- 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.
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- 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
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- 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.
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- 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.
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- 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
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- 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.
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- 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).
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- 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.
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- 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.
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In free space optical communication (FSO), large amounts of data are “beamed” between two points – on earth, on aircraft or between satellites in space. Fast steering mirrors (FSM) are one means to compensate for disturbances that could keep the laser beam from hitting its target receiver precisely. Piezo flexure mechanisms such as tip/tilt platforms provide fast response, high resolution, and stability - ideal prerequisites for applications such as scanning, tracking, image stabilization, and free space optical communication. Since piezo motion is based on a solid state effects, piezo-driven systems and scanners can offer greater acceleration and dynamic bandwidth than voice coil or galvanometer scanners. When operated in closed-loop, piezo tip/tilt systems provided by PI can also achieve exceptional stability over long periods of time, for quasistatic positioning of optics with high demands on "pointing stability".
For highest guiding performance and life-time, flexure guides are used (Fig 1). Resolution into the nanoradian range are feasible along with high angular stability. Optical deflection angles of up to 70 mrad can be achieved with very short settling time (milliseconds to microseconds).
PI piezo tip/tilt systems are offered in single- and multi-axis versions. In addition, differential piezo tip/tilt systems are equipped with two piezo actuators per axis.
The design of a simple single axis system with a flexure guided tilt platform and one piezo actuator is shown in Fig. 1. The flexure forms the center of rotation (pivot point) and at the same time, preloads the piezo actuator. Simple design, low costs, and minimum space requirements are advantages of this version. A differential piezo drive is recommended for applications that require high angular stability over a wide temperature range.
Actuators are operated electrically in a bridge circuit supplied with a fixed voltage and controlled by a variable voltage (see Fig 2 for schematic diagram of 2-axis tip/tilt platform.
The differential design allows the highest angular stability over a wide temperature range because the changes in temperature only affect one linear offset shift of the platform. Strain gauge sensors applied to the flexures or PZT actuators allow operation in closed-loop mode providing high linearity and excellent repeatability.
Fig. 1a Single flexure, single piezo actuator (PZT) tilt mirror platform design. Advantages are the straightforward construction, compact dimensions and low costs. If thermal angular stability over a large temperature range is a critical issue, a differential piezo actuator drive system is recommended (image: PI) Fig 2. Schematic diagram of of 2-axis tip/tilt platform with differential drive (quattro pod). The actuators are physically arranged in two opposing pairs spaced at 90° intervals Multi-axis piezo tip/tilt systems are designed as parallel-kinematic systems (tripods or quattro pod) with all actuators acting on one platform. This design has great advantages compared stacked single axis systems. The motion platform is displaced only around one fixed center of rotation. Parallel-kinematic designs are well known from 6-DOF (degree of freedom) systems such as hexapods. Fig. 3b shows a high-speed, 6-axis motion system based on voice coil actuators.
A parallel-kinematic design reduces the moved mass (inertia) resulting in higher dynamics, compared to a mechanically stacked tip/tilt platform. The single pivot-point design also provides higher linearity and prevents the drawback of polarization rotation, which is common with conventional systems based on two individual single-axis galvo scanners operated sequentially.
For 3-axis applications a (Z-tip-tilt) a tripod design is used, as illustrated in Fig. 3a.
The multi-axis design in "tripod" form is driven by three piezo actuators arranged with gaps of 120° in between. The advantage of driving with three independent piezo actuators means that, in addition to tilting, the platform is also capable of liner motion which means, for example, that the controller can make use of optical phase differences (phase shift).
Fig 3b. A flexure-based, 6-axis parallel-kinematics motion platform. The struts of this high dynamics hexapod are driven by voice-coil motors. Systems like these 6-axis platforms are often used for camera shake and image stabilization algorithm testing.
PI piezo flexure mechanisms are tested and calibrated using interferometers or autocollimators. Standard tuning provides the best overall performance in a wide range of applications. Custom system tuning can be tailored to match particular applications such as fastest settling with minimum overshoot and highest linearity for long travel ranges. A performance test sheet provides details on specifications such as linearity etc.
Some tip/tilt platforms come with a factory-installed mirror. For user-installed mirrors, guidelines in the manual should be followed. In any case, excessive force needs to be avoided; after all, these are precision mechanisms with nano-scale positioning capabilities. The mass of the mirror or optic mounted on the platform has an influence on the dynamic performance of the system. The greater the mass of the mirror or beam splitter mounted, the lower the resonant frequency and step & settle performance.
A centering tool (Fig. 5) and a 3-point template are recommended for handling mirrors and applying the adhesive. The template and the centering tool can be found here.
The template indicates the position the adhesive on the tip/tilt platform and restricts the quantity of the adhesive to be applied to avoid leakage inside the actuator housing. For best results, epoxy resin-based two-component adhesives with a hardening temperature of approx. 20 °C are recommended. Alternatively, PI can also mount the mirror as part of the order.
Fig. 5 S-335.2SH piezo tip/tilt system with 3-D printed centering tool (blue) for applying a 1-inch mirror (image: PI)
If the mirror has to be removed, PI recommends heating the mirror carefully with a hair dryer or hot-air gun to soften the adhesive. It should then be possible to remove the mirror easily.
Since the dynamic properties of the piezo tip/tilt system are related to the moment of inertia, changes to the load (inertia) may require an update of the servo control parameters in the piezo controller to guarantee the highest performance.
Analog and digital servo controllers are available for operation.
Digital servo controllers (Fig. 6) are recommended for most applications, especially when demands on the system performance vary, because retuning can be performed easily by software.
While analog servo controllers can provide cost benefits, they lack flexibility for remote tuning and the advantage of advanced algorithms with higher order error correction.
Fig. 6 E-727 digital servo controller / driver for multi-axis piezo flexure mechanisms. The latest version comes with an EtherCat interface for enhanced connectivity in industrial applications (Image: PI)
More background information on piezo servo controllers is available in this article: Advances in Piezo Nanopositioning Controllers – Digital vs. Analog
A graphic user program called PIMikroMove is available to update servo control parameters by simply pressing a button. An ID chip in the connector of the piezo tip/tilt system stores all factory calibration and tuning parameters and allows for a quick swap of controller and piezo mechanics in the field.
The PIMikroMove package also offers diagnostics tools and many functions and options for displaying important system data. PI also provides LabVIEW drivers and the entire control and measuring logic as a Dynamic Link Library (DLL) for easy integration into complex OEM systems.
5.2 PIMikroMove: Easy Configuration and Startup
PIMikroMove is an integral part of the extensive software package that is included in the scope of delivery of every digital PI controller. The software ensures easy and intuitive system startup.
In addition to position control commands, specification of step-size, and acceleration parameters, etc., a macro programming language can tie a string of single commences into continuous motion sequences.
Complex trajectories, should be programmed in the various high-level languages such as C, C++, C#, Python, LabVIEW as well as MATLAB and Simulink that are supported by PI.
Tuning and system analysis tools are also integrated to optimize and test each individual function of the system.
A data recorder can capture motion data during a move which can be displaced by a graphing tool for easy analysis.
MikroMove User software – Used in photonics alignment application shown.
Piezo ceramic material expands quasi-proportional to the applied drive voltage. When run in open-loop (voltage control) mode, nonlinearity and hysteresis effects on the order of 10-15% are to be expected (Fig 7). Closed-loop piezo mechanisms are equipped with position sensors and are operated by a closed-loop servo controller that eliminates the nonlinearity and hysteresis effects, providing for higher accuracy and repeatability down to the nanoradian range.
6.2 Resonant Frequency
The dynamic properties of a piezo mechanism are related to its resonant frequency. The resonant frequency increases when the mechanical stiffness increases and drops when and moving mass is increased.
A rule of thumb is that the higher the resonant frequency, the higher the maximum operating frequency that can be achieved (the maximum operating frequency is usually significantly lower than the resonant frequency). In closed-loop operation, the maximum safe operating frequency is also limited by the phase margins of the system and a higher mechanical resonant frequency allows for a higher control bandwidth.
Resonant frequency of an ideal spring-mass system:
The above equation shows that in order to double the resonant frequency of a spring-mass system, either the stiffness must be increased by a factor of 4 or the effective mass reduced to 25 % of its original value.
For soft systems with heavy loads, dynamic operation is not possible.
Fig. 8a shows the resonant frequency of an S-335 piezo steering mirror as a function of the mirror size.
Fast response is a beneficial characteristic of piezo mechanisms. A rapid change of the operating voltage causes a rapid change in the expansion (displacement) of the piezo ceramic actuator and therefore a change in the tip/tilt platform's position.
If the drive voltage increases rapidly, a piezo actuator can reach its nominal displacement in approx. 1/3 of the resonant frequency period (given the driver can provide enough current). In an open-loop system (or inappropriately tuned closed-loop system), such a rapid voltage change can induce overshoot and oscillations. (Fig. 8b)
The influence of the P-term value on overshoot and step & settle performance of an S-335.2SH piezo tip/tilt system is shown in Fig 9.
Fig. 10 depicts the influence of load / inertia (mirror size) on the settling performance.
The positioning repeatability depends on the displacement and the type of sensor employed in the system. Film or piezoresistive strain gauge sensors (SGS) are most often used in compact piezo mechanisms for their small size and low cost – they can be applied directly to the piezo actuators. With these analog sensors, the absolute repeatability improves with shorter displacement ranges. Residual errors result from the inferred position measurement and the strain gauge sensor technology itself. It would be beneficial to measure the platform angle directly, but for most applications it is either not possible (size) or the advantages do not warrant the additional expense.
Repeatability performance can be measured with auto collimators or laser interferometers. Fig. 11 shows the typical S-335 repeatability performance graph based on 100 measurements (the deviation between the target and actual position is graphed as "position error") and the distribution in a histogram shown on the right.
6.4 Heat Generation During Continuous Operation
During long-term operation, heat generation can limit by the maximum operating frequency of the system. Because piezo actuators behave electrically similar to capacitive loads, their charge and discharge currents increase with the operating frequency. The drive voltage (equivalent to the angular displacement) has a quadratic influence on the power requirements and thermal loss. For more information on high frequency operation of piezo actuators, read Advances in Piezo Actuators for High Frequency, High Duty Cycle Industrial Applications
Due to the nonlinear, hysteretic properties of the piezo material, 8 to 12% of the electrical drive power put into the piezo actuators is lost as thermal energy. Therefore, cooling measures may be necessary at higher frequencies and amplitudes.
Fig. 12 shows the temperature rise over time of an S-331.2SL piezo tip/tilt system operated at 2000Hz (sine) with 100Vpp drive voltage (~70% max travel). The change of temperature was measured at the piezo ceramics.
In a closed-loop piezo positioning system the position creep known from open-loop piezo actuators is compensated by use of a position sensor and servo controller. Nevertheless, minimal position deviations can still be caused by temperature fluctuations. The use of differential piezo drives and sensors is recommended for optimum results.
6.6 Lifetime
Flexure guided piezo positioning systems provide very high reliability because of their frictionless, maintenance and wear-free characteristics of all included components. The lifetime of a well-designed piezo ceramic actuator is not subject to traditional mechanical wear of a standard actuator. Tests run by NASA/JPL have shown that PICMA® piezo actuators (the same types as used in all PI tip/tilt systems and piezo flexure nanopositioning stages) show no failures after 100 billion cycles. Because of the high performance, these multilayer actuators were selected for the Mars mission and integrated into an instrument on the Mars Rovers science lab.
Many years of careful design, testing and continuous improvements have lead to the extreme reliability of these monolithic piezo actuators. For example, the PICMA® piezo stack is covered entirely by a ceramic insulation layer that protects the actuators from humidity and failure resulting from increased leakage current, extending the lifetime considerably.
Micro-slots (Fig 13a) embedded in piezo stacks effectively prevent an excessive increase of mechanical tensile stress in the passive regions of the ceramics as well as uncontrolled expansion of micro cracks that would lead to dielectric breakdowns causing damage to the actuator.
The meander-shaped design of the external contact strips ensures stable electrical contact to all inner electrodes, even under extreme dynamic loads with high currents (Fig. 13b).
7 OEM Engineering and Custom Solutions
PI has a long and successful history of working with customers on OEM solutions. Often it starts with a COTS (Commercial Off-The-Shelf) product. Small modifications can be achieved in a small time frame. Based on the large experience, design tools and standard modules available, our engineering teams can design custom solutions quickly.
PI USA has been registered with the US Department of State since 2005 and has an ITAR TCP in place to fulfill the needs of customers with Export Controlled Applications. PI works with US customers on COTS and customer piezo / nanopositioning requirements under the ITAR TCP.
Extensive testing and production equipment allow PI to react quickly to the development and production requirements of highly complex custom products and assemblies. All development procedures and production processes, from the initial idea to the final product, are controlled via a comprehensive management system.
All motion and positioning systems manufactured by PI undergo endurance testing with various load, operating and control conditions.
Fig. 14 FEA simulation of tilt platform (image: PI) FEA (finite element analysis) tools are employed to optimize the performance and minimize material stress and potential for failure, ensuring high precision, and functionality before the first prototype is built.
Flexures, for example, which serve as guiding and preloading elements have a large optimization potential and our engineers are experts when it comes to flexure design. FEA helps find the best compromise between mass, size and stiffness, enhancing stability and reducing undesired creep effects.
Modal analysis during FEA optimization helps to reveal system resonances and other dynamic characteristics.
9 System Level Simulation
To gain insights into the overall system performance, parameters such as resonant frequency, damping, the electrical capacitance of the piezo actuators, servo control bandwidth etc. are used for a holistic simulation model. Based on these tools and extensive design experience, feasibility of customer requirements along with an early risk analysis can be performed quickly.
Author: Armin Karle is design engineer in the Piezo Systems R&D group at PI’s Headquarters.
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