Astatic systems are called the systems which have steady-state error which is equal to zero at the established constant input action.

These systems may provide for higher working accuracy.

The characteristic of astatic regulation is parallel to the axis of disturbance signal. But due to regulator inaccuracies it may be located inside of the zone marked by 2 dashed-lines.

To obtain astatic regulation it’s necessary to eliminate rigid connection between the location of control block and the deviation of controlled quantity in order to ensure the system ability to maintain the same X value at any disturbance signal.

This condition may be satisfied if the control algorithm will be as follows:

(2.8)

Or

Indeed, the regulator in this case will be in the equilibrium state only if:

that is at the established value of

Examples:

various electric motors (tacho-generators) whose speed is proportional to control voltage.

We may mention many control laws:

- linear;

- non-linear;

- continuous;

- pulsed;

- digital etc.