Lenze PLC Designer PLC-Designer (R2-x) SoftMotion - Manual (Page 46)

L-force | PLC Designer - SoftMotion
The SoftMotion drive interface
SM_DriveBasic.lib and automatic code generation
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DMS 5.2 EN 03/2011 TD17
Dead time compensation and filtering for a master/slave connection
The actual positions read-in by an encoder have a certain runtime for control. The setpoints
calculated in the control have a certain runtime as well until they get effective in the drive.
The SMC_Encoder POU offers the possibility to compensate these runtimes by an
extrapolation (advance calculation) of the read-in encoder values. Here, it is required to
filter the position values before extrapolation. A corresponding filter function is also
included in the POU.
In the SMC_Encoder_REF data structure, the dead time compensation and filtering of the
input signal can be activated by writing the elements fDeadTimeCycle and usiFilterDepth.
fDeadTimeCycle: Number of PLC cycles via which the extrapolation takes place.
Depending on the fieldbus, encoder and drive type used, a value between 5.0 and 7.0 cycles
must be entered. The exact value must be detected for the runtime at the machine.
usiFilterDepth: Number of position values via which filtering takes place.
Here, the setting also depends on the quality or accuracy of the read-in actual position and
thus on the encoder used. As starting value, 5 position values are sensible here and an
optimisation is also required. The max. filter depth is 16 position values.

Note!
A too low filter depth causes a disturbed behaviour of the controlled slave axis.
A too high filter depth causes a strong smoothing of the speed variations of the
encoder.