21
Rev. 1.0
0006302011
SSM24C User Manual
+86-400-820-9661
4.2 Basic Configuration
The default control modes for the SSM24C integrated step servo is SCL mode.
There are total 5 sets of parameters, 4 of them need to be configured.
4.2.1 Maximum Currents
Continuous - The current that can be sustained indefinitely.
Boost - An SSM drive can provide a momentary current boost. This
allows for greater acceleration rates than would otherwise be possible.
To assure reliable motor operation, the drive automatically ramps the
current down after one second so that the average current does not
exceed the motor’s rating.
4.2.2 Encoder
Encoder res
olution is fixed at 20000 counts/rev.
4.2.3 Electronic Gearing
Genarally, we recommend using the default setting 20000 steps/rev.
With Electronic Gearing drive response to incoming step pulses can be
adjusted. This is very useful when a step motor drive is being replaced with a step-servo system,
as the SSM can have the same number of steps/revolution as the stepper. For example, SSM24C
can be programmed to operate at 200 steps/rev, like a full step drive. If the system is working in
degrees, the drive can be programmed to operate at 36,000 steps/rev resulting in an even number
of steps (100) per degree.
4.2.4 Positioning Error Fault
Positioning error is the difference, in encoder counts, between
the actual position and the commanded position of the motor.
A small amount of positioning error is a normal part of a step-
servo system. In the event of a broken wire, a failed sensor, the
motor encounting a physical obstruction, or operator error, a
position error fault limit can prevent damage to the system. Anytime the position error (as reported
by the encoder) exceeds this set limit, the drive is disabled and a fault alarm occurs.
The fault limit can be set as low as 10 encoder counts, or as high as 32000. During initial tuning
of the system, this value should be set high so that the drive doesn’t shut down while the tuning
parameters are being adjusted. Once the drive is properly tuned and the expected amount of
error during normal operation is known, an appropriate fault limit can be set. For example, with
QuickTuner’s oscilloscope function set to plot position error, sample moves using the maximum
speed and acceleration planned for use in an application should be executed. If the maximum
position error is 50 counts, the fault limit could safely be set at 100.
4.2.5 Maximum Acceleration
This sets the maximum level of acceleration for the motor. Even if the command input tries to
demand a higher level of acceleration, the drive will only accelerate at the set maximum level.
