Feed Forward Function - Panasonic MINAS A6 Series Operating Instructions Manual

5. Manual Gain Tuning (Application)

Feed forward function

Usage example of velocity feed forward
The velocity feed forward will become effective as the velocity feed forward gain is
gradually increased with the velocity feed forward filter set at approx. 50 (0.5 ms). The
positional deviation during operation at a constant velocity is reduced as shown in the
equation below in proportion to the value of velocity feed forward gain.
Positional deviation [unit of command] = command speed [unit of command/s] /
Command speed
With the gain set at 100 %, calculatory positional deviation is 0, but significant overshoot
occurs during acceleration/deceleration.
If the updating cycle of the positional command input is longer than the driver control
cycle, or the pulse frequency varies, the operating noise may increase while the velocity
feed forward is active. If this is the case, use positional command filter (1st delay or FIR
smoothing), or increase the velocity forward filter setup value.
Usage example of torque feed forward
• To use the torque feed forward, correctly set the inertia ratio.
Use the value that was determined at the start of the real time auto tuning, or set the
inertia ratio that can be calculated from the machine specification to Pr0.04 Inertia ratio.
• The torque feed forward will become effective as the torque feed forward gain is
gradually increased with the torque feed forward filter is set at approx. 50 (0.5 ms).
• Positional deviation at a constant acceleration/deceleration can be minimized close
to 0 by increasing the torque forward gain. This means that positional deviation can
be maintained at near 0 over entire operation range while driving in trapezoidal speed
pattern under ideal condition where disturbance torque is not active .
Positional deviation
Command speed
Zero positional deviation is impossible in actual situation because of disturbance torque.
As with the velocity feed forward, large torque feed forward filter time constant decreases
the operating noise but increases positional deviation at acceleration change point.
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positional loop gain [1/s] × (100 - velocity feed forward gain [%]) / 100
Pos t ona dev at on
Motor speed
Motor speed
Velocity feed forward gain = Fixed 100[%]
Torque feed forward
0[%]
50[%]
100[%]
Ve oc ty feed forward ga n
0[%]
50[%]
80[%]
Time
gain
Time
Positional deviation within the
constant speed range will
reduce as the velocity
forward gain is increased.
Positional deviation in the
region where acceleration
is constant can be reduced
by torque feed forward.