THORLABS KBD101 User Manual page 49

Brushless DC Servo Driver K-Cube
Current Loop Settings (Settled)
The following parameters are designed to assist in maintaining stable operation and
redusing noise at the demanded position. They allow the system to be tuned such that
errors caused by external vibration and manual handling (e.g. loading of samples) are
minimized, and are applicable only when the stage is settled, i.e. the Axis Settled
status bit (bit 14) is set - see Section 6.3.5.
Note
The following two parameters assist in fine tuning the motor drive current
and help reduce audible noise and/or oscillation when the stage is near
the target position. A certain amount of trial and error may be
experienced in order to obtain the optimum settings.
Dead Error Band – This parameter allows an integral dead band to be set, such that
when the error is within this dead band, the integral action stops, and the move is
completed using the proportional term only. It accept values in the range 0 to 32767.
Feed Forward – This parameter is a feed-forward term that is added to the output of
the PI filter. It accept values in the range 0 to 32767.
Integral Gain – This term provides the 'restoring force' that grows with time, ensuring
that the current error is zero under a constant torque loading. It accepts values in the
range 0 to 32767.
Integral Limit – This term is used to cap the value of the lntegrator to prevent an
excessive build up over time of the 'restoring force', thereby causing runaway of the
integral sum at the output. It accepts values in the range 0 to 32767. If set to 0 then
the integration term in the PI loop is ignored.
Proportional Gain – This term drives the motor current to the demand value, reducing
the current error. It accepts values in the range 0 to 32767.
Digital Output Settings
Caution
The default values programmed into the Kinesis software will give
acceptable performance in most cases. The following parameters are set
according to the stage or actuator type associated with the driver and have
already been optimized. Changing these parameters can result in control
instability and possible damage. Use extreme caution if adjusting these
parameters.
Continuous Current Limit – The system incorporates a current 'foldback' facility, whereby
the continuous current level can be capped. The Current Limit parameter, accepts values
as a percentage of maximum peak current, in the range 0% to 100%, which is the default
maximum level set at the factory (this maximum value cannot be altered).
Excess Energy Limit – When the current output of the drive exceeds the limit set in the
Current Limit parameter, accumulation of the excess current energy begins. The Energy
Limit parameter specifies a limit for this accumulated energy, as a percentage of the factory
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