Delta RMC101 - Manual (Page 799)

Appendix C: Parameter Field Reference
C-29
above and solving for the Feed Forward term gives the follow relationship:
Feed Forward <= (10,000 * 1,000) / Target speed
That is, the larger the Speed the smaller the maximum Feed Forward value.
For example, at 30 in/sec Speed, the maximum Feed Forward is:
Max Feed Forward = (10,000 * 1,000)/30,000 = 10,000/30 = 333
If you set Speed to 30,000 and enter a Feed Forward value larger than 333, the value will be
reduced to 333.
Think about this:
If the feed forward value is less than 300, an axis going at a speed of 65535 will not get a full
valve drive from the feed forward term alone. If the feed forward value is less than 200, the axis
drive system is too big and the system may have trouble controlling position. If this happens, then
reduce the gain on the amplifier or use a smaller valve or reduce pressure until the feed forward
terms are over 300.
On hydraulic systems, the extend and retract feed forward terms will be different by the ratio of
the extend and retract surface areas of the position.
The Proportional Gain, Integral Gain and Differential Gain as well as the Integral Drive Limit are
adjusted internally based on the ratio of the Extend and Retract Feed Forwards. The direction
with the lower Feed Forward value will have effectively lower Gains and Integral Limit. This is
done to compensate for the different system dynamics in the two directions.
For example, for a system with an Extend Feed forward of 100 and a Retract Feed Forward of
200 the effective gains in the extend direction will be one half (100 / 200) as big as the specified
gains.
C.2.12 Retract Feed Forward
Default: 100
Range: 0 to 65535
Same as Extend Feed Forward, except that it is used when retracting.
Note: Retracting is the direction that returns decreasing Transducer Counts.
C.2.13 Extend Acceleration Feed Forward
Default: 0
Range: 0 to 65535
The Extend Acceleration Feed Forward causes the controller to give extra drive while
accelerating and a braking drive while decelerating (negative acceleration) in the extend direction.
The drive due to Acceleration Feed Forward is calculated as follows: