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.
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.
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 .
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.
This paper describes a detailed study of the behavior of the parallel spring stage having four circular flexure hinges of very thin cross-sections manufactured by wire electro- discharge machining. The state of the art recalls the abundant literature published on the parallel leaf spring stage, and presents the few articles found dealing with the parallel spring stages. The theoretical modeling for the calculation of the linear stiffness of the parallel spring stage is described. The starting point of the discussion is the observation that the theoretical model which is valid when applied to stages of large dimensions produces large errors when applied to wire-EDM machined flexures of very thin cross-sections. As an explanation of this observation, a hypothesis is put forward: on the surface of each neck a thin layer affected by the EDM process is not playing any mechanical role in the bending of the flexure and the thickness of this layer is related to the roughness of the surface. The experimental results show that the hypothesis is true to a large extent but that roughness is probably not the only factor affecting the neutral zone. The 'white layer' and the microstructural homogeneity of the material used could also be determinant.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.