User manual

264 Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015
Appendix C Program
S-curve Velocity Profile
S-curve velocity profiles are most often used when the stress on the mechanical
system and load needs to be minimized. The acceleration and deceleration time is
balanced against the machine stress using two additional parameters, acceleration
jerk and deceleration jerk.
Depending on the Jerk settings, the acceleration profile can be set to almost pure
rectangular, see Trapezoidal Accel/Decel Time on page 263
(fastest and highest
stress), or to triangular, see Programmable S-curve Accel/Decel Time,
Acceleration Jerk = 60% of Time on page 265 (slowest, lowest stress).
The typical acceleration profile is a trade-off between stress and speed, as shown
in S-curve Accel/Decel Time, Backward Compatibility Setting: Acceleration
Jerk = 100% of Time on page 266.
The Jerk is either specified by the user (either in Units/sec
3
or as a percentage of
maximum) or it is calculated from the percentage of time. (Percentage of time is
equal to the percentage of ramp time in the acceleration/deceleration profile).
Backward Compatibility
The Jerk of 100% of time produces triangular acceleration and deceleration
profiles. These profiles are ones that would have been previously produced as
shown in S-curve Accel/Decel Time, Backward Compatibility Setting:
Acceleration Jerk = 100% of Time on page 266.
j
a
[EU/s
3
] =
a
max
2
[EU/s
2
]
v
max
[EU/s]
200
j
a
[% of time]
()
- 1
j
a
[EU/s
3
] =
d
max
2
[EU/s
2
]
v
max
[EU/s]
200
j
a
[% of time]
()
- 1