit mystified and does not seem exact even though it really is.
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