A Moving Magnet Actuator for Large Range Nanopositioning

In this paper, we present the design, fabrication, and testing of a moving magnet actuator (MMA) for large range (∼10mm) nanopositioning. MMAs are direct-drive, single-phase electromagnetic linear actuators that provide frictionless and backlashfree motion. These qualities, along with an adequate motion range, make MMAs promising candidates for large range nanopositioning. In this work, we identify actuatorand systemlevel performance criteria and associated design tradeoffs, and use this knowledge to systematically and concurrently design an MMA and a double parallelogram flexure bearing. The resulting actuator provides a force output per unit square root power of 4.56N/ √ W , better than 9% force uniformity with respect to stroke, and a low moving mass of 106g. An integrated thermal management system is also incorporated as part of the actuator in order to mitigate the heat dissipated from the MMA coils. The overall single-axis motion system was fabricated and tested to demonstrate a 36Hz open-loop bandwidth and less than 4nm (RMS) steady-state positioning noise over a 10mm motion range. Preliminary closed-loop design and testing highlight the potential of the proposed actuator in nanopositioning. INTRODUCTION AND MOTIVATION A moving magnet actuator (MMA) is a direct-drive, single phase, electromagnetic linear actuator. MMAs have been employed in the past in a wide range of applications including disk drives, automotive valves, and vibration isolators [1–3]. A commonly used MMA architecture is shown in Fig. 1, where an axially-oriented cylindrical permanent magnet sandwiched between two iron pole-pieces forms the mover. The stator consists of a back iron along with two oppositely wound coils con∗Corresponding Author ([email protected], 734-239-2928) N S