Technical data

Technology objects
CPU 317T: Technology Functions
3-42 A5E00251798-03
Hysteresis
The high limit of the hysteresis is set to 25% of the modulo axis working range, and
to 25% of the non-modulo axis range. The working range is defined by the software
limit switches. The working range is not limited if a SW limit switch does not exist.
You receive an error message if this maximum is exceeded.
• Hysteresis for position-based cams
The hysteresis is enabled immediately after a reversal is detected. Position-
based cams are switched off when they move out of the hysteresis window.
• Hysteresis for time-based cams
The OFF response of a time-based cam is determined by its ON period, not by
the hysteresis.
This is set at the Hysteresis input parameter of the "MC_CamSwitch" technology
function or FB "MC_CamSwitchTime".
3.6.6 Derivative-action times
To compensate for the switching times of digital outputs and connected switching
elements, it is possible to specify derivative-action times. These are derived from
the sum total of all delay times.
Settings for the activation and deactivation times can contain positive or negative
values. A negative activation time must be entered if the cam is to be switched
before its programmed start position.
This is set at the Delay input parameter of the"MC_CamSwitch" or
"MC_CamSwitchTime" technology functions. To maximize switching accuracy:
• Determine the system delay time, based on several measurements at a
constant velocity.
• Set the derived mean value as derivative-action time at input parameter Delay.
The result is a switching accuracy of +/- 70 µs of the high-speed output cams at the
integrated outputs of the Technology CPU. The absolute switching accuracy
(distance or angle) is derived from the set switching accuracy and the current
velocity.
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Derivative-action time = 0; - - - - - - Derivative-action time < 0
Note
The calculation of dynamic adjustments is based on the actual axis velocity at the
time of its internal initiation.
The derivative-action time must allow for DP communication times.
Long derivative-action times (over a modulo cycle) may cause substantial
fluctuation of the switching positions at the actual value cams (actual value profile).
Setpoint output cams should be used in this case.