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Description of Functions
Correction
Drift compensation
Functions
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
Backlash compensation
Mechanical drive components as a rule have a certain amount of backlash
(free play).
Mechanical reversing backlash can be compensated with MD30. In an indi-
rect measuring system (with the encoder on the motor), the mechanical back-
lash is traveled at each change of direction before any axis movement occurs.
The result is positioning errors.
When the position encoder is situated on the machine part to be positioned
(e.g. on a saddle - direct arrangement), backlash adversely affects the achiev-
able K
drive motor (indirect arrangement), a high K
the cost of position deviations that cannot be detected by the position control-
ler. A backlash amount entered in MD30 is applied as a correction by the
position controller as a function of the traveling direction at a given moment,
thus achieving an approximate compensation for backlash in positioning.
MD31 is used to label the "backlash-free" or "accurate-measurand" traveling
direction of the axis. If MD31 = 0, the "backlash-free" direction is the one
that matches the direction of axis movement when synchronization is re-
corded. Depending on MD18, this will correspond to the following associa-
tion:
MD18 = 0, 2, 4, 8: Plus direction is backlash-free
MD18 = 1, 3, 5, 9: Minus direction is backlash-free
30
31
9-80
MD
Designation
Control signals
–
Backlash
factor. On the other hand, if the position encoder is attached to the
v
MD
Designation
Backlash compen- sation –1 000 000 – +1 000 000
Directional reference of
backlash
Value/Meaning
16 = automatic drift compensation
active
+
Spindle
factor can be achieved, but at
v
Value/Meaning
0 = as in reference point approach
(only for incremental encoders)
FM 453 Servo Drive / Step Drive Positioning Module
C79000-G7076-C453-01
Unit
–
Unit
(MSR)
–
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