Override
The override is used to apply a synchronous online percentage change to the speeds of all the FIFO axes prescribed by the FIFO. There are two logical data channels:
- Instantaneous override changes the override instantaneously to the desired value. This means that it is up to the user to modify the override slowly enough that excessive following errors do not result from the change in override.
- The PT-2 override, which can be parameterised, and which
uses a PT-2 transfer function to modify the override continuously
towards the desired speed according to the difference from the
current speed.
General Notes
The override can be set right at the beginning.
The axes can be stopped through setting override 0.0.
After such a stop, further changes to the override will no longer be accepted.
Instantaneous override
The instantaneous override alters the speed immediately to the
desired value. Since a very sudden change in speed is normally
undesirable, the user is responsible for ensuring that the override
changes appropriately with time (controlled adjustment).
Instantaneous override
PT-2 Override
The PT2 override changes the speed continuously according to the difference between the current speed level and the desired speed level. The progress of this modification is specified by these external and internal parameters
- Discriminate (damping) > 1.0 [ is specified as 1.001]
- Time constant T_0 0.0 < T_0 < ∞ [freely selectable]
- Cutoff, which completes the exponentially gradual decay of an alteration in a finite time [is parameterised internally by means of the reference speeds of the FIFO axes].
PT2-Override
PT-2 Override Time Constant
The time constant T_0 specifies the speed of the level change.
PT2 parameterisation: time constant T_0