Precision Positioning down to Single Nanometres Based on Micro Harmonic Drive Systems

At present the Micro Harmonic Drive is the world’s smallest backlash-free micro gear. Its favourable properties like high repeatability, high torque capacity, low mass of inertia and high degree of efficiency are proved applied in different applications for semiconductor manufacturing, measuring machines, aerospace and other industries. However for high precise assembly applications often linear adjustments of a few nanometres are required. The common solution for positioning in the nanometres range is the use of piezoelectric effect actuators. The drawbacks are the need for a closed loop control system, overshooting during positioning, local wear, short travel ranges and loss of position without power supply. To overcome these obstacles the advantages of the Micro Harmonic Drive are exploited together with a stepper motor, an eccentric drive and monolithic flexure hinges are combined in a compact unit, called Nanostage. With this setup a travel range of 40 microns and a resolution < 3 nm is achieved. The single sided and double sided repeatability was measured in an open loop control system with < 5 nm and < 10 nm respectively.