Session: MR-07-04

Paper Number: 143466

143466 - An Application of the Stability Circle to the Design of MEMS Technology Based Systems With Floating Center Rotary Comb Drives 

In this article a known locus of second order path curvature in rigid plane motion is applied to the development of a procedure which guides designer to the choice of a suitable positioning of a floating center rotary comb drives (FCRCD) which can be embedded inside a MEMS-Technology based generic mechanism. 

In the first part of the paper, the new concept FCRCD is briefly described, by underlying its efficacy to improve the actuating torque in the embedding microsystem. In fact, FCRCD actuators have been conceived to increase the available input power that provides motion. Typical rotary comb drives require the relative motion of the two matching fingers arrays to be a rotation. This is not possible with a great accuracy becaus flexure hinges must be used at the microscale. Therefore, this paper addresses the problem of minimizing the deviations of the trajectories of the points belonging to the fingers attached to the coupler link from concentric circular arcs having the first order pole as their center.

The device that is the object of this investigation consists of a microgripper for biomedical applications (cell and tissue maipulation) and has been actually fabricated by using Deep Reactive Ion Etching (D-RIE) on Silicon-on-Insulator (SOI).
An accurate report of the particular adopted method has been described in details in a companion contribution.

More specifcally, the microgripper under analysis consists of two symmetric compliant mechanisms that are used to operate each jaw. Each compliant mechanism is synthesised starting by the PRBEM (Pseudo-Rigid Body Equivalent Mechanism) consisting of a four-bar linkage. The two compliant mechanism are then obtained by replacing the classical revolute joints with a CSFH hinge (Conjugate Suface Flexure Hinge) and so the former classic four-bar linkage represents the topology of the two lumped compliant mechanisms.

The second part of the paper will describe how the inflection circle can be used as an important tool to detect the most feasible or unfeasible zones where to place the FCRCD in the microsystem. Being only at the second order of the plane curve theory, the inflection circle is considered rather elementary a tool. Nevertheless, this paper  will show how such fundamental locus of the plane will be used to identify the critical region where a FCRCD should not be placed. The adopted method recalls very much the reasons why the inflection circle has been also referred to as stability circle.

Based on some simple well-known results in the field of kinematic analysis of planar rigid systems, this paper shows how it is possible to optimize a class of new microsystems based on MEMS technology that use electrostatic actuation enhanced by an additional new type FCRCD comb drive. The FCRCD (Floating Center Rotary Comb Drive) is a novel type of comb drive characterized by the fact that it acts directly on the coupler of the pseudo rigid part corresponding to a four-bar linkage coupler. 

While the fabrication process and its implication will be described in a forthcoming paper, the present contribution focus on 
theoretical concepts that provide a justification to the introduction of new design criteria, for this class of comb drive. It is demonstrated that the position of the interdigitated zone can be optimized in order not to allow fingers belonging to different arrays to get in contact, with consequent electrical discharge, pull-in or stitching of the device.

Hopefully, this article may exemplify how the convergence of two distinct fields of knowledge (MEMS Technology and Kinematic Analysis) can yield quite interesting outcomes.

 

 

Presenting Author: Nicola Pio Belfiore Roma Tre University

Presenting Author Biography: Nicola P. Belfiore, Professor, IEEE Member, teaches Applied Mechanics, Functional Design and Underwater Robotics at the University of Roma Tre, Italy. After the achievement of the Ph.D. degree, completed at Sapienza University of Rome, in cooperation with the University of Maryland of College Park, he was with Sapienza University from 1996 to 2000 as research fellow, and from 2001 to 2017 as Associate Professor. In October 2017 he moved from Sapienza to Roma Tre University, where he got the position of Full Professor in 2019.
In 1993 he won the AMR Best Paper Award at the Third National Applied Mechanisms and Robotics Conference (Cincinnati, OH) and in 1997 he also won the AMR Unique Contribution Award at the same Conference. In 2009 he won the Best Research Paper Award at the 18th Int. Workshop on Robotics in Alpe-Adria-Danube Region in Brasov, Romania. Since 2008 he is also a Honorary Professor of the Obuda University, Hungary. Author of three textbooks, four patents and about one hundred scientific papers he has been the coordinators of several scientific projects, both National and European. In 2013 he was the director of the 2nd Level Vocational Master in Energy Conversion Efficiency and Renewable Energy. From 2019 to 2022 he was nominated Head of the Degree Programs of Mechanical Engineering BSc and MSc in Mechanical Engineering, MSc in Aeronautical Engineering and BSc and MSc in Marine and Ocean Engineering, while in 2022 he was appointed as Deputy Director coordinator of the teaching activities of the Department of Industrial, Electronic and Mechanical Engineering. His actual interests are Topology, Kinematics and Dynamics of Mechanisms and Robots, MEMS and NEMS Design, Functional Design, and Tribology.

Authors:

Nicola Pio Belfiore Roma Tre University
Serena Coppola Roma Tre University
Alessandro Muccichini Roma Tre University
Cristiano Piroddi Roma Tre University
Matteo Verotti University of Genua