- OEM / SystemsOEM Systems | Precision Components | Automation Sub-SystemsPI offers 1000’s of proven, off-the-shelf precision motion products that can be quickly modified for the OEM or into a custom automation sub-system.
- Meeting the Demands of OEMsOEM Systems | Precision Components | Automation Sub-SystemsPI has a long track record of working with OEMs in the most demanding industries from Semiconductor Technology to Medical Design – industries where product performance, quality, and the ability to ramp up quickly are not the only parameters required to satisfy the customer's demands. Working with technology leaders all around the world forces you to continuously improve your yield, process, and product performance. And unless your quality is outstanding, you cannot become a key supplier to major US, European, and Japanese companies in the Optics, Photonics, Semiconductor, and Automotive industry.
- Engineered Motion / Automation Sub-SystemsPrecision Automation Solutions | Engineered SystemsPI is a supplier of high-end precision motion systems and makes use of own drive components and high-precision positioners to build customized positioning and automation sub-systems —“motion engines”—for our customers. With the largest portfolio of precision motion technologies in the industry, PI engineers have the best foundation to find a solution that matches your requirements in terms of precision, quality and budget – in a timeframe that works for you.
- Meeting the Demands of OEMs
- ProductsPrecision Motion Technologies | Positioning SystemsOverview of the Broadest & Deepest Portfolio of Precision Motion and Automation Technologies from Piezo to Air Bearings and Linear Motors
- Products: Overview, New, Finder, ShopFind Precision Positioning Solutions Quickly - Product Finder | PI USAWith thousands of standard products and customization available, PI has the motion control positioning product solution for your application.
- Products OverviewProducts OverviewOverview of the Broadest & Deepest Portfolio of Precision Motion and Automation Technologies from Piezo to Air Bearings and Linear Motors
- New ProductsNew Motion Control & Precision Positioning Products | PI USALearn about the latest innovations in motion control and nanopositioning components and systems.
- Product FinderUse the PI Product Finder - it's fast and easy!Select the product type specified by the axes of motion required. Selection of more criteria expands or shortens the list of results. Select more than one filter at at time, for example, to find positioning stages designed for higher load capacity, too.
- ► Shop► ShopShop for select PI products online
- Products Overview
- Air Bearings & Ultra High Precision StagesAir Bearing Stages | Motorized | Linear | RotaryAir bearings provide advantages over mechanical bearings when vibration-free motion is required, highly constant velocity control is crucial, and when angular repeatability and geometric performance must be optimal. Air bearing stages (linear, rotary, and spherical) replace mechanical contact by a thin air film, avoiding wear, friction, vibration, and hysteresis effects.
- Miniature Positioning StagesMiniature Positioning Stages | Supplier | ManufacturerCompact positioning stages are crucial for the miniaturization process in cutting-edge research and industrial applications, for test & measurement, optical and opto-mechanical alignment, and component assembly. PI provides the largest portfolio of miniature stages, including high-speed linear motor stages, economical stepper motor units, and ultra-compact piezo motor positioners.
- Motorized Stages: Linear, Rotary, XYMotorized Stages | Positioning | ManufacturerPI offers the broadest and deepest range of precision motion technologies for micro and nano precision applications. Our engineers work with our customers to find the best drive and bearing technology for each individual application. Having access to multiple drive and positioning technologies allows an open discussion with a better outcome for the customer.
- Overview - Motorized Linear/Rotary StagesOverview - Motorized Linear/Rotary Stages
- Linear StagesLinear Stages - Precision Positioning Solutions | PI USASeveral types of motorized precision linear translation stages | PI USA
- Fast Linear Motor Stages and ActuatorsOverview: Linear Stage, Linear Motor Driven, Fast Brushless Motor Positioning Stages | PI USABrushless linear motor-driven stages provide high speed, precision and long life.
- Z-Stages (Vertical Motion)Vertical Linear Stages – Precision Motorized Z-Positioners | PI USA
- XY StagesXY Stages – 2-Axis Motorized Precision Positioning Stages | PI USASeveral types of planar XY stages: Direct-driven stages, ball-screw stages and air bearing planar XY stages
- XYZ StagesXYZ Stage - Multi-Axis Precision Motorized Stages
- Rotary Stages / GoniometersPrecision Rotation Stage, High Resolution Rotary Positioners, Rotation Tables, Goniometers, by PI USASeveral types of motorized rotation stages: Direct-driven stages, ball-bearing stages and air bearing stages
- Heavy Duty Stages / Industrial AutomationHigh Speed / Performance Positioning Stages for Automation - Linear Stages | Rotary Stages | PI USAHigh performance motorized stages, designed for heavy duty applications in industrial precison automation.
- Sub-Systems for AutomationSYS > Engineered Motion/Automation Sub-SystemsThe PI group employs over 1,200 people in 15 countries and runs engineering and manufacturing centers on 3 continents. Select from the broadest portfolio of precision motion technologies, including piezoelectric and air bearing systems, with 1,000’s of standard products or have our engineers provide you with a custom solution.
- Overview - Motorized Linear/Rotary Stages
- Linear ActuatorsActuators | Precision | Linear | Actuator SystemA precision linear actuator is a positioning device that provides motion in 1 degree of freedom. PI designs and manufactures a variety of precision linear actuators (pushers) including economical stepper-motor driven actuators, high-speed linear motor types for automation and nanometer precise piezo-motor actuators.
- Gantries / Cartesian RobotsGantry Stages | Gantries | Cartesian RobotA gantry precision positioning stage is sometimes called a linear robot or Cartesian robot. Gantries typically provide motion in 2 or 3 linear degrees of freedom (X-Y and X-Y-Z) and are often used for pick and place applications, 3D printing or laser machining, and welding applications.
- 6-Axis Hexapods / Parallel PositionersHexapod Positioner | Six DOF | Stewart PlatformsHexapod positioners are often referred to as Stewart Platforms. A hexapod is based on a 6-axis (XYZ, Pitch, Roll, Yaw) actuator system arranged in parallel between a top and bottom platform. PI parallel kinematics (PKM) precision positioning systems have many advantages over serial kinematics stages, such as lower inertia, improved dynamics, smaller package size and higher stiffness. In addition hexapods are more flexible than conventional 6 axis positioners.
- 6-Axis Hexapods / Parallel Positioners6-Axis Hexapods / Parallel Positioners
- Control of Hexapod / Stewart Platforms: Hexapod Motion Controllers & Simulation Software6DOF Motion Platforms | Hexapod Controllers & Simulation Software | Stewart Platform | ManufacturerControllers, software and accessories for Hexapod Stewart platforms and parallel kinematic motion systems | PI USA
- 6-Axis Hexapods / Parallel Positioners
- Piezo Flexure Nanopositioning StagesNanometer Precision: Piezo Stages for Nanopositioning, Piezo Nanopositioners, Piezo Flexure Scanning Stages | PI USAPI offers the broadest and deepest portfolio of nanometer precision motion technologies, from piezo-driven nanopositioning and scanning stages to motorized 6-axis hexapod positioning systems.
- Overview - Piezo Flexure StagesOverview - Piezo Flexure Stages
- Linear Piezo Flexure StagesLinear Piezo Stages for Nanopositioning – Flexure-Guided Precision NanoPositioners | PI USALargest selection of frictionless, high performance piezo-stack-driven flexure linear nanopositioning stages | PI USA
- Vertical & Tip/Tilt Piezo StagesPiezo Z-Stage, Piezo Z-Tip-Tilt Platform. Flexure Guided Nanopositioning Stages| PI USALarge selection of Piezo Z-Stages and Tip/Tilt scanners with nanometer precision | PI USA
- Fast Steering Mirrors & Tip/Tilt PlatformsPiezo Steering Mirrors | Active Optics
- Nanofocus Lens ScannersFast Piezo Focus Lens Positioners and Scanners – Piezo Flexure Guided Precision Positioners | PI USALargest Selection of Nano-Focus drives for microscope lenses – flexure-guided precision positioners
- XY Piezo Flexure StagesPiezo Stages | XY | Nanopositioning StagesLargest selection of integrated XY piezo flexure stages with nanometer precision.
- XYZ Piezo Flexure StagesXYZ Piezo Nanopositioning Stages – Flexure Guided 3-Axis Precision Positioners | PI USALargest selection of integrated XYZ piezo flexure stages with nanometer precision.
- 6-Axis Piezo Flexure Stages6-Axis Piezo Nanopositioning Stages – Flexure Guided Precision Positioners | PI USAPiezo-driven fast steering mirrors (FSM) achieve nanoradian resolution and high bandwidth.
- Tutorial - Piezo NanopositioningNanometer Precision: Nanopositioning Basics Tutorial. Piezo Nanopositioners, Scanning Stages, Flexure Guided Positioners | PI USAThere are several ways to achieve nanometer precision motion. The best positioning systems avoid friction all together, in both the drive system (motor) and in the guiding system (bearings). Frictionless bearings also avoid the bearing rumble caused by balls and rollers and provide vibration-free motion with highly constant velocity.
- Overview - Piezo Flexure Stages
- Piezo Motors: Stages & ActuatorsPiezo Motors | Linear Motor Positioners | ManufacturerPiezo Motors are intrinsically vacuum compatible, non-magnetic and self locking at rest, providing long travel compared to traditional piezo mechanisms. The individual drive concepts are optimized for different applications, they differ in their design, size, cost, force & speed and other performance parameters.
- Overview - Piezo Motors (Stages/Actuators)Overview - Piezo Motors (Stages/Actuators)
- Actuators with Piezo MotorsCompact precision linear actuators stages with several types of piezo motor drives – ultrasonic, stick-slip, piezo-walk, piezo-ratchet. | PI USA
- Linear Stages with Piezo MotorsPrecision linear stages with several types of piezo motor drives – ultrasonic, stick-slip, piezo-walk, piezo-ratchet. | PI USA
- XY Stages with Piezo MotorsXY piezo motor linear stages with several types of precision piezo motor drives – ultrasonic, stick-slip, piezo-walk | PI USA
- XY Piezo Flexure StagesXY Piezo Flexure StagesHigh-precision 2-axis nanopositioning systems integrate PICMA® piezo actuators for maximum reliability. Repeatable, drift-free positioning with optimal stability is possible by the use of high-quality nanometrology sensors.
- Rotary Stages with Piezo MotorsRotary piezo motor stages with several types of precision piezo motors– ultrasonic, stick-slip (inertia), | PI USA
- Tutorial - Piezo Motion ControlWhy All Piezo Motors are NOT Created Equal: The piezoelectric effect for precision motion control - PI Physik Instrumente.The demand for higher speed and/or precision in fields such as bio-nanotechnology, semiconductors, metrology, data comm, and photonics keep pushing manufacturers to come up with innovative drive technologies.
- Overview - Piezo Motors (Stages/Actuators)
- Piezo Transducers & ActuatorsPiezo Actuator | Piezo Transducer | ManufacturerPiezoelectric translators (transducers) are precision ceramic actuators which convert electrical energy directly into linear motion with high speed, force and virtually unlimited resolution. These actuators are used in every modern high tech field from semiconductor test & inspection to super-resolution microscopy, bio-nanotechnology and astronomy/aerospace technology.
- Piezo Actuators & Transducers: Stacks, Chips, Benders, Tubes, Spheres, Shear…Piezo Actuators & Transducers: Stacks, Chips, Benders, Tubes, Spheres, Shear…
- Value-Added Piezo Transducers & Piezo AssembliesValue Added Piezo Assemblies: Transducers, Actuators, Sensors, Manufactured by PI CeramicDeveloping and manufacturing piezo ceramic materials and components are complex processes. PI Ceramic - PI’s piezo material design and manufacturing facility - boasts several decades of experience as well as the right tools for rapid prototyping of custom engineered piezo components and assemblies. From the formulation of advanced piezo materials to the processing steps such as cutting, milling, grinding, and the precision assembly, every stage is controlled by our engineers and product specialists.
- Piezo Ceramic ComponentsPiezo Ceramic Components
- Piezo Actuators & Transducers: Stacks, Chips, Benders, Tubes, Spheres, Shear…
- Microscopy, Bio-Imaging, Life SciencesHigh Precision Microscope Stages, Piezo Lens Scanners, Tools for Bio-Imaging | PI-USAPiezo nano-positioning stages are essential tools for high-resolution microscopy, such as Super Resolution Microscopy or AFM. Their sub-atomic resolution and extremely fast response allow researchers to create higher-quality images faster. PI provides a large variety of fast Z-Stages and collar piezo objective positioners for 3D imaging (Z-stack acquisition), deconvolution, and fast focusing applications.
- Stages for Microscopy & Bio-ImagingStages for Microscopy & Bio-Imaging
- Applications: Life Sciences / MedicalPrecision motion control for medical engineering and life sciences applications | PI USA
- Stages for Microscopy & Bio-Imaging
- Photonics Alignment SolutionsActive Photonics Alignment | Optics Alignment | SolutionsPI provides a variety of innovative fiber alignment systems from motorized fiber positioners to automated optic and photonic alignment such as used in telecommunication, data commumication and for packaging / automation. In addition to fiber-based applications, fast steering systems for free-space-optical communication are also available. Products range from motorized 6D micromotion alignment systems for industrial photonics automation, through ultra-fast piezoelectric scanning & alignment modules to modular devices with manual control for laboratory test setups. All motorized systems come with extensive software for easy setup and integration.
- Vacuum Positioning Stages & ActuatorsVacuum / UHV Compatible Stages - Linear & Rotary Positioners for Vacuum, Wide Temperature Ranges | PI USAPI miCos has extensive experience in the design and manufacturing of vacuum and high vacuum compatible precision optomechanical positioning equipment for low temperature and wide temperature ranges. We provide translation stages, vertical linear stages, rotation stages, XY stages and complex multi-axis positioning systems in vacuum spec.
- VacuumProduct Series with Vacuum-Ready ItemsPI offers specific catalogue items for selected product series that are already suitable for high vacuum (HV) or ultra-high vacuum (UHV).
- Vacuum
- Controllers, Drivers, Motion SoftwareMotion Controllers, Piezo Drivers-High Voltage Amplifiers, and Motion Software Overview | PI USA
- Overview - Controllers & Motion SoftwareOverview - Controllers & Motion Software
- Piezo Controller, Driver, Nanopositioning Controller, High-Voltage Amplifier, Piezo Power Supply by PI USAPiezo Drivers | Piezo Motion Controllers | ManufacturerA piezo controller or driver is used to control the motion of a piezo positioning device. There are open and closed loop controllers. Open-loop controllers are often referred to as piezo driver or even piezo power supply. Closed-loop controllers are divided in two basic types: analog-servo and digital servo controllers.
- Controllers/Drivers for Motorized StagesMotion Controller | Drivers | Positioning SystemsPI provides a large variety of hardware & software solutions for high precision motion control. Our portfolio spans from integrated compact single axis servo controllers / drivers, such as popular Mercury-class motion controllers, to complex multi-axis systems for parallel-kinematics positioners, such as hexapods.
- ACS Motion ControlACS Motion Control for Industrial AutomationWe recommend the controllers of our partner, ACS Motion Control especially for automation with industrial standards. Ask us about your integrated solution!
- Software - Motion Control SoftwareMotion Control Software | Software Tools | Positioning SolutionsFor LabView, C++, VB, Matlab, Image Acquisitiong Packages, NI DAC Cards, ..... PI provides high-level, robust, easy-to-use software tools for fast, seamless integration of motion systems into application control software.
- Overview - Controllers & Motion Software
- Capacitive SensorsNanometer Resolution: Capacitance Sensors for Nano-Measuring, Nano-Metrology | PIA capacitive sensor is a proximity sensor that detects nearby objects by their effect on the electrical field created by the sensor.
- Accessories: Plates, Brackets, CablesAdapters and Cables for PI Precision Motion ComponentsStandardization is common with adapter plates and brackets, but we can create a custom accessory to fit your application system. PI products ship with the required cables. Customization is always an option.
- Products: Overview, New, Finder, Shop
- Tech BlogPI Blog / Tech Articles on Advancements in Precision Motion Control, Automation and Piezo Technology | PI USAPI’s tech blog offers 50 years of insight into innovative applications of precision motion control, nanopositioning, and micropositioning in industry, science, and research. We hope the PI blog is an enjoyable and informative resource, and a starting-point for innovation across disciplines.
- Resources
PI – Resources – Papers, Videos, ISO9001, Service, DownloadsFind Tech Articles, Videos, Papers, Brochures, Software Information, ISO9001 Certificates and more.- Ask an Engineer (direct email request)Ask an Engineer (direct email request)
- User Manuals, Software, WhitepapersUser Manuals, Software, WhitepapersFind product documentation & software, catalogs & brochures, whitepapers & success stories.
- Catalogs & BrochuresDownload Catalogs on Precision Motion Control and Nanopositioning ProductsFind brochures and catalogs for download.
- ISO 90001 CertificatesISO 90001 CertificatesView PI's active ISO certificate
- Metric Tolerances & Thread PitchMetric Tolerances & Thread PitchView metric tolerances and thread pitch classifications
- Motion Control SoftwareMotion Control SoftwarePI provides high-level, robust, easy-to-use motion control software tools for fast, seamless integration of motion systems into application control software. Supported programming languages and applications include LabView, C++, VB, Matlab, Image Acquisitioning Packages, NI DAC Cards, ...
- News & EventsNews & EventsFind PI press releases, enews, and tradeshow exhibit schedule where you can get free advice from a PI Engineer.
- SeminarsFree Seminars on Precision Motion Control / Automation – Motorized and Piezo-Based Solutions | PI USA
- ServicePI – Global Customer Services
- On-Site ServicesOn-Site ServicesThe PI Global Services Division (GSD) is a team of PI skilled after-sales support engineers located around the world, dedicated to providing world class customer support.
- Extended WarrantyExtended Warranty
- Ask an EngineerAsk an EngineerQuickly receive an answer to your question by email or phone from a local PI sales engineer.
- Request ServiceRequest ServiceQuickly receive an answer to your question by email or phone from a local PI sales engineer.
- DownloadsDownloadsFind interesting downloads: Product documentations, brochures, catalogs, certificates, success stories, whitepaper and PI Update Finder.
- Expert Consultancy from PIExpert Consultancy from PIIf our customers need to solve a complex problem, they often require individual advice. We are happy to come and advise you on site.
- On-Site Services
- Tech BlogTech BlogPI’s tech blog offers over 40 years of insight into innovative applications of precision motion control, nanopositioning, and micropositioning in industry, science, and research. We hope the PI blog is an enjoyable and informative resource, and a starting-point for innovation across disciplines.
- Technical Papers / WhitepapersTechnotes & Whitepapers / Application Articles: Piezo / Micro- / Nanopositioning Motion Control: Technical Research PaperPI precision motion and positioning solutions have helped customers in many industrial fields and research laboratories to achieve their goals faster. Feel free to download the papers below.
- Videos & AnimationsVideos on Motion Control and Positioning Technologies | PI USAWatch videos, animations and practical applications of PI products, systems, components
- WebinarsWebinarsWebinar topics include piezo mechanisms, adaptive machines, automation manufacturing advancements, photonics assembly & packing concepts.
- Apps/Tech
Technologies and Applications for Precision Motion Components and Sub-Systems | PI USAPI products are often used at the cutting edge of technology. They solve critical motion problems in lithography, microscopy, astronomy, laser technology, photonics and semiconductor manufacturing on locations around the world and in places as remote as the Science Lab on the Mars Rover.- News/Events
PI - Webinars On-Demand, Company Announcements, New Products for Precision Motion ControlStay up-to-date with the latest PI news, view our webinars on-demand, see product demos or virtual tradeshows, or connect with a PI engineer.- News & EventsNews & EventsStay up to date with the latest PI news, or plan on talking to a PI engineer at a tradeshow.
- Product DemosProduct DemosFrom 3D printing to photonics alignment, from industrial automation to in vitro diagnostics
- WebinarsMotion Control On-Demand WebinarsWebinar topics include piezo mechanisms, adaptive machines, automation manufacturing advancements, photonics assembly & packing concepts
- Virtual Trade Show StandsWelcome to Our Virtual Trade Show Stands!We would be pleased to welcome you personally at our exhibition stands all over the world. In addition, we also invite you to our virtual trade show stands - be inspired by our application solutions!
- About
About PI USA: Custom design & service / export controlled applications & ITAR RegisteredPI (Physik Instrumente) provides the broadest and deepest portfolio of precision motion technologies in the world. PI USA complies with the US laws for export controlled technologies.- AboutAbout PI USA / Custom design & service / export controlled applications & ITAR RegisteredPI (Physik Instrumente) provides the broadest and deepest portfolio of precision motion technologies in the world. PI USA complies with the US laws for export controlled technologies.
- Online Contact FormOnline Contact FormLooking for product information, datasheets, CAD files? Want to have a brainstorming consultation? Need an RMA? Have questions about your order? Request a catalog? Contact us! We're here to help you.
- Directions to PI USA OfficesDirections to PI (Physik Instrumente) USA Offices – Global Leader in Precision Motion Control Solutions
- Ask an Engineer (direct email)Ask an Engineer (direct email)Talk to our engineers first. They have access to in-depth knowledge and test data on diverse driving and guiding technologies, spanning from electromagnetic to piezoceramic and from mag-lev to air bearings. They also have experience selecting the right technology for each individual application. Often an adaptation of existing technologies/products will suffice to solve a problem. However, experience along with detailed knowledge and PI’s significant R&D investment in new technologies enables our engineers to take unique approaches.
- Request a SeminarRequest a Seminar
- News & EventsNews & Events
- CareersCareers at PI - Join the Global Leader in Precision Motion & Positioning TechnologiesPI offers sound training in technical and business careers with a future. Pupils, students, graduates and professionals can get involved at PI and will be supported by us in their professional and personal further development.
- ITAR / Export Controlled ApplicationsPI-USA: ITAR registered, motion control for defense applications, security, COTS, custom US based design, by PI USA
- Test & Metrology / Manufacturing Equipment / CleanroomsLearn what Nano-Metrology Equipment is Used to Test High-Performance Motion & Positioning Systems
- Test & Metrology / Manufacturing Equipment / Cleanrooms OverviewTest & Metrology / Manufacturing Equipment / Cleanrooms Overview
- Manufacturing in Cleanrooms at PIManufacturing in Cleanrooms at PIPI has the capability to manufacture and qualify products under cleanroom conditions, which is extended and improved continually according to market needs.
- Fractal Manufacturing Structure at PIFractal Manufacturing Structure at PIPI manufactures in autonomous organization fractals. Each unit is responsible for its own product line, has all the necessary skills and production equipment.
- Test & Metrology / Manufacturing Equipment / Cleanrooms Overview
- Watch PI Product Videos on YouTubeWatch PI Product Videos on YouTubeUse PI product videos as a resource for how you can apply our precision motion control technology to your application. Then, talk to a PI Engineer about how to make it happen.
- Connect with PI on LinkedInConnect with PI on LinkedInConnect with PI USA on LinkedIn
- Follow PI on TwitterFollow PI on TwitterFollow PI on Twitter
- PI WorldwidePI WorldwideThe PI Group represented by subsidiaries and dealers all over the world. Check here to find your local contact!
- Ask an Engineer
Get Help from a PI Engineer*Save Time & Headaches – Get Free Advice from a PI Engineer* Tap into our engineers’ collective knowledge base – not only is it free, but it also saves hours of your valuable time while preventing plenty of headaches in the future.- Contact
ContactLooking for product information, datasheets, CAD files? Want to have a brainstorming consultation? Need an RMA? Have questions about your order? Request a catalog? Contact us! We're here to help you.- Shop
ShopShop for select PI Motion Control, Positioning and Piezo Solutions products online- Buy Motion Control, Positioning and Piezo Solutions OnlineBuy Motion Control, Positioning and Piezo Solutions OnlineShop for select PI Motion Control, Positioning and Piezo Solutions products online (select products)
- 0Quote list
- Search
1. Introduction
Astronomical telescopes usually employ active position control for primary mirror surfaces using motorized mechanical actuators. The motion needed is generally quasistatic, to compensate gravitational and thermal effects. Another application for precision actuators within the telescope at a significantly faster motion response is the high speed tip/tilt control of a secondary or tertiary mirror.
Fig 1.1 Weatherproof Hexapod for astronomy application (Image: PI) Fig 1.1 shows a typical 6-axis hexapod positioner designed for secondary mirrors. It performs micron level positioning using high precision motorized components, and some designs have integrated piezoelectric actuators for rapid tip -tilt movements of the secondary mirror.
Fig 1.2 Design of a classical motorized actuator (Image: PI) The classical design for a motorized actuator consists of a DC motor with an encoder, gears, and a leadscrew nut assembly to convert the rotary motion to linear translation. The achievable performance depends, for the most part, on the choice of mechanical components and the control algorithms. The physical size and mass of the actuation system is load dependent and for primary mirror applications often include counterbalancing mechanisms for offloading the motion drives. With high precision gears and leadscrews (e.g., Harmonic Drive gearheads, zero backlash ball, and roller screws) position resolutions of 0.1 to 0.5 µm can be achieved. The resolution can be bettered by adding a piggy-back piezo actuator with a high-resolution linear encoder, or by using motion deamplification techniques at the expense of added complexity and part count. All applications mentioned above require minimal energy consumption during operation for thermal control. An essential requirement then is that the units be self-locking when not under power, something which has required the addition of a brake acting on the leadscrew or motor for classical mechanical actuators. However, friction, play, and the associated manufacturing tolerances of the mechanical components limit the achievable position resolution in motorized actuator technology.
Fig 1.3 Design of PiezoWalk actuator (Image: PI) 2. The Development of NEXLINE® Technology
Piezoelectric ceramic actuators however, acting as solid-state analog positioning elements, are not subject to these limitations. Piezo actuators can achieve extreme reliability and lifetime. An example is the NASA/JPL test of the PICMA® multilayer actuators form the Mars Mission. Here actuators were submitted to 100 billion cycles of life testing and survived without failures. For more information: Piezoelectric multilayer actuator life test and Precision Motion and Positioning Equipment on Mars Rover Curiosity – Still Going Strong.
The resolution of a piezo actuator is limited only by the noise on the control signal and is typically in the nanometer or picometer range. However, the displacement available with the piezo effect is limited to 0.1%-0.2% of the length of the piezo ceramics block. The implementation of piezo actuation to longer displacement (many millimeters) with high force has been very problematic over the years with vibrational/acoustic noise, low force, and low reliability from high wear rates as major technological hurdles. The motivation behind the development of NEXLINE® drives therefore was to provide the advantages of piezo actuators over long travel ranges while overcoming the technological hurdles mentioned above in a compact modular actuator.
Fig 2.1 Polarization and displacement direction in a composite stack of shear and linear piezo plates (Image: PI) 2.1 Dither Mode Operation
A NEXLINE piezoelectric step drive consists of an arrangement of piezoelectric elements polarized in different directions. Shear piezo elements, highly preloaded against the runner, drive it perpendicular to the interface in a direction which depends on whether their control voltage is rising or falling. See Fig 2.2 and 2.2a.
Fig 2.2 Dither mode of operation (Image: PI) In dither operating mode, all the drive piezos are operated in parallel and the stiffness and drive force can be scaled by increasing their number. Extremely high resolutions (picometer level) and high operating bandwidths can be achieved. However, the travel range available in this mode is limited from 5 to 8 µm, yet it is able to provide interferometric class position resolution for heavy optical surfaces or components.
2.2 Slew Mode Operation: Step and Constant Velocity Mode
In order to overcome the travel-range limitation of dither mode, each shear piezo is bonded to a longitudinal piezo which provides a clamp/unclamp effect. When a clamping piezo retracts, its shear piezo lifts off the runner. The clamping piezos are driven in two groups 180° out of phase. This makes it possible to combine short steps of the shear piezos into a longer move of the runner in either direction. See Fig 2.3.
Slew mode motion is divided into several different phases: Clamping piezos (group 2) unclamp, shear piezos (group 1) drive the runner forward while shear piezos (group 2) move backward, clamping piezos toggle, shear piezos (group 2) drive the runner forward while shear piezos (group 1) move backward. The available travel range therefore, can be scaled significantly with 10’s of millimeters as a normal range.
Fig 2.3 Slew mode operation (Image: PI) Slew mode motion begins and ends with zero control voltage on all piezo elements. This means that when powered down, the runner is held in place by the friction resulting from the high internal preload and can only be moved from its position by very high external forces.
In some applications, the discontinuities of the stepping motion described above can lead to undesirable oscillation of parts or assemblies. In such cases, it is possible for the slew mode controller to overlap the shear motion with the toggling of the clamping piezos, so that the piezos always clamp and unclamp the runner as it moves at a constant velocity. The operational compromise to obtain constant velocity slewing is lower force and step size compared to the full step slew mode.
2.3 Dynamic Park/Position Hold Mode
With the ability to slew and dither the Nexline actuator, another mode of operation can be realized. Upon a power off condition, the Nexline drive is programmed to remember it’s position, and by adjusting the voltage applied to the clamp and shear piezo actuators, it will hold it ’s exact position at the moment of the power off condition even as the PZT actuators discharge from their operating voltage to a zero volt condition.
This mode can also be implemented when the Nexline is in operation by commanding it to hold position while auto zeroing its bias voltage from programmed set points. Maintaining an average low bias voltage greatly extends the operational lifetimes of the Nexline actuator since PZT ceramic lifetime is proportional to the average operating bias voltage.
3. Application
This technology was originally developed for applications in the semi -conductor industry. There, heavy, extreme precision optics assemblies, weighing 10’s of kg, must be positioned vertically and aligned in multiple axes with nanometer resolution. The coarse positioning requirements are for quasistatic motion over several millimeters to compensate for the relatively large mechanical tolerances in the manufacturing of machine components and structures. The fine positioning requirements, however, entail motion over a few microns with subnanometer resolution and sufficient bandwidth to also compensate for vibrational disturbances.
A significant requirement is that once on target, the position must be held with nanometer accuracy without having to apply voltage to the piezo elements. Fig 3.2 shows a linear actuator which meets the requirements listed above.
Fig 3.1 N-111 miniature NEXLINE® linear actuators (Image: PI) Fig 3.2 N -216 high-force NEXLINE® linear actuator (Image: PI). See animation of the actuator here. (Image: PI) N-216 Operational Specifications:
- Up to 20 mm stroke
- 50 picometer resolution
- +/– 800 N ( 180 lb.) push/pull capability
- Actuator mass 1.2 Kg Actuator volume –340cc Stiffness – 45 N/micron
- Dynamic range over 2mm travel – >10,000,000
Also shown is a miniature version capable of 1.5 µm steps and forces to 50 N (see Fig 3.1).
In contrast to classical linear actuators, a number of components, such as leadscrew, gearbox, and bearings, can be dispensed with because the linear motion is generated directly. This makes it possible to realize very compact, low mass, high -load devices. Fig 3.3 shows a UHV-compatible hexapod made with fully nonmagnetic NEXLINE® actuators. Fig 3.4 shows a larger non-magnetic model for a complex alignment application involving superconducting magnets.
Fig 3.3 Compact, UHV-compatible, nonmagnetic hexapod based on miniature-NEXLINE® actuators. (Image: PI) Fig 3.4 High Force parallel kinematics piezo Hexapod w/ NEXLINE® actuators for use in high magnetic fields load capacity of >100 kg. (Image: PI) NEXLINE® actuators can be designed for a wide temperature range and are intrinsically vacuum compatible. Because of the temperature dependence of the piezo effect, the displacement of the individual piezo elements is reduced to about 30% at cryogenic temperatures. The maximum operating temperature of the PZT ceramics is about 120°C due to effects of thermal depoling.
4. Test Results
The performance of the actuators is proportional to the amount of shear piezos and the driving voltage applied to it. Fig 4.3 compares holding force vs. step size of several actuators. Fig 4.1 shows the smoothness of motion in full-step mode and nano-step mode. In slew mode, the maximum step size is about 6.5 µm. The maximum speed is proportional to the step frequency, which is generally limited by the controller used and by the amount of power available. Normal speeds are between a few hundred microns and a few millimeters per second. Reducing the amplitude of the voltages on the shear piezos results in smaller step sizes. The minimal reproducible step sizes are limited from 5nm to 10nm. This is determined by the surface microroughness of the contact areas, and by parasitic piezo movement due to the intrinsic non linearities in the piezo material.
Fig 4.1 PiezoWalk Linear Actuator, Nano stepping vs Full Step mode (Image: PI) Similarly, in dither mode, a reduction of the maximum control voltage swing will result in a decrease of the analog mode stroke. Fig 4.2 shows measured values for the motion of the runner of about 1 nm in response to 3 V square-wave signal. The resolution limit could not be determined, because the resolution of the capacitive sensor which was used was only about 50 pm.
Fig 4.2 Analog /Dither Mode: Train of 1 nm steps (top) and 50 pm steps (bottom) in open -loop. (Image: PI) As the force opposing the motion of the actuator is increased, the step size can be seen to decrease to zero. The reason is the elastic deformation of the piezo elements and the connecting structure, which leads to motion loss when the clamping piezos toggle. The maximum force which the actuator can withstand using maximum shear piezo control voltage amplitudes is called the blocking force and is between 300 and 800 N for off-the-shelf actuators.
Fig 4.3 Step vs. Force characteristics for several off-the-shelf PiezoWalk actuators (Mod. N-214, N-215 and N-216) (Image: PI) In the face of very high opposing forces — forces exceeding the normal preload times the friction coefficient — the runner would slide between the piezo actuators clamps (analogous to a slip clutch effect) and be driven to the mechanical hard stop. Those forces would need to be greater than 800 N for the N-216 model.
5. Conclusion
The development of the piezoceramic linear motors described here demonstrates that it is possible to combine long travel ranges, ultra -high resolution, and high force in a unified drive design. This drive additionally due to its high stiffness can move heavy loads dynamically. The drive is intrinsically self-locking and does not expend energy to hold a position. This development, as noted earlier, was undertaken for applications in the semiconductor industry, and multiple units in our lifetime test facility have demonstrated lifetimes of >108 slew and >109 dither mode cycles to date in continuing durability tests. The lifetime design goal of these actuators is 10 years in a vacuum environment. More testing is necessary for cryogenic applications and for mountain top observatory environments. From our experiences in extreme industrial applications, a simple and low cost dry air purge of a few cc’s per hour will ensure long actuator lifetime for ground based observatory environments.
The applications for ground and space astronomical telescopes with their associated instrumentation packages range from primary mirror segment positioning, active truss structures, and embedded coarse/fine position control in space constrained instrument packages. From a cost standpoint, NEXLINE actuators are higher in cost than conventional micropositioning drives. Yet when the requirement demands coarse/fine position control with nanometer level resolution, they are cost competitive, simpler to integrate, and occupy much less volume and mass than equivalent force hybrid mechanical actuation designs.
References :
1) K. Lorell et al; “Design and preliminary test of precision segment positioning actuator for the California Extremely Large Telescope”, Proceedings of the SPIE, Volume 4840, pp. 471-484 (2003).
2) United States Patent 6,800,984, “Piezo linear drive with a group of piezo actuator stacks as well as method for operating such a drive”, October 5, 2004.
3) Pitz, E. et al; “Five –axis secondary system for UKIRT”, Proc SPIE Conf. on Advanced Technology Optical Telescopes V”, ed. L.D. Barr, 2199, 516–522, 1994.
Blog Categories
- Aero-Space
- Air Bearing Stages, Components, Systems
- Astronomy
- Automation, Nano-Automation
- Beamline Instrumentation
- Bio-Medical
- Hexapods
- Imaging & Microscopy
- Laser Machining, Processing
- Linear Actuators
- Linear Motor, Positioning System
- Metrology
- Microscopy
- Motorized Precision Positioners
- Multi-Axis Motion
- Nanopositioning
- Photonics
- Piezo Actuators, Motors
- Piezo Mechanics
- Piezo Transducers / Sensors
- Precision Machining
- Software Tools
- UHV Positioning Stage
- Voice Coil Linear Actuator
- X-Ray Spectroscopy
USA / Canada
contact@pi-usa.usEAST
(508) 832-3456
MIDWEST
(508) 832-3456
WEST
(949) 679-9191 (LA Area & Mexico)
(408) 533-0973 (Silicon Valley/Bay Area) - Resources