Alar Group Shot 2Aerotech’s ALAR series direct-drive rotary stages provide superior angular positioning and velocity control with exceptionally large apertures. With the combination of a large aperture and direct-drive motor, the ALAR series makes worm-drive large aperture stages a thing of the past.

  • Excellent accuracy and repeatability
  • Cog free motor provides smooth motion
  • No accuracy changes over time from gear wear
Model Aperture Maximum Speed Accuracy Maximum Load Additional information
ALAR Up to 325 mm Up to 300 rpm ±2 arc sec Up to 680 kg View source


Advantage ALAR

Now customers can get large aperture rotary stages with zero backlash and no gear wear or gear vibration as is commonly seen in worm-drive stages. The other added benefit is that direct drive is significantly faster than worm drive, so testing can be completed in less time. In production settings, this equates to faster testing, lower cost manufacturing and higher profits. From the standpoint of system accuracy and repeatability, the stage will maintain its performance over time with no need for maintenance because there are no gears to wear out. With higher accuracy and no backlash, customers can produce more accurate products because their test system is now more accurate.


Applications for the ALAR include single and multi-axis electro-optic sensor testing, missile seeker testing, antenna testing, inertial navigation device testing, photonic component alignment, high-accuracy laser machining and precision wafer inspection. These include testing in vacuum to 10-6 torr. These rotary stages can also be configured as multi-axis gimbals.

High Speed

ALAR stages can operate between 45-300 rpm, depending on the particular model selected. This speed range is significantly higher than gear-drive stages of similar size.

Superior Mechanical Design

Angular contact bearings are used to maximize performance with respect to tilt error, moment stiffness and rotating friction. A precision-machined shaft further minimizes tilt error. The design incorporates integral connections that minimize cable issues. The ALAR works especially well in applications that require 360° continuous motion but have limited space. The stage is 65-160 mm tall and provides smooth motion without travel restrictions.

Brushless Direct-Drive

To maximize positioning performance, the ALAR series utilizes Aerotech’s brushless, slotless motors. This motor has all of the advantages of a brushless direct-drive motor – no brushes to wear, no gear trains to maintain and high acceleration and high speeds. Since it is a slotless, ironless design, there is zero cogging, meaning there is absolutely no torque ripple. This makes the ALAR ideal for applications requiring outstanding contoured motion, smooth scan velocity or precise incremental steps.

High Payload Capacity and Large Moment Load Stiffness

The ALAR comes in two different configurations. The standard profile (SP) unit has high payload capacity and high moment load stiffness so it can handle applications where its rotation axis is parallel or perpendicular to gravity and the payload center of gravity is cantilevered away from the stage. The low profile (LP) unit has high payload capacity and is good for applications where the axis of rotation is parallel to gravity. Both the SP and LP units have the same aperture options and motor options. Either SP or LP stages can handle between 260-1300 lb of axial load.

Accurate Positioning

Performance is assured with encoder line counts from 31000 to 76800 per rev, resulting in resolutions from 0.02 arc sec/count to 0.009 arc sec/count. The motor and high-performance rotary encoder are directly coupled to a common shaft. The absence of gear trains and mechanical couplings means no position errors caused by hysteresis, windup or backlash. As a result, accuracy of ±2 arc sec and bi-directional repeatability of ±0.5 arc sec is attainable.ALAR2

Flexible Configurations

Aerotech manufactures a wide range of servo amplifiers and advanced controllers to provide a complete, integrated package.

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