HEIDENHAIN MANUALplus 620 Technical Manual page 808

6.16 The Control Loop
6.16.1 Block diagram of control loop
808
Machine tools normally function on the principle of cascade control. Here the
position control loop is prior to the speed and current control loops.
Benefits of cascade control:
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.
Individual commissioning of each control loop, starting with the innermost
loop.
The position, speed, and current controllers are integrated in the MANUALplus
620. The power module is driven by the CC controller unit through PWM
signals (PWM = pulse width modulation).
There is a separate time interval for each control loop:
Position controller cycle time: Time interval during which the interpolation
points on the path are calculated.
Speed controller cycle time: Time interval in which the actual speed value
is compared to the calculated nominal speed value.
Current controller cycle time: Time interval in which the actual current
value is compared to the calculated nominal current value.
The cycle times that apply vary depending on the CC used or the CC's
settings.
HEIDENHAIN Technical Manual MANUALplus 620