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HA0365T Rev D Jan 2017
Chapter 6
Fig. 6.3 Position Setpoint Window
Loop Constants
- When operating in Closed Loop mode, the proportional and integral
(PI) constants can be used to fine tune the behaviour of the feedback loop to changes
in the output voltage or position. While closed loop operation allows more precise
control of the output position, feedback loops need to be adjusted to suit the different
types of piezo actuator that can be connected to the system. The default values of 100
(proportional) and 100 (in tegral) have been optimised to work with most Thorlabs
piezo actuators, so usually these values can be left unchanged.
Proportional
- sets th e proportional feedback loop constant for the selected
channel (0 to 255).
Integral
- sets the integral feedback loop constant for the selected channel
(0 to 255).
Voltage Jog Step Size
- the distance to move when a jog command is initiated. If in
closed loop mode, the step size is measured in microns; if in open loop mode, the step
size is measured in Volts.
Persist Settings to Hardware -
Many of the parameters that can be set for the Piezo
Driver K-Cube can be stored (persisted) within the unit itself, such that when the unit
is next powered up these settings are applied automatically. This is particularly
important when the driver is being used manually in the absence of a PC and USB
link. The
Analogue Input Channel
and
Closed Loop Operation
parameters described
previously are good examples of settings that can be altered and then persisted in the
driver for use in absence of a PC.
To save the settings to hardware, check the ‘Persist Settings to Hardware’ checkbox
before clicking the ‘OK button.
Note
When the KPZ101 and KSG101 are used in closed loop (with the KCHx01)
the pot on the KPZ101 GUI panel (and the OUTPUT control on the top
panel of the unit) controls the position setpoint rather than voltage. This
position setpoint is a percentage (0-100%) reflecting min-max piezo
extension, e.g. for a 30 micron piezo stack, a position setpoint of 50%
equates to 15 micron. Further, when operating in closed loop mode, if you
click on the voltage display of the KPZ101 you are prompted to enter a
'Position Setpoint [0-100%] - see Fig. 6.3 below.
