2.3.3.3.88. NXspm_positioner¶
Status:
base class (contribution), extends NXpositioner
Description:
An extension of positioner, used to maintain a measurement signal through ...
An extension of positioner, used to maintain a measurement signal through a feedback loop, specialized for scanning probe microscopy applications.
The component positions the spm head or cantilever tip on the surface of the sample thus maps 2D scan of the sample.
Symbols:
No symbol table
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Structure:
z_controller: (optional) NXpid_controller
This controller's task is to continuously adjust the Z position of tip (e.g., ...
This controller’s task is to continuously adjust the Z position of tip (e.g., in topography scan in STM/STS experiment) in order to keep the selected control signal as close as possible to the Set Point. Different control signals lead to different controller’s behavior.
The second PID feedback loop intends to position the tip in the Z direction.
p_gain (proportional gain) from z_controller refers to K_p value from PID controller. i_gain (integral gain) from z_controller refers to K_i value from PID controller. setpoint from z_controller refers to setpoint from PID controller.
Usually, the same controller, (z_controller) will be used for positioning the tip in three dimensional space. In this case, the controller coefficients (proportional, integral, differential) and other characteristic constants will be the same. Otherwise, for separate controllers positioning the tip in 3D space use the feedback controller in actuator.
D_t: (optional) NX_NUMBER {units=NX_TIME}
The derivative time constant of the derivative part of the PID controller. P ...
The derivative time constant of the derivative part of the PID controller. Proportional Derivative constant K_d can be expressed as \(K_d = K_p D_t\).
I_t: (optional) NX_NUMBER {units=NX_TIME}
The integral time constant of the integral part of the PID controller. Propo ...
The integral time constant of the integral part of the PID controller. Proportional Integral constant K_i can be expressed as \(K_i = \frac{K_p}{I_t}\).
z: (optional) NX_NUMBER {units=NX_LENGTH}
To indicate the relative tip position z between tip and sample. The tip posi ...
To indicate the relative tip position z between tip and sample. The tip position can also be varied when the z_controller is not running.
set_point: (optional) NX_NUMBER {units=NX_ANY}
The set point for the z-controller to be fixed and the target value could be ...
The set point for the z-controller to be fixed and the target value could be height or current.
feedback_on: (recommended) NX_BOOLEAN
The status of the controller PID feedback system in z-axis is ON / OFF. ...
The status of the controller PID feedback system in z-axis is ON / OFF. E.g., for constant height mode, the z-controller feedback system is off.
tip_lift: (optional) NX_NUMBER {units=NX_LENGTH}
If the tip is lifted from the stable point.
switch_off_delay: (optional) NX_CHAR_OR_NUMBER {units=NX_TIME}
The switch-off delay of the controller from its stable point.
z_offset_value: (optional) NX_NUMBER {units=NX_LENGTH}
Offset added to the initial averaged tip position on Z-axis before starting ...
Offset added to the initial averaged tip position on Z-axis before starting scan.
z_average_time: (optional) NX_NUMBER {units=NX_TIME}
The averaging time for stabilizing the Z position. ...
The averaging time for stabilizing the Z position. Usually, the signal for z-position contains noise, to reduce the noise impacts, z-position is being averaged over this time window.
z_controller_time: (optional) NX_NUMBER {units=NX_TIME}
Time taken by the Z controller to switch mode e.g., feedback off from on and ...
Time taken by the Z controller to switch mode e.g., feedback off from on and vice versa. In this time window, controller fixed its position if feedback changed to off mode.
z_controller_hold: (optional) NX_BOOLEAN
Controller feedback system status: OFF / ON. ...
Controller feedback system status: OFF / ON. The z_controller_hold-field is True, refers feedback system off (mostly case in STS bias spectra) and False refers feedback system on (mostly case in STM constant current spectra).
final_z: (optional) NX_NUMBER {units=NX_LENGTH}
The final Z position of the tip after the scan. ...
The final Z position of the tip after the scan. This parameter is used to indicate any unexpected displacement of the tip.
controller_label: (optional) NX_CHAR
Controller label. This label which will be displayed at places where you can ...
Controller label. This label which will be displayed at places where you can select a channel or controller.
actuator: (optional) NXactuator ⤆
feedback: (optional) NXpid_controller ⤆
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