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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.

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