The response of servomechanism is the pattern of behavior of the load when a change is made to the input condition, the most important factors being the form which the input change takes and the various restraints, friction, etc. which act on the output.
There are two types of input change to be considered and the names being derived from the shape of the curves of input against time. these are referred to as
- step input and
- ramp input,
A step input is one whereby the input is suddenly changed to a new angular position θi from a null position. Because of the inertia of the load an angular change at the servomechanism output will not be able to follow exactly that at the input, with the result that a large error signal is produced initially. This causes the load to be accelerated to its required position, and thereby reduces the error to zero.
A ramp input is one whereby the input is suddenly moved at a constant speed. In the early stages of the input, and while the error signal is small, the load accelerates slowly and lags behind the input.
