Hexapods / Stewart Platforms for Astronomy
Commercial Stewart-Gough platform and parallel-kinematic hexapod systems for telescope alignment, active optics, image stabilization, radio telescope instrumentation, and precision observatory applications.
Resolution in large earthbound telescopes is limited by atmospheric turbulence and vibrations. During the last 3 decades PI has designed many large-aperture high-speed tip/tilt systems and hexapod alignment systems for image stabilization and alignment. Piezoelectrically-driven active secondary fast steering mirrors (FSMs) can improve the effective resolution up to 1000% by correcting for these image shifts in real time, especially during long integrations with weak light sources. Today, FSMs are also used for free space optical communication between satellites and on Earth.
More information on fast steering mirrors, hexapods and other precision motion systems for Astronomy.
PI's hexapod 6-axis micropositioning systems are key components for the precise alignment of active mirrors.
PI precision actuators provide superior performance and lifetime and have been used in large telescopes such as the ALMA Telescope in Chile consisting of 60+ Antennas spread across distances of up to 16 kilometers.
PI has designed many hexapods and fast tip/tilt systems for the alignment of mirrors in astronomical telescopes. Talk to a PI engineer for more information.
Active Secondary Hexapod with Tip/Tilt Mirror — NASA IRTF
Active secondary mirror for NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, with a hexapod 6D alignment system.
- Mirror diameter: 244 mm
- Tip/tilt range: ±250 µrad
- Resonant frequency: 490 Hz
More Information on Hexapods and Tip/Tilt Steering Mirror Platforms for Astronomy
Active Secondary Hexapod with Tip/Tilt Mirror — UKIRT
Active tip/tilt mirror for the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, Hawaii, with a secondary hexapod 6D alignment system.
- Mirror diameter: 314 mm
- Tip/tilt range: ±500 µrad
- Resonant frequency: 280 Hz
More Information on 6-Axis Hexapods and Fast Steering Mirrors for Astronomy
Miniature Hexapod for WFIRST Telescope
Custom compact hexapod for prism alignment of the slitless spectrometer for the WFIRST Telescope
Custom Ultra-High-Precision Hexapod for Telescopes / Outdoor Operation
Custom secondary 6-axis hexapod for APEX radio telescopy in Chile.
- Load capacity to 750 N
- Unidirectional repeatability to 5 µm
- Clear aperture Ø420 mm
- Long lifetime: 2 million cycles
- Drive: brushless motors
- Protection class IP64
- Corrosion protection
Video on ALMA (Atacama Large Millimeter Array) radio telescope. PI Hexapod is shown at 0:38.
Compact 6-Axis Motion
Hexapods provide X, Y, Z, pitch, roll, and yaw motion from one compact mechanism instead of a stack of individual linear and rotary stages.
High Stiffness
The payload is supported by six parallel struts, helping provide stiffness and stability for optics, mirrors, sensors, and telescope instrumentation.
Reduced Moving Mass
A common moving platform reduces the cumulative moving mass associated with serial stage stacks, improving dynamic behavior and settling.
| Requirement | Why It Matters in Astronomy | Hexapod Advantage |
|---|---|---|
| Mirror Alignment | Secondary mirrors and active optics require precise angular and linear adjustment. | Software-controlled six-axis alignment with a virtual pivot point. |
| Image Stabilization | Atmospheric turbulence and vibration can shift images during observation. | Fast tip/tilt and multi-axis correction can improve effective imaging performance. |
| Large Payloads | Observatory components can be heavy and difficult to align manually. | Parallel-kinematic designs can position high loads with micron-level precision. |
| Vacuum / Non-Magnetic Needs | Space instrumentation and special scientific systems may require low outgassing or non-magnetic operation. | Vacuum-compatible and piezomotor-based non-magnetic hexapod designs are available. |
Active Mirror Positioning
- Secondary mirror alignment
- Tip/tilt image stabilization
- Active optics correction
Radio Telescope Systems
- Reflector positioning
- Antenna alignment
- Sub-micrometer adjustment under harsh conditions
Scientific Instrumentation
- Spectrograph alignment
- Sensor positioning
- Space telescope and satellite receiving antenna systems
All PI Hexapod systems are designed to be operated by a specialized, yet easy to use vector motion controller. The Hexapod controller allows the user to set a pivot point anywhere inside or outside the Hexapod working space, by a simple software command. This randomized pivot point stays with the platform, no matter how it moves—an invaluable feature for example in optics applications. Moves are specified in Cartesian coordinates and the PC-based controller transforms them into the required motion-vectors for the individual actuator drives. The latest controller generation features flexible interfaces: TCP/IP, for remote / network / Internet addressing or highspeed RS-232.
Learn more about PI hexapods, parallel kinematics, miniature hexapods, high-load hexapods, vacuum-compatible hexapods, and hexapod control software.
Standard HexapodsMiniature HexapodsVacuum HexapodsHigh-Load Hexapods
Additional examples and reference links for hexapod and Stewart-platform applications in astronomy, aerospace, satellite systems, and precision optical alignment.
- PI Hexapod Chosen for LISA Pathfinder Space Mission
- PI Hexapod Stewart Platform Application: Iterative Learning-Based Laser Beam Tracker
- PI Hexapod Stewart Platform Application: Flight-Like Ground Demonstrations of Precision Maneuvers for Spacecraft
- Hexapod Positioning Systems Enable First Image of a Black Hole
- Hexapod Stewart Platform Application Astronomy: Fringe Tracking in the StarLight Formation Interferometer Testbed
- 50 Hexapod Stewart Platforms for ALMA Millimeter Radio Telescope
- One of PI's First Hexapod Alignment Systems in the University of Hawaii 2.2 Meter Fast Tip/Tilt Secondary System
- Hexapod for Satellite Antenna Alignment Control
- Hexapod Alignment System for UKIRT Telescope
- Hexapod for Secondary Mirror Control in SOFIA Telescope
PI is the leading manufacturer of Hexapod high-performance micro- and nanopositioning systems. These parallel-kinematics devices, in a number of different forms, are suitable for diverse applications, ranging from handling systems in electronics fabrication and tool control in precision machining, through medical technology, to optical systems like those found in space telescopes and satellite receiving antennas.
Various models of the powerful parallel kinematic machines (PKM) can move masses of 50, 200 or even 1000 kilograms with micron accuracy as required in their respective applications.
These Hexapod systems are all built with six, high-resolution electro-mechanical or piezoelectric actuators connected to a common platform, similar to flight simulators, yet considerably more precise: in place of hydraulic cylinders, the Hexapods are driven by highly accurate, precision-controlled rotary or linear motors. Different drive principles are employed, depending on the application: Hexapods with piezomotor drives make for a positioning system which is not only vacuum compatible but also completely non-magnetic.