Modellierung und Regelung von Impact Drives für Positionierungen im Nanometerbereich

The progression of miniaturisation in technics and science demands new tools for very accurate positioning. These could be used in Biology, Chemistry or Medicine. Until now, processes can only be viewed through suitable microscopes. Tools for very accurate positioning allow the user to interact with these processes. The actuators in today's robots are usually DC-or stepper motors. They have to deal with the nonlinearity of friction. Therefore, it is difficult to attain highly accurate position control down to the nanometer scale. In this thesis, possible actuators and actuator principles for nanorobots will be discussed. The impact drive actuated by piezoelements is examinated in detail. To understand its behaviour, we firstly modelled the impact drive with a rigid body model. This led to analytical equations for the motion. To inspect its characteristics near the mechanical resonant frequency, a more accurate model, which contains the dynamic behaviour of the piezo¬ element, is established. It is shown, that impact drives actuated by piezoelements are able to operate with nanometer resolution in an infinite working ränge. The impact drive is controlled by dividing its motion into rough and fine manoeuvres. Rough motion is used for manoeuvres down to the micrometer scale using the impact principle. Fine motion provides a linear driving signal for the piezoelement in its working ränge and nanometer-resolution can then be reached. In order to extend the nanorobots manoeuvres to several degrees of freedom, suitable sensor configurations are discussed. This thesis, together with the work of the other PhD students in the ETH Nanorobotics Polyproject, was coordinated in order to construct a 5 degree of freedom robot. This robot contains the impact drive as its actuator principle, uses parallel kinematics and is controlled by a light microscope combined with vision processing algorithms.