Rockwell Automation 1398-PDM-xxx IQ Master Version 3.2.4 for IA-2000 and IQ-5000 Positioning Drive Modules, IQ-55 - Manual (Page 180)

158 Motion • Gearing
Publication 1398-PM601A-EN-P — October 2000
TUTORIAL
D = 1, V = 20 ;Accel to 20 in a distance of 1
DIF = 4, I1 = ON, JUMP STOPNOW ;If input 1 comes on stop now else
STOPNOW: ;Stop after a distance of 4
D = 1, V = 0 ;Decel to a stop in a distance of 1
S-Curve Acceleration
Instead of using linear acceleration, motion created using stick moves (DV commands) can use S-Curve
acceleration. The syntax for a DV move with S-Curve acceleration is:
D = distance, V = velocity, S
Sticks using S-Curve acceleration will take the same amount of time as linear acceleration sticks.
S-Curve acceleration is useful because it is much smoother at the beginning and end of the stick, how-
ever, the peak acceleration of the stick will be twice as high as the acceleration used in the linear accel-
eration stick.
Gearing
For some applications, it may be desirable to tie the motion of one axis to another for simultaneous
movement at some fixed ratio or gear. The GEAR instruction allows this kind of “electronic gearing.”
You can use the GEAR instruction to tie the motor to the motion of encoder 2, so that when encoder 2
moves a given distance, the motor moves a proportional distance. The proportion is set by the GEAR
instruction.
The GEAR is established in units of encoder counts and is set as the number of encoder counts to com-
mand the motor for each encoder count received from encoder 2. A gear of 2/3 would result in 2/3 of a
count being commanded for each count on encoder 2.
Negative gear ratios are also allowed. A negative gear will cause the motor to move in the direction
opposite to that of encoder 2.
Once the gear ratio is set with the GEAR instruction, electronic gearing must be enabled before the
motor will begin following. GEAREN = ON is used to enable the gear and GEAREN = OFF is used to
disable the gear.
In some cases, the encoder may be able to accelerate faster than the motor or load. In this case, a maxi-
mum acceleration limit for the motor can be set that is acceptable both to the motor and load. The
SLEW instruction sets the slew rate and SLEWEN = ON enables this limit.
The slew limit is particularly useful when encoder 2 is in motion before the gear is enabled. If there was
Velocity
20
Input 1 ON
Normal end
of Move Conditional end
of Move
Time