WEST POS-124-U-PFN Technical Documentation Manual page 12

Positioning sequence:
The positioning is controlled via Fieldbus. After switching on the ENABLE input, the command position (or
target position) is set equal to the actual position of the sensor and the axis stays in closed loop position con-
trol mode. The READY output indicates that the system is generally ready for operation. After setting the
START-signal, the preset command value will be taken over. The axis immediately will drive to this new com-
mand position and indicates reaching it by setting the InPos output.
The Poswin output stays active as long as the axis is within the preset Poswin window and the START input
is active. The driving velocity is regulated by a signal received by the fieldbus interface. The axis moves with
a limited speed according to this preset value.
The axis can be driven in manual mode (START is off) using the control bits HAND+ or HAND-. The velocity
is programmable. When the HAND signal is deactivated, the command position is set to the actual position
and the system stays in closed loop position control mode.
Setting the synchronous bit (GL) will synchronize both axes and the synchronization controller is overriding
the position controller of axes 2. Axes 2 is now following axes 1 according to the master-slave-principle.
In order to achieve a reliable synchronous control, the maximum speed should be limited to about 70... 80 %
of the possible speed. For compensating for deviations the slave axis must have the ability to move faster
than the master axis. This control margin is necessary and has to be considered during the system design.
Influences on positioning accuracy:
The positioning accuracy is determined by the hydraulic and mechanical conditions. The right choice of valve
is therefore a decisive factor. In addition, two mutually contradictory requirements (short position time and
high accuracy) must be taken into account when designing the system.
The electronic limitations lie mainly in the resolution of the analogue signals, although with our modules a
resolution of < 0.01% only needs to be considered with long positions. In addition, the linearity of the individ-
ual signal points (PLC, sensor and control module) must be considered. The worst-case scenario is that a
system-specific absolute fault occurs.
The repeat accuracy is, however, not affected by this.
Page 12 of 70
volumetric flow
V+
A:A
D:B
V+
P-A
and B-T
MAX:A
control direction
driving out
control direction
driving in
MAX:B
POS-124-U
D:A
A:B
24.01.2022