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Precision In-vacuum MotionIn-Vacuum Piezo motors and encoders
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Precision In-vacuum motion
VG Scienta are pleased to be able to offer a range of in-vacuum precision movements based on a novel design of piezo-electric motors. These motors can be used for open loop control or combined with accurate position feedback systems for closed loop control. Typical application include microscope stages, in vacuum positioning equipment, robotics, and sample stages for HV and UHV applications such as SEM and Auger. The piezo-electric motors offer all the advantages of high resolution and
dynamic performance that is traditionally associated with piezo drives. The
innovative motor design can provide unlimited travel with a wide dynamic
velocity range. The motor operates with no intrinsic magnetic fields and without
any moving parts. High vacuum and ultra high vacuum compatible motors are available.
Linear and rotary motion can be produce depending on the geometry of the coupling
between motor and stage. 
Precision in-vacuum encoders
An essential requirement for precision in-vacuum motion is the ability to accurately determine the position of the sample stage. VG Scienta can also offer a range of UHV compatible encoders that are capable of sub-micron repeatability and accuracy. These encoders, when used in conjunction with the piezo motors described above, permit highly accurate and repeatable movements to be made in a UHV environment. The construction of the encoder scale and read head allow for either linear or rotary (depending on geometry) motion to be encoded. The encoders can also be used in conjunction with other types of drive to provide accurate encoding of position in vacuum. The read heads and scales are bakeable to 100oC and have been fully UHV tested at these temperatures. Control Systems
The motors require a digital drive unit which can run one or multiple motors in parallel (motors can be stacked to give higher forces). If the stage is being operated in closed loop mode the drive works as a velocity amplifier, receiving analogue commands from a standard servo controller. In open loop mode the drive unit can accept signals from a joystick controller to give proportional control of stepped or continuous motion. VG Scienta can also supply all the necessary feedthroughs and connectors, including the fully bakeable D-type connectors, to complete the installation of the motors and encoder systems. | Ultrasonic standing wave motors
The piezo-electric effect in piezo ceramics converts applied electric field to mechanical strain (and vice versa). Under certain conditions of applied field, the ceramic actuators element is made to both extend longditudinally and bend laterally producing an elliptical trajectory at the tip of the ceramic rod. When the motor is coupled via a suitable ceramic running interface to a precision stage, a force is exerted on the stage and linear or rotary motion is produced. The motor operates at frequencies which are typically very much higher than the mechanical resonance of the translation or rotation stage, thus allowing smooth stage motion whilst maintaining high resolution and good positioning accuracy. The motor assembly is pre-loaded against the driven element of the stage. This means that a holding force is generated between motor and stage even when the driving voltage is not applied to the motor. This holding or braking force is applied without causing movement of the stage, unlike external mechanical braking devices. The motors are available in two vacuum grades suitable for HV or UHV service. UHV motors are bakeable to 120°C. 
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