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Glossary open and closed loop postitioning attoMOTION
Open Loop Positioning
In this mode, the positioner is simply driven forward or backward, without an encoder to read back the actual position or a feedback loop to control the desired target position. Many applications don‘ t require either of the latter or provide inherent external means of controlling the position. Still, at least a rough estimate of the actual position can be deduced by counting the number of steps( if the step size can be determined from an external measurement). The step size itself is relatively uniform under fixed conditions( temperature, humidity, pressure, load, etc) and typically within 5 % over the full range but depends strongly on the applied force along the axis. The forward / backward asymmetry is also typically 5 %( no external force assumed).
Closed Loop Positioning
Positioners with an integrated or external encoder(/ RES, / NUM(+), / FPS) can be used for closed loop position control. A feedback loop integrated into the control electronics minimizes the difference between target position and actual position. Setpoints can either be defined in a software interface( ANC350, ECC100) or on the front panel of the closed loop electronics( ANC350). Settling time depends on the resonance frequency of the setup, speed of the feedback loop and measurement bandwidth.
Suitable Controllers
ANC300( open loop)
• modular, up to 7 axes
• suited for scanners and positioners
• USB and Ethernet
• controllable via: LabVIEW | text-based LUA-console | touchscreen
ANC350( closed loop)
• three axes(/ RES, / NUM, / FPS)
• USB and( optionally) Ethernet
• controllable via: LabVIEW | DLL | EPICS Windows Software | touchscreen
ECC100( open & closed loop)
• three axes
• USB and( optionally) Ethernet
• controllable via: LabVIEW | DLL | Windows software attoMOTION
Piezo-based Nano Drives