Bosch Rexroth IndraDrive MPH-02 Functional Description page 501

MPH-02, MPB-02, MPD-02
Sinusoidal Position Command
Value Profile
Velocity Pulse with Reversal of
Direction
Reference Circle, Reference
Estimation for the Velocity Time
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
Functional Description
For quadrant error correction, static friction possibly occurring at the
reversal points of the direction of motion is compensated by adding an
additional, pulse-shaped command value to the velocity command value
at the output of the position loop. By means of this velocity feedforward
the axis overcomes the static friction faster and with less lag error.
Circular interpolation requires two drives that are controlled by the control
master in cyclic position control. In this case the drives are controlled with
sinusoidal position command value profiles with an angular difference,
related to the circle, of 90 angular degrees between them. The internally
generated velocity command value profiles of the two drives are also
sinusoidal and have an offset of 90°.
When the direction of motion changes, a triangular velocity pulse with a
velocity time range to be set is added to the drive-internal velocity
command value:
velocity pulse
velocity
Fig. 8-64: Schematic curves of velocity pulse and velocity command value with
quadrant error correction
The controller detects changes in the direction of motion by the time flow
of the cyclic position command values.
The settings for quadrant error correction are made when a reference
Radius
circle is processed (radius of reference circle in P-0-0436, Reference
radius for quadrant error correction), e.g. the circle that is demanded
for the reference piece.
The amplitude of the velocity pulse of quadrant error correction is preset
depending on the circular velocity. The pulse is added abruptly and
decreases in a ramp-like way.
The higher the path velocity the higher the pulse and the steeper it
approaches zero, because the velocity time range of the pulse is
independent of the velocity. It corresponds to the value input in P-0-0437,
Velocity time range for quadrant error correction.
For the dimensioning of P-0-0437 it is recommended to estimate the
Range required pulse amplitude and the duration of the pulse. This should be
done with regard to the path velocity and the duration for processing the
reference circle (P-0-0436):
−
P
P-0-0437:
a:
v :
path
b:
T :
circle
Fig. 8-65: Estimation for value of P-0-0437
v(t)
velocity pulse amplitude
velocity time range
1 a
− = ∗
0 0437 *
2 100 %
velocity time range for quadrant error correction
percentage of path velocity
path velocity
percentage of duration for processing of circle contour
duration for processing of circle contour
Drive Functions
time t
DK000054v01_en.fh7
b
∗ ∗
v T
path circle
100 %
8-69