HEIDENHAIN iTNC 530 Service Manual page 646

Machine tools normally function on the principle of cascade control.
The control loop for
Here the position control loop is prior to the speed and current control loops.
digital axes/
spindles
Benefits of cascade control:
The position, speed and current controllers are located in the iTNC 530.
The power module is driven by the CC 42x (B) through PWM signals.
PWM is the abbreviation for pulse-width modulation. The information content in this signal
depends on the relation of pulse duration to pulse-off duration.
Figure: Simplified illustration of a cascade control for the digital control loop
Figure: Nominal values, actual values and connected devices
1– 646
Transparent structure of the individual control loops.
Disturbances can be compensated through the subsequent controllers.
This relieves the prior controller.
The respective outer control loop protects the inner control loop by limiting the command
variable.
HEIDENHAIN Service Manual iTNC 530