Siemens Sinumerik 840DiE sl - Position Controller

01/2007
11.5 Axes and spindles
11-336
© Siemens AG 2007 All Rights Reserved
SINUMERIK 840Di sl Manual (HBIsl) – 01/2007 Edition
11.5.14 Position controller
The closed–loop control of a machine consists of the cascaded closed–loop
control circuits of current controller, speed controller and position controller.
Position
controller
Speed
controller
i
set
n
set
Current
controller
n
act
i
act
Position reference value
from the
Interpolator
Motor
Encoder
Actual position value
SINUMERIK 840Di sl PROFIBUS DP drive
Speed actual value
Actual current value
Fig. 11-16 Control loops
If the axis does not traverse into the desired direction, the appropriate adapta-
tion is made in
S MD32100: AX_MOTION_DIR (traversing direction)
The value ”–1” reverses the direction of motion.
If the control direction of the position measuring system is incorrect, it can be
adjusted with
S MD32110: ENC_FEEDBACK_POL (sign of actual value)
To obtain high contour accuracy, a high loop gain (K
V
factor) of the position
controller is required. However, an excessively high K
V
factor causes overshoot,
instability and impermissibly high machine loads.
The maximum permissible K
V
factor is dependent on the dynamic response of
the drive and the mechanical system of the machine.
If ”0” is entered for the loop gain factor, the position controller will be disconnec-
ted.
Control loops
Traversing
direction
Control direction
Servo gain
11 NCK Commissionin
g
with HMI Advanced