Design and test of a compact compliant gripper using the Scott-Russell mechanism

This paper presents the design, modeling, fabrication, and test of a monolithic compliant gripper for micro-manipulation applications. A compact compliant mechanism that enables in-principle straight-line parallel jaw motion is obtained, by combining the Scott-Russell mechanism and the parallelogram mechanism. The right-circular corner-filleted (RCCF) flexure hinge is adopted to achieve a large displacement of lumped-compliance joints. A pseudo-rigid-body model (PRBM) method with the help of the virtual work principle is performed to obtain parametric analytical models including the amplification coefficient and kinetostatics. Finite element analysis (FEA) is conducted to validate the analytical model and capture adverse parasitic motions of jaws. A monolithic prototype was fabricated, the test results of which show satisfactory performances

General design equations for the rotational stiffness, maximal angular deflection and rotational precision of various notch flexure hinges

Notch flexure hinges are often used as revolute joints in high-precise compliant mechanisms, but their contour-dependent deformation and motion behaviour is currently difficult to predict. This paper presents general design equations for the calculation of the rotational stiffness, maximal angular elastic deflection and rotational precision of various notch flexure hinges in dependence of the geometric hinge parameters. The novel equations are obtained on the basis of a non-linear analytical model for a moment and a transverse force loaded beam with a variable contour height. Four flexure hinge contours are investigated, the semi-circular, the cornerfilleted, the elliptical, and the recently introduced bi-quadratic polynomial contour. Depending on the contour, the error of the calculated results is in the range of less than 2% to less than 16% for the suggested parameter range compared with the analytical solution. Finite elements method (FEM) and experimental results correlate well with the predictions based on the comparatively simple and concise design equations

detasFLEX – A computational design tool for the analysis of various notch flexure hinges based on non-linear modeling

Notch flexure hinges are commonly used in compliant mechanisms for precision engineering applications and yet important rotational properties of a hinge like the bending stiffness, maximum angular deflection and rotational precision are difficult to predict accurately and simultaneously. There exist some closed-form equations and a few design tool approaches for calculating flexure hinges with particular geometries, but apart from that no comprehensive calculation program for the contour-specific analysis is known to the authors. Developed in MATLAB, this paper presents a novel computational design tool using a non-linear analytical approach for large deflections of rod-like structures to calculate the elasto-kinematic flexure hinge properties by numerically solving a system of differential equations. Building on previous investigations, four certain hinge contours are implemented, the circular, the corner-filleted, the elliptical, and the power function-based contour with different exponents. In addition to the theoretical approach and the implementation it is exemplarily shown, that finite elements method (FEM) results correlate well with the analytical design tool results. For a given deflection angle of 10° and a corner-filleted contour as an example, the deviations of the bending stiffness are between 0.1&thinsp;% and 9.4&thinsp;% for typical parameter values. The presented design tool can be beneficial for the accelerated and systematic synthesis of compliant mechanisms with optimized flexure hinges.</p

detasFLEX - a computational design tool for the analysis of various notch flexure hinges based on non-linear modeling

A novel computational design tool to calculate the elasto-kinematic flexure hinge properties is presented. Four hinge contours are implemented. It is shown, that FEM results correlate well with the analytical design tool results. For a given deflection angle of 10° and a corner-filleted contour, the deviations of the bending stiffness are between 0.1 % and 9.4 %. The design tool can be beneficial for the accelerated and systematic synthesis of compliant mechanisms with optimized flexure hinges

Étude d'un concept innovant d'actionneur électromécanique linéaire à effets magnétique et piézoélectrique en vue d'applications dans le domaine des commandes de vol

La généralisation des actionneurs électromécaniques dans les systèmes embarqués (commandes de vol, freins électriques ...) requiert le développement de nouvelles technologies dotées de performances et de fonctionnalités étendues. Dans ce contexte, la présente thèse vise à élaborer une solution innovante d'actionneur électromécanique linéaire à densité d'effort élevée. Cette solution est caractérisée par la combinaison d'effets magnétiques et piézoélectriques, permettant d'obtenir l'entraînement par contact d'une charge mobile. À partir de considérations théoriques relatives à chacune des fonctions élémentaires mises en jeu dans l'actionneur (blocage et entraînement), une architecture simple est proposée. Celle-ci est modélisée et validée à l'aide d'une maquette spécifique. Les premières expérimentations mettent en évidence la nécessité d'un dispositif permettant d'amplifier les déformations élémentaires produites par l'effet piézoélectrique. Une structure d'amplification à pivots flexibles est alors étudiée. Un modèle analytique de son comportement élastique est élaboré en vue de son dimensionnement et de son intégration au sein de l'actionneur. L'association du concept proposé à une stratégie d'alimentation spécifique permet enfin de caractériser expérimentalement un démonstrateur d'actionneur linéaire direct magnéto-piézoélectrique travaillant en mode quasi-statique. ABSTRACT : The generalisation of electromechanical actuators in onboard systems (fly-bywire systems, electric brakes...) requires the development of new technologies in order to provide better performances or functionalities. In this context, the present thesis aims to study an innovating solution of an electromechanical linear actuator with high density of force. This solution combines magnetic and piezoelectric effects to drive a mobile load by contact. From theoretical considerations of each elementary function of the actuator (blocking and drive), a simple architecture is proposed. An amplification structure with flexible hinges is also studied, dimensioned and integrated within the actuator. Thanks to a specific strategy of power supply, a demonstrator of a direct magnetopiezoelectric linear actuator, working in quasi-static mode, is then characterised in experiment