THORLABS KBD101 User Manual page 48

Chapter 6
Current Loop Settings
The motion processor within the TBD driver uses digital current control as a technique to
control the current through each phase winding of the motors. In this way, response times
are improved and motor efficiency is increased. This is achieved by comparing the
required current with the actual current to create a current error, which is then passed
through a digital PI-type filter. The filtered current value is used to develop an output
voltage for each motor coil. The following parameters allow this signal to be tuned for a
fast response and low error when moving to the demanded position.
These parameters are specific to the motor within the stage. Default
values are set at the factory and under normal circumstances do not need
The following two parameters assist in fine tuning the motor drive current
and help reduce audible noise and/or oscillation when the stage is in
motion. A certain amount of trial and error may be experienced in order
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.
48
Note
to be changed.
Note
to obtain the optimum settings.
HA0364T Rev Ck Jan 2017