If the state variables required for a state controllerState variable cannot be measured or are difficult to measure, this can be replaced by monitoring the behaviour of these variables (Figure Z 9). To that end, a mathematical model of the drive in the form of a master loop is developed and recreated with the aid of a permanently running simulation. Equally, this model makes corrections if differences between the real state variables of the subsystem and the simulated state variables of the observer arise due to non-linear influences. The matching achieved in this way is normally completely sufficient in practice.
The state variables required for closed loop position control systems, namely velocity and acceleration, can be taken from the observer.
Alternatively, the velocity and acceleration can also be found by differentiation.
Figure Z 9: Status monitors