High Precision Robots for Automated Handling of Micro Objects


Alain Codourey, Zesch Wolfgang


Presented at the Sem. on Handling and Assembly of Microparts, Nov. 14, 1994, Vienna, AUT.


nanorobot, microrobot, micro assembly, precision mechanism


Nanotechnology is a key issue in todays and tomorrows development of advanced products. Soon new tools will be needed to automatically handle and assemble micro-sized objects with nanometer precision, or simply to give human beings the capability of operating in those tiny dimensions. Seeing emerging applications in this field, the Swiss Federal Institute of Technology at Zurich (ETHZ) decided to focus an interdisciplinary project on the theme Nanorobotics, i.e. automated handling of microparts with nanometer resolution, which started in 1993. The system is composed of a high precision robot operating under a light microscope. To achieve higher resolution a scanning electron microscope will be used in a later stage. A stereo vision module and some additional local sensors are used to control the robots position. The commands will be given by a human operator through a virtual reality-based user interface. In this paper, after a short description of the goals and the approach taken in this project, some important aspects of the design of high precision robots are stressed. It is especially shown that if a minimum of 6 independent degrees-of-freedom (dof) is required to freely position an object in space, redundant robots will lead to less complicated and more efficient mechanical structures. Since it is extremely difficult to mechanically achieve an accuracy in the nanometer range, a global measurement system is needed to correct for errors. If a fusion of global (vision), local and joint sensors is used, the only requirement for the mechanical structure is a good resolution. Finally, two new robot designs are presented. Both of them are 3 dof planar robots (x,y,q) but use different driving mechanism. The first one is based on an Inch-Worm-like principle with clamping and stepping on a flat surface. The second one operates with the inertial stepping principle. Both systems are based on piezoelectric actuators and can be used in 2 operating modes: fine motion and rough motion. The rough motion mode is used to travel over long distances making steps. The fine motion mode is used locally to achieve high resolution (< 10 nm) over a maximum range of 5 microns. These 2 robots have been controlled using a vision system under light microscope and showed good results.

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