NORDAC SK 530E with PosiCon funktion
42
Subject to technical changes
BU 0510 EN
6.5 Taking into account the ratio between master and slave
A ratio between master and slave can be taken into account with the parameters P607 "Ratio" and P608 "Ratio
reduction".
The ratio is entered into the values of the encoder not being used.
In general, in the absolute
encoder (P607 [02] and P608 [02]).
N
Slave
= P607 [xx] / P608 [xx] * N
Master
P105
Slave
= P607 [xx] / P608 [xx] * P105
Master
* 1.05 ... 1.5
P410
Slave
= P104
Master
P411
Slave
= P105
Master
It is also possible to change the ratio relationship between master and slave via an analog input. The ratio
relationship can be varied infinitely between -200% and maximum 200% of the master speed. The analog input can
be scaled according to requirements using the parameters P402/407 and P403/408, see the manual BU 0500.
Negative values cause a rotation direction change. The function of the analog inputs (P400, P405) must be set to
function 47 = ratio factor gearing. It is possible to adjust the ratio relationship "online", however it must be noted
that the "Drag fault" in parameter P630 "Position slip error" can assume significantly greater values during setting
compared to normal synchronised runs, as braking or accelerating must be implemented first to the new speed.
6.6 Achievable accuracies / Position monitoring
The achievable accuracy, i.e. the offset between master and slave drive, depends on several factors. In addition to
the speed control and position control settings, the path, i.e. the drive or the system mechanics also play a decisive
role. The minimum value of the achievable accuracy is however determined by the transmission type. An offset of
0.1 revolutions must be reckoned with at a minimum. In practice, planning should take into account a value greater
than 0.25 motor revolutions. The deviation between master and slave can be monitored by the relay function
"Position reached" in the slave. The relay switches off when the set value in P625 "Relay hysteresis" is exceeded
or if the difference between lead and actual speed exceeds 2Hz + the set value in P104 "Minimum frequency". The
minimum frequency in the slave can be calculated with the following equation:
P104 = 0.25 ... 1.0 * (P625 [rev] * 4.0Hz * P611 [%]) – 2Hz
With a permissible deviation of one revolution and a position control P of 5%, the speed component from the
position control is 20 Hz. If P104 "Minimum frequency" is set to significantly smaller values, the relay message is
determined by the overshooting of the slave speed and not by the maximum position deviation. This applies even
more the shorter the ramp times are set in the slave.
6.7
Significance of P630 for synchronisation
Alternatively, the slip error monitoring P630 "Position slip error“ can be activated in the slave device. When
synchronised control is active, the errors between the positions estimated from the speed and the actual positions
are not compared with each other, instead the difference between the setpoint position and actual position is
calculated as long as synchronisation is active.
Monitoring is only valid when the device is enabled and position control is activated. If the slave is not enabled, the
master position can deviate from the slave position.