ALAR-XP Large Aperture Rotary Stages


Design Features

  • High torque output up to 1100 N•m
  • Excellent accuracy, repeatability, and minimum incremental motion
  • Clear-aperture diameters of 250 mm or 325 mm
  • Direct-drive torque motor delivers extremely precise, smooth, cog-free rotation
  • Long service life and consistent performance over time
  • High axial-, radial-, and moment-load capacities support large payloads and gimbal configurations
  • Engineered for easy integration into multi-axis systems and machines
  • Incremental and absolute encoder options contribute to excellent accuracy and repeatability
Aerotech’s ALAR family of direct-drive rotary stages provides superior angular positioning and velocity control. ALAR-XP offers extremely high torque output, high load capability, and smooth, precise rotation. It is suitable for use in both vertical
and horizontal applications. Other members of the ALAR series include the ALAR-LP, with an ultra-low profile, and the ALAR-SP, which offers a balance of load capability, torque, and form factor.

Advantage: ALAR

ALAR-XP offers numerous advantages over worm-drive stages. Because ALAR stages use direct-drive torque motors, they are free from backlash, vibration, and excessive wear commonly associated with gear-driven stages, and they are also capable of much higher speeds and accelerations. These advantages translate to higher system accuracy, repeatability, and longevity, as well as greater throughput. Users can more precisely manufacture, inspect, or process more parts in less time, leading to lower operating costs and higher profits.

Brushless, Slotless Direct-Drive Motors

Aerotech’s brushless, direct-drive motors are featured in all ALAR stages. Because there are neither brushes to wear, nor gear trains or couplings to maintain, ALAR stages are capable of high speeds and accelerations, plus consistent, stable performance over time with zero backlash, windup, or hysteresis. Further, ALAR
motors are both slotless and ironless, thereby eliminating cogging and torque ripple to deliver exceptionally smooth motion. ALAR stages are ideal for applications requiring outstanding contoured motion, smooth scan velocities, and precise incremental steps.

Extreme Torque, Precision Rotation

ALAR-XP motors are based on Aerotech’s powerful BLMX-series, which deliver the highest force output of any commerciallyavailable brushless, slotless, ironless motor. Traditional highertorque solutions typically involve either gear trains or slotted, iron-core motors, which are both detrimental to achieving
high-precision positioning and velocity performance. ALAR-XP is a game-changer because it enables users to achieve high torque output without compromising the quality of motion. Eliminating the need to make the trade-off between torque and precision allows systems designers.

Flexible Configurations for Simplified Integration

ALAR-XP is offered with features and options that facilitate easy integration into multi-axis motion systems and subsystems. It is available with clear-aperture diameters of 250 mm or 325 mm, and also a variety of feedback options including analog 1 Vpp, digital RS422, and absolute encoders. Continuous 360-degree
travel is standard, with available limited-travel options ranging from 10 degrees to 340 degrees. For each model, there are two motor options depending on the amount of torque needed. ALAR-XP stages can even be adapted for use in vacuum environments.


Common applications for ALAR-XP stages include single- and multi-axis sensor testing, missile seeker testing, antenna testing, inertial navigation device testing, opto-electronics alignment and testing, and high-accuracy laser machining. ALAR-XP stages can also be configured as multi-axis gimbals. The large-diameter clear
aperture and powerful direct-drive motor make ALAR-XP a betterperforming
alternative to more traditional worm-gear stages or even direct-drive stages with slotted iron-core motors, especially for applications requiring both high torque output and ultraprecise motion.


ALAR-XP Specifications

Mechanical Specifications






Continuous (optional 340° max. limited travel)


250 mm

325 mm

Resolution (Min. Incremental Motion)1

0.05 µrad (0.01 arc sec)

0.04 µrad (0.009 arc sec)


± 9.7 µrad (± 2 arcsec)

Bidirectional Repeatability

± 2.4 µrad (± 0.5 arc sec)

Tilt-Error Motion

9.7 µrad (2.0 arc sec)

Maximum Speed3,4

180 rpm

100 rpm

Maximum Torque

548.6 N•m

731.5 N•m

833.0 N•m

1110.7 N•m

Continuous Torque

64.2 N•m

85.6 N•m

107.4 N•m

143.1 N•m

Axial Load

4950 N

5825 N

Radial Load

5200 N

6650 N

Moment Load

1825 N•m

2650 N•m

Shaft Inertia

0.89 kg•m2

1.71 kg•m2

Shaft Inertia with Limits

0.96 kg•m2

1.82 kg•m2

Stage Mass

100 kg

104 kg

125 kg

130 kg

Stage Mass with Limits

104 kg

108 kg

129 kg

134 kg

  1. Resolution assumes -AS encoder with 2000x controller multiplication.
  2. Certified with each stage. Requires the use of an Aerotech controller.
  3. Maximum speed assumes a bus voltage of 320 VDC.
  4. Digital RS422 encoder options will limit maximum speed below the listed value. Contact factory for specific stage and encoder speed combination.

Electrical Specifications

Electrical Specifications






Brushless Slotless

Continuous Current











Peak Current, Stall











Bus Voltage

Up to 340 VDC

Incremental Encoder Line Count

64,800 lines/rev

76,800 lines/rev

Limit Switches1

5 V, normally closed

  1. Limited travel options only.


Ordering Information

ALAR-XP Large-Aperature Rotary Stage

ALAR250XP Mechanical-bearing, direct-drive rotary stage, high torque, 250 mm aperture
ALAR325XP Mechanical-bearing, direct-drive rotary stage, high torque, 325 mm aperture

Motor (Required)

-M1 Standard motor
-M2 High-power motor

Travel (Required)

  Continuous travel (standard)
-TR010 Limited travel, ±5 degrees
-TR020 Limited travel, ±10 degrees
-TR030 Limited travel, ±15 degrees
-TR060 Limited travel, ±30 degrees
-TR090 Limited travel, ±45 degrees
-TR120 Limited travel, ±60 degrees
-TR180 Limited travel, ±90 degrees
-TR240 Limited travel, ±120 degrees
-TR300 Limited travel, ±150 degrees
-TR340 Limited travel, ±170 degrees

Feedback (Required)

-E1 Incremental encoder, 1 Vpp
-E6 Incremental encoder, digital RS422, x200 interpolation
-E7 Absolute encoder

Integration (Required)

Aerotech offers both standard and custom integration services to help you get your system fully operational as quickly as possible. The following standard integration options are available for this system. Please consult Aerotech if you are unsure what level of integration is required, or if you desire custom integration support with your system.

-TAS Integration - Test as system
Testing, integration, and documentation of a group of components as a complete system that will be used together (ex: drive, controller, and stage). This includes parameter file generation, system tuning, and documentation of the system configuration.
-TAC Integration - Test as components
Testing and integration of individual items as discrete components that ship together. This is typically used for spare parts, replacement parts, or items that will not be used together. These components may or may not be part of a larger system.