Stefano Bottinelli

Delta3: design and control of a flexure hinge mechanism

In the fields of micro positioning, micromanipulation and micro machining, the required motion precision is continuously increasing. The demand also increases for high dynamic performances (large bandwidth, high closed loop stiffness.). In many cases an inappropriate mechanical structure prevents to achieve these objectives. For example backlash or friction have to be reduced as much as possible. In this paper, we propose backlash-free and friction-free manipulators using flexure hinges and direct drive actuators. A three degrees of freedom (dof) parallel robot (X, Y, Z) that is a transposition in a flexible structure of the Delta robot kinematics is presented. We focus on the design and control of the robot. A simple dynamic model is proposed and compared with measurements. The system is characterized and we propose solutions to improve performances. These solutions are tested on a linear stage.

Fatigue failure of thin wire-electrodischarge-machined flexure hinges

This paper inquires into the exportability of the fatigue measurements made on standard test-specimen to wire electro- discharge machined flexures with thin cross sections (50 micrometers ). It describes the results of a set of fatigue measurements made on 66 circular flexible hinges machined in steel and bronze by wire electro-discharge machining. After reminding the fatigue theory and describing the theoretical model used to calculate the stresses inside the bent hinges, the paper describes the experimental setup and the measured results. The main conclusions drawn out of this work is that the admissible stresses for the tested flexures having a low surface roughness (Ra equals 0.2 micrometers ) are at least as high as the admissible stresses for standard test specimens. This indicates that fatigue data found in literature can be used to calculate the dimensions of this kind of flexures without any reduction of the safety factor.

XY-stage for alignment of optical elements in MOEMS

The alignment of optical elements in a Micro-Opto-Electro- Mechanical System, is of prime importance in order to realize a reliable and low loss system. Fabrication errors or temperature changes deteriorate the alignment accuracy. These errors can be compensated with the aid of an active alignment system. The aim of the paper is to investigate an active system in order to align microlenses and fibers. A high lateral precision is required for single mode fiber injection, typically better than 1 micrometers . The alignment along the optical axis is less critical. Our system consists of a microlens placed between one input fiber and one output fiber. The fibers are held in V-grooves and the microlens is mounted on an XY-stage. The lens is fabricated by melting resist technology and subsequent etching in quartz. The mechanical parts are realized by wire electro-discharge machining (wire-EDM). Two piezo-electrical actuators move the flexible bearings of the stage in the X and Y direction. We will present the results obtained with this system and we will discuss its potential.

Optical fiber switching device with active alignment

The alignment of optical elements in a MOEMS, is of prime importance in order to realize a reliable and low loss system. Fabrication errors or temperature changes deteriorate the alignment accuracy. These errors can be compensated with the aid of an active alignment system. The aim of the paper is to investigate an active system in order to align microlenses and fibers within a system. A high lateral precision is required for single mode fiber injection, typically better than 1 micrometers . With the active alignment system we can correct a misalignment of +/- 6 micrometers .