Aerotech’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.
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 multiaxis 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 multiaxis gimbals.
Conventional worm-drive rotaries with similar apertures and payload capacity only operate to 15 rpm or less. These direct-drive stages have been tested to 85 rpm continuous rotation – over 5 times faster than worm drives.
Superior Mechanical Design
Angular contact bearings are used to maximize performance with respect to wobble, moment stiffness, and rotating friction. A precision-machined shaft further minimizes wobble. 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.
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 300-1000 lb of axial load.
Performance is assured with encoder line counts from 31000 to 74000 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 ±3.9 arc sec and bi-directional repeatability of ±0.5 arc sec is attainable.
Aerotech manufactures a wide range of servo amplifiers and advanced controllers to provide a complete, integrated package.
1. This is the fundamental encoder resolution before multiplication or quadrature. With Aerotech controls, divide the resolution by 1000X to 8000X to get actual available resolution – i.e., 10 arc- sec fundamental = 10/8000 = 0.00125 arc sec actual usable resolution.
2. The ALAR-LP base must be fully supported by a rigid mounting plate to achieve this moment load.
3. Accuracy assumes calibration.