Document Number: P-SS-004-09 Rev 5
Old Numbers (AS6007H, A-SS-004-20208)
Revised 11/20/2003
www.DanaherMotion.com
Page
14
This example assumes that the input encoder resolution (ENCIN) accurately represents the input
encoder resolution. If not, the formula must be modified:
VELOCITY
SLAVE
= VELOCITY
MASTER
*
(GEARI/GEARO)
* (
Encoder resolution/ENCIN)
For example, suppose you have a 500-line encoder which you want to electronically gear at 1:1.
You would select ENCIN as 512, the closest allowable setting to 500 and adjust the gear ratio to
correct for the difference between 500 and 512. For example, you could set GEARI = 8192 and
GEARO = 8000, as in Figure 15. The programming window shows the input pulses per revolution
as the desired 500 (just above the
OK
button).
The SERVO
STAR
S600 does not accumulate round-off error, even when the gear ratio is non-
integer. It uses exact integer math, keeping track of the remainder. This eliminates round-off error
from accumulating, even after many revolutions.
The use of a large electronic gear ratio usually produces noisy operation because a single pulse from
the master produces a burst equivalent to multiple pulses on the electronically-geared drive. The
higher the servo gains of the geared drive, the more the system demonstrates this problem. Avoid
gear ratios much greater than one, especially on highly responsive systems. If you are using a
multi-pulse generator (MPG), be sure the resolution of the generator is fine enough that the gear
ratio is not much more than one.
Realtime Adjustments
You can adjust the gear ratio of the SERVO
STAR
S600 in realtime. Use caution when changing
the gear ratio on-the-fly as this could produce unexpected results.
Realtime gear ratio variation is accomplished by modifying the constants GEARI or GEARO while
the machine is in operation. The commands to change these constants are communicated via the
serial port or via a field bus connection, such as CANopen or PROFIBUS. You cannot use gearing
via SERCOS interface
TM
.
You can adjust the gear ratio using the analog input to modify the gear ratio. In this case,
GEARI/GEARO defines the nominal gear ratio and the analog input acts as a modifier to provide
the effective gear ratio. The analog input can raise or lower the gear ratio
