Multi-degree-of-freedom micropositioning using stepping principles

citizen of Austria accepted on recommendation of Prof. Dr. G. Schweitzer, examiner Prof. Dr. R.Y. Siegwart, co-examine

Alignment of microparts using force controlled pushing

In today’s and tomorrow’s development of new products, precise positioning and assembly of small parts is of fundamental importance. Often, such tasks require the alignment of objects with features such as edges or surface structures. In this work, we explore force controlled pushing of microparts on a planar substrate with a micromanipulator. The pushing tool is an AFM cantilever equipped with a piezoresistive force sensor. Its corse position, as well as the global manipulation strategy, is specified by the human operator. First, we present force measurements during typical pushing operations. Using these measurements, a sensor guided controller is implemented to maneuver the robot locally by detecting events such as hitting an obstacle or changing contact conditions. Using force/position macros, we are able to push the objects precisely to a desired location without exceeding a certain limit force. Experimental results demonstrate the ability of aligning microparts on a horizontal plane with micrometer accuracy relative to each other. For automated assembly applications there are two possibilities: the local controller presented in this paper can be integrated either in a passive global positioning system if the geometry of the problem is well defined. Conversely, a feedback system, e.g., with quantitative computer vision, can be used to cover a larger spectrum of object sizes and shapes

Inertial drives for micro- and nanorobots : analytical study

The need for high precision robots dedicated to the assembly of microsystems has led to the design of new kinds of actuators able to reach very high positional accuracy over large distances. Among these, inertial sliders have received considerable interest in the last years. They have the advantage of being based on a simple principle that leads to a simple mechanical design. However, because they are based on the nonlinearity of friction, it is not easy to predict their stepsize repeatability. In order to understand the most important parameters affecting the precision of inertial drives, a theoretical study of a 1 degree of freedom inertial slider has been established. Analytical formulas describing the influence of different parameters, such as static and dynamic friction and mass distribution, have been developed. The effect of applied functions (sawtooth and parabolic), have also been studied. The theoretical cut off frequency has been found for each of the different waveforms, allowing us to predict the maximal and minimal working frequencies of the system. Thus, for each curve form, the repeatability of inertial sliders can be evaluated taking into account the uncertainties in the friction coefficients. The best suited waveforms for given constraints can therefore be selected. Simulations carried out from this have been successfully compared to experimental results

High precision robots for automated handling of micro objects

Nanotechnology is a key issue in today’s and tomorrow’s 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”, ie automated handling of microparts with nanometer resolution. 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. It is then shown, that if a global sensor is used, measuring the relation gripper-object, the only requirement for the mechanical structure is a good resolution. Finally, two new 3 dof planar robot designs are presented. Both of them have unlimited range of motion while having a resolution down to 10 nm. One of them has been controlled using a vision feedback under a light microscope and showed very promising results