Feed-Forward Control Function - YASKAWA SGM Series User Manual

Determining the Electronic Gear Ratio (B/A)
B = [(Cn-0011) × 4] × (motor shaft revolution speed)
A = [Load travel distance per load shaft revolution (reference units)] × (load shaft speed)
Reduce the electronic gear ratio (B/A) to the lowest terms so that both A and B are less than
32768, and then set A and B in Cn-0025 and Cn-0024.
J Motor Shaft and Load Shaft Revolution Speed
The motor shaft and load shaft speeds form the gear ratio for the mechanical system. If the me-
chanical system is structured so that load shaft makes "l" revolutions when the motor shaft makes
"m" revolutions, the gear ratio for the motor shaft and the load shaft is m/l, as shown below.
Fig. 5.2 shows a block diagram of the electronic gear function.
Differ-
entiation
Cn-001F
to 0021
MECHATROLINK
POSING Command
Accel/
decel

5.2.2 Feed-forward Control Function

The feed-forward control function performs differentiation of position and add it to speed refer-
ence in order to shorten positioning time. Set the amount of feed-forward control (0% to 100%)
in Cn-001D, but do not set the level too high, because this may cause overshooting with small
loads.
A primary lag filter can be added for the feed-forward reference. If it is added, set the time
constant for the primary lag filter in user constant Cn-0027.
Load travel distance per load shaft revolution = 12/0.01 = 1200 (reference units)
Motor shaft speed: m (revolutions)
Load shaft speed: l (revolutions)
Cn-0024
Cn-001D
Cn-0025
Feed-forward
gain
Cn-0024
Error
counter
Cn-0025
Figure 5.2 Block Diagram of the Electronic Gear Function
5 -5
Cn-001C
Cn-0023
Bias
Primary
lag filter
Cn-0004
Cn-001A
Cn-0005
Speed loop
5.2 Position Control
Cn-001B
PSET
SGMj
Servomotor
Current loop
5