A Compact Hall-Effect-Sensing 6-DOF Precision Positioner

Abstract

This paper presents the design, control, and implementation of a compact high-precision multidimensional positioner. A 1.52-kg single levitated moving part, named as the platen, generates all six-axis fine and coarse motions, resulting in a reliable and effective positioning system. Three laser distance sensors are used to measure its vertical translational motion and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -axis rotational motion. Three two-axis Hall-effect sensors are used to determine its lateral motions and rotational motion about the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -axis by measuring the magnetic flux density generated by a magnet matrix. Real-time control is implemented on a Linux-based operating system, Real-Time Application Interface (RTAI) with COntrol and MEasurement Device Interface (Comedi) and Comedi libraries. A maximum travel of 220 mm in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -direction and 200 mm in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction, and a rotation angle of 18.6° about the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -axis were achieved experimentally. A maximum velocity of 0.3 m/s with an acceleration of 3.6 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was obtained in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction. Step responses the demonstrated a 10- μm resolution and 6-μm rms noise in the translational mode. This compact single-moving-part positioner is suitable for use in precision-positioning systems, e.g., in semiconductor manufacturing.