SEW-Eurodrive DFE24B EtherCAT - Page 71

Manual – Fieldbus Interface DFE24B EtherCAT®
71
8
EtherCAT
®
introduction
Motion Control via EtherCAT
®
activate the required speed change every 5 ms in a single step, but rather in 5 small
steps of 1 ms each.
Position mode
In position mode, a position setpoint is transferred cyclically from the controller to the
inverter and the actual position value is returned by the inverter or a separate encoder.
In Position mode, the inverter follows the constantly changing position setpoint and gen-
erates the required speed setpoint for the speed controller [2] from the position actual
value (from [5] or [6]). The control time-slices of the controller, bus transfer, the internal
processing cycles of the inverter and the encoder must be synchronized.
Once the position in the controller has been referenced to the position in the inverter,
permitted travel ranges or limit switches can be monitored in the inverter. You must
check carefully whether the settings for the load-dependent ramp specification and lag
error monitoring in the inverter are plausible.
To prevent unwanted excessive acceleration during longer control intervals (>1 ms), in-
stead of adopting the position setpoint directly, MOVIDRIVE
®
B uses linear interpola-
tion. This means that for a setpoint cycle of 5 ms, the controller in MOVIDRIVE
®
B does
not activate the required position change every 5 ms in a single step, but rather in 5
small steps of 1 ms each.
6823509003
M
V
X X
X
ref
v
ref
t
ref
X
act
v
act
[C]
[A]
[3]
[2][1]
[4]
[5]
[5] [6]
[B]
x
ref
Position setpoint [1] Position controller [A] Control
x
act
Position actual value [2] Speed controller [B] Fieldbus interface
v
ref
Speed setpoint [3] Output stage of the inverter [C] Inverter
v
act
Actual speed value [4] Driven machine
t
ref
Torque setpoint [5] Encoder (V = speed; X = position)
[6] Optional encoder
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I