Detailed description
2.4 Closed-loop control
Basic logic functions: Velocities, Setpoint/Actual Value Systems, Closed-Loop Control (G2)
60 Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Fine Interpolation
The fine interpolator (FIPO) is used to adjust the setpoint of the (generally lower) interpolator
cycle clock to the later position-control cycle.
Fine interpolation further improves the quality of the contour (decreasing the step effect of
the speed setpoint).
There are three types of FIPOs:
1: Differential FIPO
2: Cubic FIPO
3: Cubic FIPO, optimized for operation with feedforward control
The type of fine interpolation can be defined via machine data:
MD33000 $MA_FIPO_TYPE (fine interpolation type).
A differential FIPO not only performs cycle matching but also calculates a mean value
(smoothing) from an IPO cycle.
The cubic FIPO, type 3, supplies the best contour accuracy in addition to the cycle
adaptation.
K
v
factor
To ensure that only low contour deviations occur in continuous-path mode,
a high servo gain factor (K
v
):
MD32200 $MA_POSCTRL_GAIN[n]
is required.
However, if the servo gain factor (K
v
) is too high, instability, overshoot and possibly
impermissibly high loads on the machine will result.
The maximum permissible servo gain factor (K
v
) depends on the following:
• Design and dynamics of the drive
(rise time, acceleration and braking capacity)
• Machine quality
(elasticity, oscillation damping)
• Position-control cycle
The servo gain factor (K
v
) is defined as follows:
9HORFLW\
)ROORZLQJHUURU
>PPLQ@
.9
>PP@
[m/min]/[mm]: Unit of servo gain factor (K
V
) according to VDI standard
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