Siemens SIMATIC S7-300 Manual page 251

The following relationship applies for these characteristics:
The better the axis design, the greater the achievable K
the axis parameters from the technological viewpoint. The size of the K
tor is especially affected by the time constants, backlash and spring compo-
nents in the controlled system. In real applications the K
within the following bandwidth:
The MD38 value is input with a resolution of 10
value results:
MD38 = 10
38
Drift compensation
Thermal conditions will shift the zero error in the control loop during opera-
tion. This effect is called drift. In a closed control loop with a proportional-
action controller, this results in a temperature-dependent positioning error.
You can activate automatic drift compensation with MD37, under which con-
tinuous balancing takes place in the positioning control loop.
A basic compensation of the zero point error by means of the offet is required
for the optimum effect of the drift compensation
(see MD44, offset compensation).
37
FM 354 Servo Drive Positioning Module
K = 0.2...0.5 poor-quality axis
v
K = 0.5...1.5 good axis (normal case)
v
K = 1.5...2.5 high-quality axis
v
3 3
K = 10
v
Following error
MD Designation
Positioning loop amplifi-
cation
MD Designation
Servo control signal
Description of Functions
factor, and the better
v
factor moves
v
3
, so that the following input
v [10
Velocity
3
= 10
Value/Meaning
0...10,000
Value/Meaning
16 = automatic drift compensation
active
fac-
v
3
MSR/min]
∆s [MSR]
Unit
[(MSR/min)/MSR]
Unit
–
9-75