Miniature Positioning Stages / Linear & Rotary Stages

Ultrasonic motor direct drives are based on the piezo effect. A compact piezoceramic actuator is driven at inaudible frequencies of 100’s of kHz (hence the ultrasonic designation), and with each cycle transfers nanoscopic motion to a linear or rotary ceramic surface bonded to a linear runner or rotary platform. Ultrasonic motors provide very fast start/stop behavior, smooth motion with a very wide dynamic range from microns/second to 100’s of millimeters/second.

Ultrasonic motors are self-clamping at rest, provide excellent long-term stability, there is no servo dither, or energy consumption once a position has been reached. While high velocities can be achieved with ultrasonic motors, when continuous scanning is required, magnetic linear motors and voice-coil drives, such as in the V-522 miniature stage, are recommended. Ultrasonic drives permit the design of very compact positioners; the motor design is intrinsically non-magnetic and vacuum compatible.

These ultrasonic motor driven rotation stages provide high velocity to 720°/second and compact dimensions. They are equipped with optical, direct metrology encoders, and due to the self-clamping motor design, boast excellent position stability. The U-628 is the largest example featuring a table diameter of just under 2”. With Ø30mm and Ø20mm, respectively, the U-624 and U-622 are even more compact versions of the U-628 rotary stage.

Stick-slip piezo motors (inertia motors) permit the design of the smallest class of precision motorized positioners. The direct drive motors are only a few millimeters in size, there are no gears, or other conventional power transmission components involved that add size, complexity, play or backlash.

Inertia piezo motors make use of the difference in the static and dynamic friction coefficients between two surfaces; their controllers provide a quasi sawtooth output voltage, with a slow expansion phase and a fast contraction phase. In the expansion phase, the piezo actuator moves the slider; in the contraction phase, its inertia prevents the slider from following the quick motion of the actuator, and it remains at its position.

Piezo inertia motors can be operated in open loop, but for high accuracy and repeatability, a position encoder is integrated in the stage. Vacuum compatible and non-magnetic versions are also offered. The PIShift piezo inertia drive is very quiet, due to its high operating frequency of 20 kHz. 

PiezoWalk is a more powerful and complex drive than stick-slip and ultrasonic motors. PiezoWalk motors combine long travel with high stiffness and force, providing virtually unlimited travel ranges. PI’s NEXACT® motor technology integrates these advantages into a small package. Piezo-class resolution, millisecond responsiveness with low operating voltages, and a self-clamping design are other features.

The motors offer multiple operating modes including a high-dynamics, short-range dither mode with 100’s of Hertz bandwidth and picometer resolution, and several long distance modes optimized for highest force, highest speed, and constant velocity.

Piezo flexure-guided positioning stages provide several advantages over classical motorized positioning systems with mechanical bearings. They are completely free of backlash and friction and can position and settle in milliseconds or even microseconds. Driven by a piezo ceramic (with optional flexure motion amplifier), the response time is based on the sound propagation in the ceramics.

Piezo flexure stages are used when extremely smooth motion, fast response, high force or continuous scanning is required, with travel ranges typically below 1 millimeter. PI flexure stages are driven with PI’s exclusive PICMA piezo elements that have been life tested for 100 billion cycles and were selected by NASA /JPL for the Mars mission due to their extremely high performance and reliability.

A hexapod is based on a 6-axis (XYZ, Pitch, Roll, Yaw) actuator system arranged between a top and bottom platform.  Hexapods are also referred to as Gough-Stewart platforms and offer 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.

PI's miniature hexapods are available with different configurations: standard, high-speed, vacuum, and high resolution.

In addition to hexapods, PI offers a second class of planar 6-axis parallel manipulators. These piezo motor driven units are even smaller and fit inside the palm of a hand.