- ProductsProductsPI is a worldwide leading supplier of solutions in the fields of motion and positioning. PI does not only develop and produce a broad range of positioning stages and actuators for linear, rotary and vertical motion or combinations of different axes. PI also adapts those solutions to customer-specific applications or supplies finished subsystems for motion and positioning.
- New ProductsNew Products
- Product FinderProduct FinderSelect 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 a time, for example, to find positioning stages designed for higher load capacity, too.
- Customized ProductsCustomized ProductsPI is fully at home where unconventional solutions are in demand. This is no longer limited to fields of research. Today, nanotechnology is also present in standardized industrial processes.
- Nanopositioning Piezo Flexure StagesNanopositioning Piezo Flexure StagesPI's piezo flexure stages combine sub-nanometer resolution and guiding precision with minimum crosstalk.
- Multi-Axis Piezo Flexure StagesMulti-Axis Piezo Flexure Stages
- PIFOC® Objective & PInano® Sample Scanners for MicroscopyPIFOC® Objective & PInano® Sample Scanners for Microscopy
- Linear Piezo Flexure StagesLinear Piezo Flexure Stages
- XY Piezo Flexure StagesXY Piezo Flexure Stages
- XYZ Piezo Flexure ScannersXYZ Piezo Flexure Scanners3-Axis Nanopositioning Scanners of Maximum Precision
- Piezo Flexure Tilting MirrorsPiezo Flexure Tilting Mirrors
- Multi-Axis Piezo Flexure Stages
- Miniature StagesMiniature StagesMiniaturized stages and manipulators are essential in mobile applications for measuring and medical devices, in industrial microassembly or use for research, e.g. in UHV and non-magnetic environments.
- Miniature Linear StagesMiniature Linear Stages
- Miniature Rotation StagesMiniature Rotation Stages
- Miniature HexapodsMiniature Hexapods
- Miniature Linear Stages
- Linear StagesLinear StagesPI offers a wide range of motorized linear stages to supply high-precision industrial markets like semiconductor and photonics, as well as high-end research. Vacuum versions are available for a large number of different models. Multi-axis compositions can be set up with adapter brackets or specialized vertical stages and compatible rotation stages.
- Stages with PIMag® Magnetic Direct-Drive Linear MotorStages with PIMag® Magnetic Direct-Drive Linear Motor
- Stages with Stepper, DC & Brushless DC (BLDC) MotorsStages with Stepper, DC & Brushless DC (BLDC) Motors
- Vertical Stages with Stepper, DC & Brushless DC (BLDC) MotorsVertical Stages with Stepper, DC & Brushless DC (BLDC) Motors
- Miniature Linear StagesMiniature Linear Stages
- Stages with PIMag® Magnetic Direct-Drive Linear Motor
- Linear ActuatorsLinear ActuatorsChoose from the widest range of technologies the optimum for your special demands: Set-and-forget applications benefit from the specific features of piezomotors that provide excellent long-term stability, also for vacuum or nonmagnetic environments. Stepper and DC motor solutions are well-established and reliable for both industrial and research use.
- PiezoMike for Long-Term StabilityPiezoMike for Long-Term Stability
- Linear Actuators with Stepper & DC Servo MotorsLinear Actuators with Stepper & DC Servo Motors
- PIMag® VC Voice Coil Actuators with High Dynamics & Force Control OptionPIMag® VC Voice Coil Actuators with High Dynamics & Force Control Option
- PiezoMove Lever ActuatorsPiezoMove Lever Actuators
- Nanopositioning Piezo ActuatorsNanopositioning Piezo Actuators
- PiezoWalk® Actuators with High Force & StabilityPiezoWalk® Actuators with High Force & Stability
- PIRest Active Piezo ShimsPIRest Active Piezo Shims
- PiezoMike for Long-Term Stability
- Rotation StagesRotation StagesPI offers stages with all kinds of motorization and guiding options: air-bearing, torque motor driven, motorized worm-gear coupled, tiny piezomotor stages and specialized goniometer stages with orthogonal tip-tilt mounting option.
- XY StagesXY StagesStability, precision and dynamics are crucial in the application fields of PI’s XY stages. They are the basis of high throughput rates and reliable operation. PI makes use of own developments in the fields of PIMag® magnetic linear motors and PIglide air bearings. Industrial production and quality control benefit from PI’s high-load XY stages and planar scanners.
- HexapodsHexapodsHexapods provide 6 degrees of freedom in the most compact package. In combination with absolute measuring sensors, software and motion controllers that make the most complicated motion profiles easy to command, PI hexapods answer industrial requirements.
- Engineered Subsystems for AutomationEngineered Subsystems for AutomationPrecision components, stable control and a great deal of experience in engineering are essential for high-precision complex motion and positioning solutions. PI is a supplier of technologically sophisticated drive components and high-precision positioners and also offers all levels of integration for engineered subsystems.
- Fast Multi-Channel Photonics AlignmentFast Multi-Channel Photonics Alignment SystemsPiezo scanners take care of fast, continuous scanning tasks, where durability, dynamics, and precision matter. The larger travel ranges are realized with XYZ combinations or 6-axis hexapods. Integrated routines make it possible to perform single-axis alignments up to complex, multi-axis fiber array positioning within the shortest possible time.
- Motion Control SoftwareMotion Control SoftwareAll digital controllers made by PI are accompanied by an extensive software package.
- User Programs and Their FunctionsUser Programs and Their Functions
- Software Tools for HexapodsSoftware Tools for Hexapods
- Third Party SupportThird Party Support
- Software Products for Special ApplicationsSoftware Products for Special Applications
- Controllers & DriversControllers & DriversThe decision for a motion controller depends on the specific application situation. Various criteria, such as limited installation space, the number of axes or the type of control, determine which controller is the right one. PI offers a broad spectrum of controls and regulation concepts.
- Nanopositioning Piezo ControllersNanopositioning Piezo Controllers
- Piezo Drivers for Open-Loop Operation of Piezo ActuatorsPiezo Drivers for Open-Loop Operation of Piezo Actuators
- Motion Controllers & Drivers for Linear, Torque, Stepper & DC Servo MotorsMotion Controllers & Drivers for Linear, Torque, Stepper & DC Servo Motors
- Controllers & Drivers for PiezomotorsControllers & Drivers for Piezomotors
- Controller Systems for Multiple Axes & Mixed Drive TypesController Systems for Multiple Axes & Mixed Drive Types
- Hexapod Motion ControllersHexapod Motion Controllers
- ACS Motion ControlACS Motion Control for Industrial Automation
- Nanopositioning Piezo Controllers
- Piezoelectric Transducers & ActuatorsPiezoelectric Transducers & ActuatorsPiezoelectric ultrasonic transducers are available in a wide range of shapes like disks, plates or tubes, and different performance levels. They can be adapted to application requirements by using different piezoceramic materials, electrodes, and assembling technology.
- Discs, Rods and CylindersPiezoceramic Discs, Rods & Cylinders
- Plates and BlocksPiezoceramic Plates & Blocks
- RingsPiezoceramic Rings
- TubesPiezoceramic Tubes
- Spheres and HemispheresPiezoceramic Spheres & Hemispheres
- Bending ElementsPiezoceramic Bending Elements
- Tube ActuatorsPiezo Tube Actuators
- PICMA® Piezo Linear ActuatorsPICMA® Piezo Linear Actuators
- PICMA® Piezo Bender ActuatorsPICMA® Piezo Bender Actuators
- PICA Piezoelectric Stack ActuatorsPICA Piezoelectric Stack Actuators
- PICA Shear ActuatorsPICA Shear Actuators
- DuraAct Patch TransducersDuraAct Patch Transducers
- Picoactuator® Piezoelectric CrystalPicoactuator® Piezoelectric Crystal
- Discs, Rods and Cylinders
- Air Bearings & StagesAir Bearings & StagesAir bearing stages are used where vibration-free motion is required, velocity needs to be highly constant, and optimum angular repeatability is requested.
- Sensors, Components & AccessoriesSensors, Components & Accessories
- 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).
- New Products
- OEMOEMCustomer- and application-specific product developments form the basis for success at PI. To this purpose, requirements have to be understood and a technological solution has to be found.
- ApplicationsApplications & MarketsPI positioning systems are employed where technology is pushed forward in industry and research. This is done, for example, in semiconductor manufacturing, in medical engineering, in biotechnology, in plant engineering, in surface metrology, or in astronomy.
- Hexapods Support Industrial RobotsHexapods Support Industrial Robots
- Scientific InstrumentationScientific InstrumentationThe term "scientific instrumentation" covers a variety of different applications, starting with microscopy via beamline processes through to the wide field of laboratory automation.
- Hexapod Systems for ALMAHexapod Systems for ALMA
- Double-Crystal MonochromatorDouble-Crystal Monochromator for an X-Ray Spectrometer
- Materials Research in High VacuumMaterials Research in High Vacuum
- Active Vibration Isolation with Piezo ActuatorsActive Vibration Isolation with Piezo Actuators
- Drive Technology for the ELTDrive Technology for the ELT
- Hexapod Systems for ALMA
- Semiconductor TechnologySemiconductor TechnologyLithographic processes are the reason why chips are getting smaller and smaller and why extremely fine structures can be realized on silicon wafers. Piezo drives have made these technical advances possible with their performance and reliability.
- MicroscopyMicroscopyImaging processes increase efficiency across a number of fields, ranging from medical engineering to pharmaceutical research and manufacturing of semiconductors.
- Confocal MicroscopyAdjustment of the Focal Planes in Confocal Microscopy
- Positioning Solutions for Total Internal Reflection Fluorescence Microscopy (TIRFM)Positioning Solutions for Total Internal Reflection Fluorescence Microscopy (TIRFM)
- High-Speed MicroscopyHigh-Speed Microscopy for Quality Control
- Atomic Force MicroscopyAFM Scanner for Atomic Force Microscopy
- White Light Interferometry3-D Surface Inspection With Piezo-Based Positioning Systems from PI
- Flamingo Lightsheet Fluorescence MicroscopyFlamingo Lightsheet Fluorescence Microscopy
- Confocal Microscopy
- Silicon PhotonicsSilicon PhotonicsSilicon photonics allows data rates into the Tbit/s range and is therefore suitable for computer-aided services that require the highest possible transmission speeds.
- Photonics PackagingAutomated Photonics Packaging
- Optical Fiber AlignmentSimultaneous Testing of Optical Components in Silicon Photonics
- Photonics Packaging
- Medical TechnologyMedical TechnologyProgress in pharmaceutical research, diagnostics, and therapy requires high-performance and precise position systems. In addition to high positioning precision, requirements for the drives often include compact dimensions, low energy consumption, speed, and high reliability.
- EndoscopyVariable Focusing and Sharp Focus for Endoscopic Applications
- OphthalmologyHigh-Precision Drives in Ophthalmic Surgery
- Magnetic Resonance ImagingNonsensitive Drives for Magnetic Resonance Tomography
- Optical Coherence TomographyPiezo Technology and Optical Coherence Tomography (OCT)
- PipettingPiezomotors for Pipetting and Nanodispensing
- Precision DosingDynamic Drives for Precision Dosing with Nanodispensers
- MicropumpsPiezoelectric Micropumps – Compact Design and High Performance
- Image StabilizationImage Stabilization and Microscanning with Piezo Scanners
- Adaptive Diaphragm PositioningAdaptive Diaphragm Positioning
- Positioning Solutions for Whole Genome SequencingPositioning Solutions for Whole Genome Sequencing
- Materials ResearchMaterials ResearchEfficiency has become an important buzzword these days. Materials research has paid a major contribution as the results have, for example, optimized processing methods. Methods such as X-rays and lasers or white light interferometry demand precise positioning of the specimens to be examined and of optics or beam control.
- Parallel Kinematics for Materials ResearchHigh-Load Parallel Kinematics for Materials Research
- Laser Beam ControlPiezo Drives for Laser Beam Control
- Parallel Kinematics for Materials Research
- Mechanical EngineeringMechanical EngineeringMechanical engineering and manufacturing technology require fast, reliable and energy-saving drive components. The spectrum ranges from piezo actuators to six-axis parallel kinematics which can communicate directly with CNC controls.
- Electrical Discharge MachiningPiezo Actuators Accelerate Electrical Discharge Machining
- Hexapods in Mechanical EngineeringHexapods in Mechanical Engineering
- Electrical Discharge Machining
- AutomationAutomationPiezo drives, magnetic direct drives, and hexapods are part and parcel of automation today. They operate precisely and reliably and have proven themselves under rugged conditions.
- Smarter Motion PositioningSmarter Motion Positioning
- Hexapods in MicroproductionHexapods in Microproduction
- Hexapods for Quality AssuranceHexapods for Quality Assurance
- Magnetic Direct DrivesMagnetic Direct Drives
- Motion Simulation with HexapodsMotion Simulation with Hexapods
- Flexibility in Dimensional MeasuringHexapod Systems in Automation
- Motion Compensation with HexapodsMotion Compensation with HexapodsDynamic hexapods with piezo drives: Best conditions for motion compensation.
- Fast Piezo Ultrasonic Drives Advance TechnologyFast Piezo Ultrasonic Drives Advance Technology
- Laser Material ProcessingLaser Material Processing
- Hexapods for Optical MetrologyHexapods Support Precise Measurement of Aspheres
- Smarter Motion Positioning
- Beamline InstrumentationBeamline InstrumentationScientific experiments pose their own challenges, and beamline X-ray experiments are even more special in themselves. However, the need for precision equipment is universal.
- Tomography EquipmentTomography Equipment
- Synchrotron Spectroscopy in VacuumSynchrotron Spectroscopy in Vacuum
- Beam PreparationBeam Preparation
- Sample Positioning for TomographySample Positioning for Tomography
- Accelerator TechnologyAccelerator Technology
- Tomography Equipment
- Additive ManufacturingAdditive ManufacturingDue to their high dynamics and pushing forces piezo actuators are highly suitable for the use in machines for additive manufacturing.
- Active AlignmentActive AlignmentThe assembly of complex optical systems like objective lenses for smartphone cameras or laser cavities requires more and more accuracy. Active alignment addresses the resulting needs and helps to reduce cycle times by two orders of magnitude and more.
- TechnologyKnow-How & TechnologyPI combines its long-term experience in micro and nanopositioning technology with in-depth knowledge in the fields of mechanics, electronics, sensor engineering, and software. Thus, PI is able to offer its customers the most advanced drive technologies and system solutions.
- Piezo TechnologyPiezo Technology
- Fundamentals of Piezo TechnologyFundamentals of Piezo TechnologyPhysical basics and explanations of piezo electricity and electromechanics.
- Properties of Piezo ActuatorsProperties of Piezo Actuators
- Piezoceramic MaterialsPiezoceramic MaterialsPI Ceramic offers a variety of different piezoelectric materials including lead-free materials.
- Manufacturing TechnologyManufacturing Technology
- PICMA® TechnologyPICMA® Technology
- Integrated Piezo ActuatorsIntegrated Piezo Actuators
- DuraAct Patch Transducer TechnologyDuraAct Patch Transducer Technology
- PIRest ActuatorsPIRest ActuatorsActive shims with long-term stability and nanometer resolution.
- Fundamentals of Piezo Technology
- Piezoelectric DrivesPiezoelectric DrivesDepending on the configuration and control, piezoceramic actuators can be used to create translational motions or as motors with a virtually unlimited travel range. The choice of drive depends on the requirements of the application.
- Piezo ActuatorsPiezo Actuators with and without Guiding
- PiezoWalk® Walking DrivesPiezoWalk® Walking Drives
- PILine® Ultrasonic PiezomotorsPILine® Ultrasonic Piezomotors
- Piezo Inertia DrivesPiezo Inertia Drives
- PiezoMike Linear ActuatorsPiezoMike Linear Actuators
- Comparison: Piezo Motors & Drive TechnologiesComparison: Piezo Motors & Drive Technologies
- Piezo Actuators
- Electromagnetic DrivesElectromagnetic DrivesRotating electric motors such as DC or stepper motors are used in connection with screw or worm drives. Stepper motor systems with high-resolution encoders can perform minimum incremental motions of 10 nm with high reliability and repeatability.
- Rotating Electric MotorsRotating Electric Motors from PI
- PIMag® Magnetic Direct DrivesPIMag® Magnetic Direct Drives
- PIMag® 6-D Magnetic LevitationPIMag® 6-D Magnetic Levitation at Six Levels of Freedom
- Hybrid ConceptPiezo & Motor Hybrid Concept
- Rotating Electric Motors
- Parallel KinematicsParallel KinematicsIn a parallel-kinematic, multi-axis system, all actuators act directly on a single moving platform. This means that all axes can be designed with identical dynamic properties, thus reducing the moved mass considerably. Hexapods are used for moving and precision positioning, aligning and displacing loads in all six degrees of freedom, i.e., three linear and three rotational axes.
- Parallel KinematicsPiezo Positioning Systems with Parallel KinematicsIn a parallel-kinematic, multi-axis system, all actuators act directly on a single moving platform.
- Multi-Axis PositionersMulti-Axis Positioners and Stewart Platforms
- Hexapod as Motion SimulatorHexapod as Motion SimulatorMotion simulators have higher motion dynamics requirements (shakers).
- Parallel Kinematics
- Sensor TechnologiesSensor TechnologiesThe linearity and repeatability achieved are not possible without highest-resolution measuring devices. Accuracies in the range of a few nanometers and below require a position measurement method that can also detect motion in this range.
- Capacitive SensorsCapacitance Nanosensors
- Incremental SensorsLinear Scale Encoders for Nanometrology & Nanopositioning
- PIOne Optical Nanometrology EncoderPIOne Optical Nanometrology Encoder
- Comparison: Position Sensor TechnologiesComparison: Nanopositioning Sensor Technologies
- Capacitive Sensors
- Controllers & SoftwareControllers & SoftwareFast settling or extremely smooth low speed motion, high positional stability, high resolution and high dynamics – the requirements placed on piezo systems vary greatly and need drivers and controllers with a high degree of flexibility.
- Digital & Analog InterfacesDigital & Analog Interfaces
- EtherCAT Connectivity of PI ProductsEtherCAT Connectivity of PI Products
- Control of Piezo ActuatorsPiezo Controllers & Drivers for Nanopositioning Systems
- Digital Motion ControllersDigital Motion Controllers
- Active AlignmentActive Alignment
- Digital & Analog Interfaces
- Guiding Systems & Force TransmissionGuiding Systems & Force TransmissionFlexure joints, mechanical guide components or magnetic bearings? Which kind of guiding system PI uses in its products depends on parameters such as travel range, required precision, load, lifetime, and ambient conditions.
- Classical Guiding SystemsComparison: Classical Guiding Systems and Force Transmission
- Flexure Guiding SystemsFlexure Guiding Systems for Nanopositioning & Piezo Actuators
- Magnetic BearingsMagnetic Levitation & Precision Bearings for NanopositioningMagnetic levitation allows excellent guiding accuracy in a plane, both linear and rotational.
- PIglide Air Bearing TechnologyPIglide Air Bearing TechnologyMulti-axis motion with nanometer precision and without friction.
- Classical Guiding Systems
- VacuumVacuum Compatible Linear & Rotary Stages, UHV PositionersCareful handling, adequate premises: PI does not only have the necessary equipment for the qualification of materials, components and final products, but also has many years of experience with regard to HV und UHV positioning systems.
- GlossaryPI Glossary for Technical TermsFind useful explanations of technical terms in the PI Glossary.
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- About PIAbout PIPI stands for technical excellence and continuous advance in precision positioning – driven by the passion for technology and its use in customer applications. The target of the PI Group is to develop this market and technological leadership even further and therefore secure a decisive competitive advantage for its customers.
- Technology CenterTechnology Center
- 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.
- MetrologyMetrologyPI qualifies its products with external measuring equipment. These are calibrated in part and traceable to a national standard. Using the PIOne incremental encoder and capacitive sensors, PI manufactures own metrology for inclusion in PI products.
- 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.
- Heavy Load HallHeavy Duty Hall for Positioning Systems Weighing Several TonsThe product range from a two-ton hexapod to a ten-gram nanopositioner requires that PI can both manufacture and qualify these systems. For this reason, PI operates a heavy duty hall at its location in Karlsruhe for the assembly and measurement of masses up to five tons.
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- The PI GroupThe PI GroupPI stands for technical excellence and continuous advance in precision positioning – driven by the passion for technology and its use in customer applications.
- About PI miCosPI miCos GmbH, GermanyAs a member of the PI Group, PI miCos makes a strong contribution in the field engineered systems and is the center of expertise for positioning systems with magnetic drives.
- About PI InnovationAbout PI InnovationTo be able to promote both the opportunity for innovative work and the implementation of the ideas at PI, the PI Innovation GmbH was founded as an "external staff unit" for innovation.
- About ACS Motion ControlAbout ACS Motion ControlACS Motion Control is an OEM-focused supplier of motion controller and drive solutions for high-tech systems in fields such as semiconductor manufacturing, laser processing, additive manufacturing, flat panel display manufacturing, electronic assembly, life sciences, and more. Headquartered in Israel, ACS has technical sales and support offices in the USA, Germany, China, and South Korea. ACS joined the PI Group in January 2017, when PI became a majority shareholder of ACS Motion Control.
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PI Ceramic offers various types of piezo actuators with different layer thicknesses. This results in nominal operating voltages of 60 V for PICMA® bender actuators and up to 1000 V for PICA actuators.
At operating frequencies well below the resonant frequency, a piezo actuator behaves like a capacitor. The actuator displacement is proportional to the stored electrical charge, as a first order estimate. The capacitance of the actuator depends on the area and thickness of the ceramic as well as the material properties. In the case of actuators that are constructed of several ceramic layers electrically connected in parallel, the capacitance also depends on the number of layers. In the actuators there are leakage current losses in the μA range or below due to the high internal resistance.
Accordingly, a PICMA® stack actuator with a layer thickness of 60 µm has an approx. 70 times higher capacitance than a PICA stack actuator of the same volume and a layer thickness of 500 µm. The electric power consumption P of both types is roughly the same due to the relationship P ~ C V2 since the operating voltage changes proportionally to the layer thickness.
When electrically charged, the amount of energy stored in a piezo actuator is approximately E = 0.5 CV2 . Every change in the charge (and therefore in displacement) is connected with a charge transport that requires the following current I:
Slow position changes only require a low current. To hold the position, it is only necessary to compensate for the very low leakage currents, even in the case of very high loads. The power consumption is correspondingly low. Even when suddenly disconnected from the electrical source, the charged actuator will not make a sudden move. The discharge and thus the return to zero position will happen continuously and very slowly.
Operation with Position Control
In closed-loop operation, the maximum safe operating frequency is also limited by the phase and amplitude response of the system. Rule of thumb: The higher the resonant frequency of the mechanical system, the higher the control bandwidth can be set. The sensor bandwidth and performance of the controller (digital or analog, filter and controller type, bandwidth) also limit the operating bandwidth of the positioning system.
Heat Generation in a Piezo Element in Dynamic Operation
Since piezo actuators behave like capacitive loads, their charge and discharge currents increase with the operating frequency. The thermal active power P generated in the actuator can be estimated as follows:
For actuator piezo ceramics under small-signal conditions, the loss factor is on the order of 0.01 to 0.02. This means that up to 2 % of the electrical power flowing through the actuator is converted into heat. In the case of large-signal conditions, this can increase to considerably higher values (fig. 3). Therefore, the maximum operating frequency also depends on the permissible operating temperature. At high frequencies and voltage amplitudes, cooling measures may be necessary. For these applications, PI Ceramic also offers piezo actuators with integrated temperature sensors to monitor the ceramic temperature.
P Power converted into heat [W] tan δ Dielectric loss factor (ratio of effective to reactive power) f Operating frequency [Hz] C Actuator capacitance [F] Vpp Piezo voltage (peak-to-peak) [V] Epp Electric field strength (peak-to-peak) [kV/mm]
Dielectric Loss Factors
Fig. 3 shows the dielectric loss factors tan δ for different materials and control modes at room temperature and with quasistatic control. The conversion between voltage and field strength for specific actuators is done with the layer thicknesses. The actual loss factor in the component depends on further factors such as the mechanical preload, the temperature, the control frequency, and the amount of passive material.
Continuous Dynamic Operation
To be able to operate a piezo actuator at the desired dynamics, the piezo amplifier must meet certain minimal requirements. To asses these requirements, the relationship between amplifier output current, operating voltage of the piezo actuator, and operating frequency has to be considered.
Both the average current and the peak current of the amplifier are relevant for driving a piezo actuator with a symmetrical triangular waveform. The maximum operating frequency of an amplifier can be estimated as follows:
A secondary constraint that applies here is that the amplifier must be capable of delivering at least Imax = 2 Ia for the charging time, i.e. for half the period. If this is not feasible, an appropriately lower maximum operating frequency should be selected. For amplifiers which cannot deliver a higher peak current or not for a sufficient period of time, the following equation should be used for calculation instead:
The effective or average current Ia of the amplifier specified in the data sheets is the crucial parameter for continuous operation with a sine wave. Under the defined ambient conditions, the average current values are guaranteed without a time limit.
For sinusoidal single pulses that are delivered for a short time only, the following equation can be used:
The above equation calculates the required peak current for a half-wave. The amplifier must be capable of delivering this peak current for at least half a period. For repeated single pulses, the time average of the peak currents must not exceed the permitted average current.
Signal Shape and Bandwidth
In addition to estimating the power of the piezo amplifier, assessing the small-signal bandwidth is important with all signal shapes that deviate from the sinusoidal shape.
The less the harmonics of the control signal are transferred, the more the resulting shape returns to the shape of the dominant wave, i.e. the sinusoidal shape. The bandwidth should therefore be at least ten-fold higher than the basic frequency in order to prevent signal bias resulting from the nontransferred harmonics.
In practice, the limit of usable frequency portions to which the mechanical piezo system can respond is the mechanical resonant frequency. For this reason, the electrical control signal does not need to include clearly higher frequency portions.
The fastest displacement of a piezo actuator can occur in 1/3 of the period of its resonant frequency. Response times in the microsecond range and accelerations of more than 10,000 g are feasible, but require particularly high peak currents from the piezo amplifier. This makes fast switching applications such as injection valves, hydraulic valves, switching relays, optical switches, and adaptive optics possible.
For charging processes with constant current, the minimal rise time in pulse-mode operation can be determined using the following equation:
As before, the small-signal bandwidth of the amplifier is crucial. The rise time of the amplifier must be clearly shorter than the piezo response time in order not to have the amplifier limit the displacement. In practice, as a rule-of-thumb, the bandwidth of the amplifier should be two- to three-fold larger than the resonance frequency.
Advantages and Disadvantages of Position Control in Switching Applications
A closed-loop controller always operates in the linear control range of voltages and currents. Since the peak current is limited in time and is therefore nonlinear, it cannot be used for a stable selection of control parameters. As a result, position control limits the bandwidth and does not allow for pulse-mode operation as described.
In switching applications, it may not be possible to attain the necessary positional stability and linearity with position control. Linearization can be attained, e.g., by means of charge-controlled amplifiers or by numerical correction methods.