User guide

146 6000 Series Programmer's Guide
S-Curve Profiling (servos only)
S-curve profiling is
not available
during Contouring.
6000 servo controllers allow you to perform S-curve move profiles, in addition to the usual
trapezoidal profiles. S-curve profiling provides smoother motion control by reducing the jerk
(rate of change) in acceleration and deceleration portions of the move profile (see drawing
below).
Decel
Accel
Time
Decel
Velocity
Time
Trapezoidal
Accel
Time
Velocity
Time
S-Curve
Maximum Jerk
Less Jerk
S-curves improve
position tracking.
Because S-curve profiling reduces jerk, it improves position tracking performance in servo
systems, especially in linear interpolation applications (not contouring).
S-curve programming
requirements.
To program an S-curve profile, you must use the average accel/decel commands provided in the
6000 Series programming language. For every maximum accel/decel command (e.g., A, AD,
HOMA, HOMAD, JOGA, JOGAD, etc.) there is an average command for S-curve profiling (see
table below).
Maximum Accel/Decel Commands:
Command Function
Average (S-Curve) Accel/Decel Commands:
Command Function
A Acceleration AA Average Acceleration
AD Deceleration ADA Average Deceleration
HOMA Home Acceleration HOMAA Average Home Acceleration
HOMAD Home Deceleration HOMADA Average Home Deceleration
JOGA Jog Acceleration JOGAA Average Jog Acceleration
JOGAD Jog Deceleration JOGADA Average Jog Deceleration
JOYA Joystick Acceleration JOYAA Average Joystick Acceleration
JOYAD Joystick Deceleration JOYADA Average Joystick Deceleration
LHAD Hard Limit Deceleration LHADA Average Hard Limit Deceleration
LSAD Soft Limit Deceleration LSADA Average Soft Limit Deceleration
PA Path Acceleration PAA Average Path Acceleration
PAD Path Deceleration PADA Average Path Deceleration
The command values for average accel/decel (AA, ADA, etc.) and maximum accel/decel (A, AD,
etc.) determine the characteristics of the S-curve. To smooth the accel/decel ramps, you must
enter average accel/decel command values that satisfy the equation 1/2 A
max
≤ A
avg
< A
max
,
where A
max
represents maximum accel/decel and A
avg
represents average accel/decel. Given
this requirement, the following conditions are possible:
• If A
avg
> 1/2 A
max
, but A
avg
< A
max
, you have achieved an S-curve profile with a
variable period of constant accel/decel (see drawing below).
• If A
avg
= 1/2 A
max
, you have achieved what is called a Pure S-curve profile in which
there is no period of constant accel/decel and jerk is at an absolute minimum (see drawing
below).