Hybrid Nanopositioning Controller

Motion Controller for Piezo & Servo Motors Combined

  • Two channels
  • 10kHz Sampling Rate
  • 24-Bit Piezo Motion Resolution (<1 picometer)
  • High-Resolution Incremental Sensor with Serial Interface
  • Real-Time Operating System
  • Interfaces: VGA, Keyboard, Mouse, RS-232, TCP/IP Ethernet

One Motion Controller for Hybrid Linear Stages
In PI hybrid linear stages, such as the motor-leadscrew and piezo actuator are fully integrated to form one motion system. The motor and piezo act together at all times.

The result is far more than a coarse-adjust/fine-adjust system: effects like startup stick/slip and backlash can be completely compensated and a motion profile with high constancy of velocity can be followed. Because of the high piezo stiffness, setting to a few nanometers only takes a few milliseconds, significantly faster than with conventional, higher-inertia, linear-motor-driven stages. Furthermore minimal increments in the range of the sensor resolution can be reliably executed.

To allow high velocities beyond 100 mm/sec and nanometer-range incremental resolution, position information must be transmitted and processed very rapidly and a complex control algorithm is required. PI’s C-702 is a motion controller providing PWM signal generators, piezo amplifiers and control algorithms specially tailored for hybrid systems.

Advantages of the New Hybrid Motion Drives

  • Active Compensation of Stick/Slip During Startup and Settling
  • Active Backlash Compensation
  • Excellent Velocity Control
  • Millisecond Settling to Nanometer Accuracy
  • Reliable Execution of Minimal Increments
  • High Drive and Holding Forces with Minimal Power

C-702 Motion Controller—Key to Hybrid Technology
The optimized interaction between the piezoelectric and motorized drive components to make them a single motion unit requires a high-speed sensor as well as powerful control algorithms. The digital, 2-channel, C-702 controller, based on modern CPU technology with a real time operating system, has been designed for this task. It is able to read the position signals with virtually no delay and process the data immediately. The integrated piezo amplifiers use a high-resolution 24-bit DAC to fully support the high position resolution of the piezo actuators. The new ultra-fast SSI interface for the optical linear encoder supports stage velocities of 600 mm/s at a resolution of 1 nanometer. With custom firmware, one of the sensor interfaces can be reprogrammed for use as a high-speed command interface capable of processing commands at the servo rate.

Absolute Accuracy 
The servo-control loops for both the motorized and the piezo drive use the same position sensor. The result is a motion system with hundreds of millimeters travel but with the precision of a piezo-based nanopositioner. The resolution and the positioning accuracy depend on the choice of the feedback sensor. PI hybrid systems currently use optical linear encoders with a resolution of 2 nanometers. Depending on the stage, a minimum incremental motion or a repeatability of 4 nm can be achieved over the entire travel range.

Typical Applications 
Surface Inspection, Microscopy, Laser Technology, Interferometry Metrology

 More Information on Hybrid Nanopositioning


Motion Controller Overview

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