Emerson FM-3 - Manual (Page 67)

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Setting Up Parameters
This is used to select the acceleration/deceleration type for all motion (homes, jogs and
indexes). The “S-Curve” ramps offer the smoothest motion, but lead to higher peak
acceleration/deceleration rates. “Linear” ramps have the lowest peak acceleration/
deceleration rates but they are the least smooth ramp type. “5/8 S-Curve” ramps and “1/4 S-
Curve” ramps use smoothing at the beginning and end of the ramp but have constant (linear)
acceleration rates in the middle of their profiles. The “5/8 S-Curve” is less smooth than the
“S-Curve” but smoother than the “1/4 S-Curve”.
S-Curve accelerations are very useful on machines where product slip is a problem. They are
also useful when smooth machine operation is critical. Linear ramps are useful in
applications where low peak torque is critical. Below is a comparison of the 4 ramp types:
S-Curve: Peak Acceleration = 2 x Average Acceleration
5/8 S-Curve: Peak Acceleration = 1.4545 x Average
1/4 S-Curve: Peak Acceleration = 1.142857 x Average Acceleration
Linear: Peak Acceleration = Average Acceleration
Ramps Group
Stop Deceleration
The value you enter here defines the deceleration rate which is used when the Stop destination
is activated. The default is 100 RPM/second.
The Stop destination is found in the Ramps Group in the Assignments view.
Feedhold Decel/Accel
When the Feedhold destination is activated, the motor will decelerate to a stop in the time
specified by the FeedholdDecelTime parameter. When feedhold is cleared, the motor will
accelerate back to speed in the same specified period of time.
Feedhold is a means to halt the motor within a velocity profile and then return to the profile
later at the exact same place in the profile. Feedhold does not ramp and does not decelerate
in terms of velocity. Instead, it stops by decelerating time. For example, if the motor is
running at 50 revs/second and feedhold is activated with 2 seconds specified in the
FeedholdDecelTime parameter, then the motor will actually slow and stop in 2 seconds as
measured time (on a time/velocity profile) goes from 100% to 0%.
Travel Limit Decel
The value entered here is the deceleration ramp that is used when a software or hardware
travel limit is hit.