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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
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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.
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- 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.
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- 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.
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- 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
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- 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.
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- 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.
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- 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.
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- 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.
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- 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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- 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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Stepper Motor Basics
Many processes in production, automation, and research rely on precisely moving, adjusting and aligning tools, optics, and components.
Precision positioning equipment, based on a rotating electric motor and some kind of screw drive or worm gear drive to transfer and convert the output at the motor shaft into motion at the positioning actuator or stage, is widespread in the industrial sector. Stepper motors are considered robust, cost efficient, and provide a long service life. They provide high torque even at low speed, and are easy to control.
Basic operating principle of a stepper motor (Image: Wikipedia) Stepper motors take discrete positions of constant distance. The most common stepper motors are two phase / four phase motors with 200 to 500 full steps per revolution. Advanced controllers can interpolate thousands of microsteps between each full step to achieve higher resolution. A controller commands a position by issuing a number of electric pulses. Position feedback is not required, but can help to improve performance. If no position feedback is used, parameters such as maximum acceleration have to be considered to avoid stalling the motor during acceleration. A mechanical damper on the motor shaft, which also works as a handwheel, supports smooth running and helps to achieve better dynamics. A combination of suitable linear measuring systems and high-resolution controllers increases the positioning repeatability.
Stepper motors can hold a position very stable, without jitter, but current must be applied continually unless brake mechanisms or self-locking gearboxes / screw drives are used. Stepper motors can heat up during (continuous) operation and this must be taken into account when designing a system.
Several stepper motor driven precision positioning stages from PI miCos: (left to right) L-511 linear stage (former PRS-110), MCS Planar XY stage, L-310 Z-axis stage (former ES-100), L-611 rotation stage (former PRS-110) (Image: PI miCos) Precision Positioning, Down to the Nanometer Range
A linear positioning stage equipped with a 2mm lead screw, driven by a stepper motor with 200 full steps (1.8° per step) provides linear motion in 10µm increments for each motor step. This is hardly considered precision motion in the 21st century and microstep controllers can improve the performance considerably. A simple microstepper with 16 microsteps already brings this number down into the sub-micron range at 0.625µm and 39 nanometers are calculated for a 256 interpolation factor. Bear in mind, low friction mechanics are required to achieve this calculated resolution in the real world.
Higher interpolation means smoother motion and better resolution and economical controllers such as the C-663.12 Mercury Step already provide 2048 microsteps. Advanced controllers, such as the SMC Hydra, provide virtually continuous, step-less behavior similar to a brushless motor. In addition to higher position resolution, dynamic velocity, and acceleration range, vibrations that are present in full step mode are now virtually absent.
Coupled to a high-precision, low friction mechanical positioning stage, stepper motors can achieve linear resolution in the nanometer range, even when operating without the help of position feedback such as a linear encoder.
Shown above, repeated 25-nm steps measured with a laser interferometer: performance of an L-509 (below), entry level precision positioning stage operated in open loop (no position feedback. The stage is equipped with a 2-phase stepper motor (200 full steps) and 1mm ball screw and driven by an SMC Hydra controller with 3000 microsteps. (Image: PI miCos) Position Feedback Improves Repeatability and Linearity
Position feedback, in the form of a direct-measuring linear encoder can further improve the accuracy and repeatability. Drive train errors caused by backlash and friction in the drive screw, gear-box or the guiding system are now seen by the controller and can be compensated for.
Shown above, closed-loop performance: 10-nm steps of an L-511 linear stage (below) with 2-phase stepper motor, with linear encoder. Even steps as small as 10-nm steps can still be resolved, the repeatability for a motor/screw-drive system is remarkable. (Image: PI miCos) Stability and Resolution of Closed-Loop Steppers Compared to Servo Motors
Position-controlled stepper motor axes are known for excellent in position stability. Traditional classical (DC) servo systems exhibit typical controller oscillation up to a few encoder counts. For low-friction, low-damping situations, this can lead to instability if the servo parameters are not set carefully.
A typical servo system feeds off errors, i.e., it needs to see an error before it reacts. These effects do not occur with a stepper motor, because it does not need the servo to maintain a stable position. Actually, when a current is applied to the stepper motor, it creates a moment that keeps it in place, while a servo motor wants to move the moment a current is applied. Stepper motor controllers provide an intrinsic velocity feedforward, which allows them to run at extremely constant velocity, even at very low speeds, without the help of an additional tachometer.
However, if the microstep resolution of the controller is too low, a disparity between the motor and the encoder resolution can lead to a quantization of the achievable positions. In case of the SMC controller with 3000 microsteps, the angular motor positions are virtually continuous – for a 1mm drive screw, the calculated resolution is 1.6 nanometers- typically below the achievable resolution of a positioning stage with mechanical bearings.
Shown above, incremental linear encoders are often used for position feedback and position information is usually transmitted as analog sine-cosine signals with an output range of 1 Vpp, then digitized and interpolated in the controller down to the nanometer range and below. The measurement above shows the performance of a reference class linear encoder (model PIOne, at 400 kHz bandwidth and 18-bit resolution): 16pm RMS and 100pm peak-to-peak are feasible. (Image: PI miCos) Step-and-Settle Behavior
Good step-and-settle behavior is important for high throughput and time critical processes. In addition to the mechanical design, the control algorithms have a strong influence on the performance. SMC controllers suppress high frequencies and still allow dynamic positioning with minimal overshoot, eliminating oscillations and side effects for the overall system stability.
The mass of the payload, the resulting moments, and the orientation of the motion axis must be taken into account when optimizing the control parameters. Further measures are not necessary; the system is stable, and optimized dynamically.
1-mm steps, executed by an L-511 with position control (velocity 15 mm/s; acceleration 200 mm/s2) (Image: PI miCos) Zoomed view shows overshoot of less than 10 µm. The insert shows that only one single oscillation occurs. The target position is reached within a few tenths of a second within a window of less than 20 nm. (Image: PI miCos) Constant Velocity at Low Speed Motion
Velocity is a decisive parameter for selecting a positioning system. Often, the highest speed is what counts, but, some applications require particularly slow constant motion. In some scientific applications, velocities can range from a few 100µm/sec to considerably less than 100nm/sec, corresponding to a feed of a few millimeters per day. To achieve very uniform motion, a positioning system with a resolution around one nanometer is recommended.
Shown above, this detailed view shows a big difference. The 16 microstep controller cannot resolve below 0.6 microns and each step is clearly visible at this resolution. The 3000 microstep controller performs smooth motion with almost perfect straightness. Tests in closed loop operation have shown additional improvements. (Image: PI miCos)
Shown below, 16 microstep performance in constant velocity mode (open loop): position deviation compared to ideal target position based on constant velocity. Note, the peak-peak deviation is only 1.5µm. The controller’s limited resolution of 0.6µm is largely responsible for behavior shown below. (Image: PI miCos)
Show above, position deviation compared to ideal target position based on constant velocity with 3000 microstep controller (constant velocity mode, closed-loop): the high resolution microstep controller shows significantly improved performance compared to the 16 microstep behavior. (Image: PI miCos)
Shown below, FFT: Frequency spectrum of the position deviation of the 3000 microstep controller (Image: PI miCos)
Dynamic Position Correction (Error Mapping)
Error mapping (dynamic position correction) is a common technique to improve the overall accuracy of linear and rotary positioning stages. Improvements up 1000% are feasible.
For this purpose, the deviation from the target position at a predefined step size is measured with a reference measuring system. The measured deviations are stored in a table inside the controller. During operation, the controller dynamically applies the information gathered from the reference system and applies a correction factor for each target position correcting the motion profile on the fly.
Measurement Set-Up, Ambient Conditions, Test Equipment
All measurements were performed under standard lab conditions, temperature 22°C ±1°C, humidity 43% ±3%. A vibration isolated table was used, but no additional isolation from thermal, acoustic or other external influences. Ambient conditions can have a strong influence on the achievable precision. For a typical positioning stage made of aluminum, a 0.01°C fluctuation of the ambient temperature is equivalent to a position change of 10nm. A stable environment is basic requirement for precision motion in the sub-micrometer range. The user of special material pairings can help, too.
The following measurement equipment was used:
(left) Linear measuring device: Renishaw XL-80 interferometer, with reference mirror 25 mm above the motion platform. (Image: Renishaw) (right) Rotational measuring device: Heidenhain RON-905 (Image: Heidenhain) Shown above, the position noise of an L-511 linear stage, with energized motor, driven by the SMC Hydra controller in closed-loop mode. The noise level is at approximately 3 nm (peak-peak, 10 kHz sample frequency, unfiltered) which can be attributed to the interferometer and environment during the time of the measurements. (Image: PI miCos)
Positioning Systems and Motion Controllers
The following standard linear and rotation positioning systems and controllers were used for the above tests.
- L-511 Linear Stage (formerly LS-110) open and closed-loop versions
- L-509 (formerly PLS-85) open and closed-loop versions
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(left) SMC Hydra controller, 3000 microsteps per full step with integrated DeltaStar Eco encoder interface module (1 Vpp sin/cos input). (Image: PI miCos) (right) C-663.12 Mercury Step, compact economical controller with 2,048 microsteps. (Image: PI miCos) Blog Categories
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