Query: Robust design of selectively compliant flexure-based precision mechanisms

Candidate papers:

abstract: Acknowledgments I wish to thank a number of people who have helped me in my professional and personal development during my graduate studies at The University of Texas at Austin. Firstly, I would like to express my sincere gratitude to Prof. Raul G. Lon goria, who has been more than a mentor to me. His guidance, motivation, and support have been critical in all my accomplishments in graduate school. I would like to thank Prof. S. V. Sreenivasan, who helped me to overcome my weaknesses, by instilling discipline and confidence in my work. His professionalism and down to earth demeanor will always be inspirational to me. valuable suggestions in improving the dissertation. I would like to especially thank Dr. Choi and engineers at Molecular Imprints, namely, Pawan Kumar, and Mario Meissl, for their help with the experimental work included in the dissertation. Engineering, and the Office of Graduate Studies for financial support throughout my graduate education. v Finally, a special note of appreciation to my family members. To my beloved wife, Rashmi, whose many sacrifices, and unflinching support carried us through the travails and triumphs of higher education, I couldnt be more thankful. To my parents, for their patience, encouragement, and faith in me, Nano scale positioning and metrology are at the cutting edge of motion control technology, driven by ever increasing number of applications, including semiconductor fabrication, data storage, nano fabrication, biotechnology among others. In this 'very small range (few um) and very high precision (few nm) domain' flexure based mechanisms are the preferred means for the motion guiding systems, because of several exceptional properties like selective compliance, monolithic design, absence of friction, hysteresis, and wear. However, despite their numerous advantages, their motion characteristics are extremely sensitive to thermal variations, material property variations, machining tolerances among others. The geometric errors induced by machining process variations interact with the mechanism geometry, and lead to parasitic motion in directions other than the mechanism degrees of freedom. These errors cannot be completely eliminated by calibration, as they are coupled with the desired mechanism motion. vii This thesis focuses on the problem of parasitic motion in flexure based precision compliant mechanisms in the presence of geometric errors induced by machining tolerances. A spatial kinematics approach based on screw systems is used to model the compliance of the flexure mechanisms. The geometric errors induced by machining tolerances are systematically included in the modeling. The model not only determines the complete spatial
author_names: Chinmaya B Patil
title: Robust design of selectively compliant flexure based precision mechanisms
year: 2008

abstract: Preface INTRODUCTION COMPLIANCE BASED DESIGN OF FLEXURE HINGES Introduction Generic Mathematical Formulation Single Axis Flexure Hinges for Two Dimensional Applications Multiple Axis Flexure Hinges for Three Dimensional Applications Two Axis Flexure Hinges for Three Dimensional Applications Conclusions STATICS OF FLEXURE BASED COMPLIANT MECHANISMS Introduction Planar Compliant Mechanisms Spatial Compliant Mechanisms DYNAMICS OF FLEXURE BASED COMPLIANT MECHANISMS Introduction Elastic Potential Energy for Individual Flexure Hinges Kinetic Energy for Individual Flexure Hinges Free and Forced Response of Flexure Based Compliant Mechanisms Damping Effects FINITE ELEMENT FORMULATION FOR FLEXURE HINGES AND FLEXURE BASED COMPLIANT MECHANISMS Introduction Generic Formulation Elemental Matrices for Flexure Hinges Elemental Matrices for Rigid Links Application Example Appendix TOPICS BEYOND THE MINIMAL MODELING APPROACH TO FLEXURE HINGES Large Deformations Buckling Torsion of Noncircular Cross Section Flexure Hinges Composite Flexure Hinges Thermal Effects Shape Optimization Means of Actuation Fabrication APPLICATIONS OF FLEXURE BASED COMPLIANT MECHANISMS Macroscale Applications Microscale (MEMS) Applications
author_names: Nicolae Lobontiu
title: Compliant Mechanisms: Design of Flexure Hinges
year: 2002

abstract: Flexure joints are widely used to approximate the function of traditional mechanical joints, while offering the benefits of high precision, long life, and ease of manufacture. This paper investigates and catalogs the drawbacks of typical flexure connectors and presents several new designs for highlyeffective, kinematically behaved compliant joints. A revolute and a translational compliant joint are proposed (Figure 1) both of which offer great improvements over existing flexures in the qualities of (1) large range of motion, (2) minimal axis drift, (3) increased off axis stiffness, and (4) reduced stressconcentrations. Analytic stiffness equations are developed for each joint and parametric computer models are used to verify their superior stiffness properties. A catalog of design charts based on the parametric models is also presented, allowing for rapid sizing of the joints for custom performance. Finally, two multi degree of freedom joints are proposed as modifications to the revolute joint. These include a compliant universal joint and a compliant spherical joint, both designed to provide high degrees of compliance in the desired direction of motion and high stiffness in other directions.
author_names: Brian Trease

Yong Mo Moon

Sridhar Kota
title: DESIGN OF LARGE DISPLACEMENT COMPLIANT JOINTS
year: 2005

abstract: In this paper, a quantitative comparison is made between straight beam and curved beam flexures for application on selectively compliant mechanisms. Following a general procedure previously described in the literature, the closed form compliance equations for both flexural hinges are firstly derived. Then, the two morphologies are compared in terms of maximum achievable rotation and selective compliance (i.e. capability of providing low stiffness along a single desired direction) In particular, the performance of each design solution is quantified by means of purposely defined quality indexes, analytically computed on the basis of the hinges compliance matrix. Finally, the potentials of these types of flexures for the optimal design of compliant robotic fingers are critically discussed.
author_names: Giovanni Berselli

Farid Parvari Rad

Rocco Vertechy

Vincenzo Parenti-Castelli
title: Comparative evaluation of straight and curved beam flexures for selectively compliant mechanisms
venue: 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics
year: 2013

abstract: This paper introduces the iRobot Harvard Yale (iHY) Hand, an underactuated hand driven by five actuators that is capable of performing a wide range of grasping and in hand repositioning tasks. This hand was designed to address the need for a durable, inexpensive, moderately dexterous hand suitable for use on mobile robots. The primary focus of this paper will be on the novel simplified design of the iHY Hand, which was developed by choosing a set of target tasks around which the hand was optimized. Particular emphasis is placed on the development of underactuated fingers that are capable of both firm power grasps and low stiffness fingertip grasps using only the compliant mechanics of the fingers. Experimental results demonstrate successful grasping of a wide range of target objects, the stability of fingertip grasping, and the ability to adjust the force exerted on grasped objects using high impedance actuators and underactuated fingers.
author_names: Lael Odhner

Leif P Jentoft

Mark R Claffee

Nick Corson

Yaroslav Tenzer

Raymond R Ma

Martin Buehler

Robert C Kohout

Robert D Howe

Aaron M Dollar
title: A compliant, underactuated hand for robust manipulation
venue: Int. J. Robotics Res.
year: 2014

abstract: This paper presents the design and control of a novel gripper device with a passive type of compliant constant force mechanism. The function of constant force output is achieved by using the combination of a positive stiffness and a negative stiffness mechanism. The negative stiffness is generated by a bistable buckled fixed guided beam. Conventionally, when gripping a target object using a high stiffness gripper, both the displacement control and force control are required to prevent the damage of the object. The uniqueness of the developed constant force gripper is that it can eliminate the dependence on force control while keeping the force constant via its mechanical structure. The gripper performance is evaluated by the established analytical model and nonlinear finite element analysis, and validated through experimental study on a fabricated prototype. To achieve a precise position output of the gripper jaw, a discrete time variable structure control strategy based on a nonswitching type of reaching law is realized. The effectiveness of the gripper system is verified by conducting experimental studies on grasp hold release operations of a micro copper wire.
author_names: Yilin Liu

Yulong Zhang

Qingsong Xu
title: Design and Control of a Novel Compliant Constant Force Gripper Based on Buckled Fixed Guided Beams
venue: IEEE/ASME Transactions on Mechatronics
year: 2017

abstract: This paper presents a line element based approach to the topology synthesis of electrothermal compliant (ETC) mechanisms. A line element is a one dimensional model of the electrical, thermal, and elastic behavior of a beam like continuum. In contrast to topology synthesis of ETC mechanisms by a continuum element based approach, the line element based approach offers significant conceptual and practical advantages. The line element allows for straightforward modeling of surface heat transfer in the topology optimization framework. It also obviates the need to interpolate electrical and thermophysical properties in the topology synthesis procedure. Moreover, this approach results in clean geometries that are easy to fabricate directly in their optimized form. Solutions obtained from this procedure are compared with results from continuum based optimal synthesis procedures as well as intuitive designs reported in the literature. A number of design examples are used to demonstrate the ability of the procedure to generate nonintuitive topologies. The synthesis procedure is also used to study the influence of the direction of output and the electrical and thermal resistance of the workpiece on the resulting optimal topologies.
author_names: Nilesh D Mankame

G K Ananthasuresh
title: Topology synthesis of electrothermal compliant mechanisms using line elements
year: 2004

abstract: The consideration of compliant mechanisms as Microelectromechanical Systems (MEMS) is the focus of this research endeavor. MEMS are micron to millimeter devices that combine electrical, mechanical, and information processing capabilities on the same device. These MEMS need some mechanical motion or parts that move relative to each other. This relative motion, using multiple parts, is not desired because of the assembly requirement and the friction introduced. Compliant devices limits or eliminates friction and the need for multi component assembly. Compliant devices improve designs by creating single piece mechanisms. The purpose of this research is to validate surface micromachining as a viable fabrication process for compliant MEMS designs. Specifically, this research has sought to fabricate a micro compliant gripper and a micro compliant clamp to illustrate the process. While other researchers have created compliant MEMS, most have used comb drive actuation methods and bulk micromachining processes. This research focuses on fully compliant devices that use device flexibility for motion and actuation. Validation of these compliant MEMS is achieved by structural optimization of device design and functional performance testing. This research contributes to the ongoing research in MEMS by evaluating the potential of using surface micromachining as a process for fabricating compliant micro mechanisms.
author_names: Joe A Bradley
title: Design of Surface Micromachined Compliant MEMS
year: 2002

abstract: Robotic origami design allows creating meso scale robotic systems and mechanisms not limited by degrees of freedom, miniaturization and assembly downsides of conventional transmission mechanisms. However, unlike the traditional rigid approaches, robotic origami application has been limited by the complex deformation and kinematics of the compliant joints and actuation based on active materials or conventional electric motors. To generalize their application at meso scale requires a combination of the predictability of traditional rigid kinematics and the manufacturing flexibility of robotic origami. Here we present a study of conventional transmission mechanisms, including a slider crank and cam follower, made in quasi 2D form by selective machining and stacking of multiple layers of composite material with minimal assembly. Owing to a compliant design powered by low profile piezoelectric motors, our 5.3 mm thick and lightweight mechanisms transmit rotational motion to translational movements in and out of plane. We develop analytic models that we validate in terms of force and motion output on our prototypes.
author_names: Frederic Giraud

Zhenishbek Zhakypov

Jamie Kyujin Paik
title: Design of Low Profile Compliant Transmission Mechanisms
venue: 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
year: 2019

abstract: Abstract This paper presents the design, development, and control of a large range beam flexure based nano servo system for the micro stereolithography (MSL) process. As a key enabler of high accuracy in this process, a compact desktop size beam flexure based nanopositioner was designed with millimeter range and nanometric motion quality. This beam flexure based motion system is highly suitable for harsh operation conditions, as no assembly or maintenance is required during the operation. From a mechanism design viewpoint, a mirror symmetric arrangement and appropriate redundant constraints are crucial to reduce undesired parasitic motion. Detailed finite element analysis (FEA) was conducted and showed satisfactory mechanical features. With the identified dynamic models of the nanopositioner, real time control strategies were designed and implemented into the monolithically fabricated prototype system, demonstrating the enhanced tracking capability of the MSL process. The servo system has both a millimeter operating range and a root mean square (RMS) tracking error of about 80 nm for a circular trajectory.
author_names: Zhen Zhang

Peng Yan

Guangbo Hao
title: A Large Range Flexure Based Servo System Supporting Precision Additive Manufacturing
year: 2017