Typical Input Signals
o Impulse Signal
o Step Signal
o Ramp Signal
o Parabolic Signal
Two types of inputs can be applied to a control system. Command Input or Reference Input yr(t).
Disturbance Input w(t) (External disturbances w(t) are typically uncontrolled variations in the load on a control system).
In systems controlling mechanical motions, load disturbances may represent forces.
In voltage regulating systems, variations in electrical load area major source of disturbances.
o One of the types of Modeling a system
o Using first principle, differential equation is obtained
o Laplace Transform is applied to the equation assuming zero initial conditions
o Ratio of LT (output) to LT (input) is expressed as a ratio of polynomial in s in the transfer function.
o The Order of a system is given by the order of the differential equation governing the system
o Alternatively, order can be obtained from the transfer function
o In the transfer function, the maximum power of s in the denominator polynomial gives the order of the system.
o Order of the system is the order of the differential equation that governs the dynamic behaviour
o Working interpretation: Number of the dynamic elements / capacitances or holdup elements between a
o manipulated variable and a controlled variable
o Higher order system responses are usually very difficult to resolve from one another
o The response generally becomes sluggish as the order increases.
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