User's Manual

PMAC User Manual
168 Writing Programs for PMAC
2a
a
L
L
t = 0
t = 2t
ACCEL
t = t
t = 0
ACCEL
t = t
L
L
t = 0
L
t = t
t = 0
t
t
L
0
MAX.
t
t
A
CCEL
ACCELERATION
VELOCITY
Parabolic
Sinusoidal
S
S
A
CCEL
t = 2t
S
ACCEL
t = 2t
S
TIME
S
S
S
S
S
TIME
t = t - 2t
LACCELS
For Comparison
Parabolic (sinusoidal)
for comparison
a
2
L
A
CCEL S
t = 2t +t
0
4
3
2
1
4
1
3
2
SPECIFY t AND t
ACCEL S
AND ACCELERATION LIMIT
Figure 27 Automatic S Curve Acceleration
Feedrate or Move-Time Specification
The target velocity (feedrate) for the move can be specified, with an F command, or the move time with
the TM command. If F is specified, the move time is calculated, and if TM is specified, the feedrate is
calculated. The relationship between the two values is reciprocal for a given move distance. In either
type of specification, remember that there is an extra TA time at the end of a move or move sequence to
decelerate to a stop. That is, a single move with a specified TM will take TM+TA time from start to stop.
An N-segment move will take
SUM
(I=1 to N)
{TM
I
} + TA
1
/2 + TA
N
/2
to complete. The same is true of feedrate-specified moves, except that TM is calculated as distance
divided by feedrate for each segment, instead of specified directly.