User`s manual

7-48 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
7
Triangular Velocity Profiles
The triangular velocity profile minimizes servo acceleration rate and requires a higher servomotor
velocity when compared to a trapezoidal profile of the same distance and time. Use a triangular
profile for fast short moves.
t
t
a
a
t
t
d
d
Vpk
Vpk
time
time
Td
Td
A
A
D
D
X
X
Ta
Ta
Position = Area
Position = Area
Velocity
Torque
Figure 7-24. Triangular Velocity Profile
Non-Linear or S-Curve Acceleration
S-Curve or jerk limited acceleration calculation is simple to do if the linear calculation is
accomplished first. The APM and DSM motion controllers use 100% jerk limiting. To convert a
linear acceleration to 100% jerk limited acceleration you either double the Acceleration value
(2*A) or double the time used for acceleration (2t
a
). Using S-Curve acceleration at the same
acceleration rate (A) as linear acceleration will require twice the time (t
a
) reaching velocity. If the
time duration of the move must remain the same and the servo has sufficient peak torque, use
twice the acceleration (2*A) to reach velocity in the same amount of time.
Equations:
X
a
= X
d
=
a
V
2
pk
t
a
= t
d
=
a
2V
pk
t
s
=
pk
s
V
X
Figure 7-25. S-Curve Acceleration
Vpk
t
a
t
Velocity
Acceleration
ta
Xa
Xs
Xd
td
ts
a
pk
da
pk
dapk
t
V
a
tt
x
V
ttVx
=
+
=
+=
)(
)(2
)(
2
1
Equations: