Siemens SIMATIC S7-300 Manual page 250

Description of Functions
Position controller The following error is calculated by periodical comparison of the set position
defined by the interpolator with the actual position of the axis detected by the
encoder. From this error, the position controller calculates the actuating sig-
nal needed for the drive in order to balance to a following error value of zero.
The actuating signal is provided via a D/A converter (DAC) as an analog
signal at the FM 354 output.
Position control loop gain
The positioning loop amplification (K
travel a given following error sets in. The mathematical (proportional) rela-
tionship is:
K
Although the magnitude of the following error plays no dominant role for a
single axis, the K
of the axis:
9-74
Digital setpoint
Digital following error = digital setpoint - digital actual value
Digital DAC value = digital following error DAC factor
Digital
Analog
Voltage setpoint (manipulated value)
Velocity
= =
v
Following error
factor still affects the following important characteristics
v
Positioning accuracy and stopping control
Uniformity of movement
Positioning time
Digital actual value
factor) specifies at what speed of axis
v
3
v [10 MSR/min]
∆s [MSR]
FM 354 Servo Drive Positioning Module